1077. Separating FID and Echo Contribution in Pass-Band BSSFP FMRI with Multiple-Phase Angle Cycling
Sung-Hong Park1,2, Tae Kim1, Ping Wang1, Timothy Q. Duong2, Seong-Gi Kim1
1Radiology, University of Pittsburgh, Pittsburgh, PA, United States; 2Research Imaging Institute, Ophthalmology/Radiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
We acquired high resolution multiple phase-cycled bSSFP fMRI datasets in rat brains at 9.4T and separated FID and main echo components based on Fourier analysis. The FID component showed stronger fMRI signals than the main echo component, but it showed stronger correlation with both intracortical veins and cortical surface veins. The fMRI signal from the main echo component could contribute up to half of that from the FID component, implying that the main echo component should not be neglected in interpreting pass-band bSSFP fMRI signals.
1078. A Novel Multi-Echo FMRI Weighting Strategy Using Principal Component Analysis for BOLD Contrast Sensitivity Enhancement
Mark Chiew1,2, Simon James Graham1,2
1Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; 2Rotman Research Institute, Toronto, Ontario, Canada
The use of multi-echo imaging techniques for contrast enhancement in BOLD fMRI is gaining momentum, particularly in real-time fMRI applications. A novel method is presented for combining multi-echo signals in weighted summation using principal component analysis (PCA) derived weights. The method is evaluated on human volunteers performing a simple motor task at 1.5 T, and is compared to other reported weighting schemes. The data driven PCA weighting method is demonstrated to produce time-series that achieve high relative contrast-to-noise ratio gain, without requiring additional data collection.
1079. Variable Density Spiral FMRI
Catie Chang1, Gary Harold Glover1
1Electrical Engineering & Radiology, Stanford University, Stanford, CA, United States
We propose a novel variable-density (VD) spiral k-space trajectory for brain fMRI. The trajectory consists of an Archimedean spiral from the origin out to an arbitrary radius k1, extending beyond k1 with a spiral in which the sampling density decreases as the k-space radius increases. Thus, it allows for a reduction in readout time at the expense of undersampling only high spatial frequencies. We implemented the VD spiral in a single-shot 2D spiral-in/out sequence for high (128x128) resolution, and demonstrate improved activation in a sensory-motor task compared to conventional (fully Archimedean) single-shot and interleaved sequences.
1080. High Resolution BOLD FMRI Using MHASTE
Yongquan Ye1, Yan Zhuo1, Xiaohong Joe Zhou2
1State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics,CAS, Beijing, China; 2University of Illinois Medical Center, Chicago, IL, United States
High resolution BOLD fMRI data on visual cortex were acquired using mHASTE, a novel GRAPPA accelerated single shot TSE technique, and the results were compared with those of GE- and SE-EPI. Higher SNR was obtained with mHASTE than both EPIs, and increased functional activation was detected by mHASTE but not by EPI when going from low resolution to high resolution. mHASTE was also found to have greater activation than both EPI in some cases,especially at high resolution, suggesting a more robust BOLD contrast mechanism for mHASTE in high resolution fMRI.
1081. Functional Magnetic Resonance Imaging Using PROPELLER EPI
Martin Krämer1, Thies Halvor Jochimsen1, Marc Roth1, Jürgen Rainer Reichenbach1
1Medical Physics Group, Department of Diagnostic and Interventional Radiology, Jena University Hospital, Jena, Germany
A method to improve spatial and temporal resolutions in fMRI using PROPELLER-EPI. First results are shown which demonstrate that a sliding window reconstruction of high resolution long-axis propeller (LAP) data is suitable for simple fMRI experiments. Additionally the results achieved by the LAP measurements are compared to the standard 64x64 EPI sequence which is usually used in fMRI. From there it is shown that the activation maps created from the LAP scans are better localized along the cortex.
1082. Passband BSSFP: Functional Contrast Compared to GRE-EPI and SE-EPI at 3T.
Pål Erik Goa1, Anders Kristoffersen1, Michael H. Chappell2, Rob H. Tijssen3, Asta K. Håberg4, Karla L. Miller3
1Dept. of Medical Imaging, St. Olavs University Hospital, Trondheim, Norway; 2Dept. of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), Trondheim, Norway; 3FMRIB Centre, Oxford University, Oxford, Oxon, United Kingdom; 4Dept. of Neuromedicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
The functional contrast in passband balanced steady-state free precession (pbSSFP) with 3D segmented EPI readout is compared to that of GRE-EPI and SE-EPI at 3T. For pbSSFP, TR is varied from 6.5 ms to 45 ms. Standard flickering checkerboard paradigm is used. We find that the best functional contrast is obtained at TR = 33 ms with corresponding EPI-factor of 40. At this TR, the functional contrast in pbSSFP is approximately half that of GRE-EPI and twice that of SE-EPI with otherwise comparable scan parameters. False detections due to banding artefacts are present in pbSSFP.
1083. Isotropic Sub-Millimeter FMRI in Humans at 7T
Robin Martin Heidemann1, Dimo Ivanov1, Robert Trampel1, Joeran Lepsien1, Fabrizio Fasano2, Josef Pfeuffer3, Robert Turner1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 2Fondazione Santa Lucia, Rome, Italy; 3Siemens Healthcare Sector, Erlangen, Germany
For isotropic high resolution fMRI at ultra-high field strength, susceptibility effects and T2* decay must be properly addressed. A combination of reduced FOV imaging (zoomed imaging) and parallel imaging is optimized here, achieving acceleration factors of up to 5.5. The high acceleration reduces distortions and image blurring, while incurring no other image artifacts. With this approach, high quality single-shot EPI acquisitions can be obtained with an isotropic resolution of 0.65 mm and sufficient coverage for e.g. fMRI in the visual cortex of the human brain.
1084. Automatic Functional and Anatomical Registration for FMRI Using Optimized 3D Flyback Echo Planar Imaging
Thomas Sushil John1, Michael Lustig2,3, John Mark Pauly2
1Electrical Engineering , Stanford University, Stanford, CA, United States; 2Electrical Engineering, Stanford University, Stanford, CA, United States; 3Electrical Engineering and Computer Science, UC Berkeley, Berkeley, CA, United States
Echo planar imaging (EPI) is the most widely used method for functional MRI. However, functional images are often distorted because EPI is highly sensitive to field inhomogeneities, eddy currents, and gradient delays. Functional and neuro-anatomical registration is complicated by these distortions and by the fact that functional and anatomical images are usually obtained with different imaging sequences. This work investigates the use of an optimized 3D flyback EPI trajectory with echo time shifting to obtain functional and anatomical images that have minimal distortions and are inherently co-registered.
Kimberly Brewer1,2, James Rioux1,2, Martyn Klassen3, Chris Bowen1,4, Steven Beyea1,4
1Institute for Biodiagnostics (Atlantic), National Research Council of Canada, Halifax, Nova Scotia, Canada; 2Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada; 3Robarts Research Institute, University of Western Ontario, London, Ontario, Canada; 4Physics and Atmospheric Science, Radiology and Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
Spiral pulse sequences are commonly used in fMRI, and spiral-in is known to be considerably better than spiral-out at signal recovery in regions with strong susceptibility field gradients. Previously proposed theories in the literature do not address the probability of signal displacement or fully explain all of the differences in signal recovery between spiral-out and spiral-in. In the current work we demonstrate that the difference in image intensity is not due to differences in signal displacement between spiral-in and spiral-out, but rather the increased phase coherence of the displaced pixels when using spiral-in.
John M. Ollinger1, Andrew L. Alexander1
1Waisman Laboratory for Brain Imaging, University of Wisconsin, Madison, WI, United States
A model for image variance due to motion is developed and validated. It can be used minimize motion effects by optimizing EPI sequence parameters. In general, variance is minimized by minimizing the partial derivative of the steady-state magnetization along the slice axis. In particular, sidelobes contribute much of the noise at high flip angles; an optimum flip angle exists for a specified degree of motion and can be computed; and inter-slice gaps increase variance due to motion rather than decrease it.
1087. Quantitative Evaluation of FMRI Acquisition Strategies at 7T Using NPAIRS
Robert L. Barry1,2, J Christopher Gatenby1,2, Allen T. Newton1,2, Stephen C. Strother3,4, John C. Gore1,2
1Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States; 2Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States; 3Rotman Research Institute of Baycrest, Toronto, ON, Canada; 4Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
Although 2D single-shot EPI is common in BOLD fMRI, recent studies have suggested that 3D multi-shot sequences such as PRESTO-SENSE may offer superior BOLD CNR through improved temporal efficiency. A four-way comparison was performed between 2D and 3D acquisition sequences at two voxel resolutions (1.19x1.19x2 mm3 and 2.19x2.19x2 mm3) at 7T. The quality of fMRI data was evaluated via independent and unbiased metrics of prediction and reproducibility using NPAIRS. Results suggest that EPI provides higher prediction and reproducibility for this study. Future work will investigate within-subject optimization, and further compare EPI with PRESTO-SENSE for an fMRI study requiring whole-brain coverage.
1088. The Effect of Parallel Imaging on the Sensitivity of BOLD Signal to Physiological Noise
Tomas Jonsson1, Tie-Qiang Li1
1Department of Medical Physics, Karolinska University Hospital, S-141 86, Stockholm, Sweden
The sensitivity to physiological noises of the reconstructed BOLD MR images is altered by the employed parallel imaging strategies. In this study, we mapped and compared the physiological noise sensitivity of BOLD fMRI data acquired with and without employing parallel imaging at two different spatial resolutions. Using higher spatial resolution reduces the signal strength and the relative sensitivity to physiological noise. This can be of SNR advantage particularly for time series fMRI data acquired at higher magnetic field.
1089. Multi-Slice Two- And Four-Fold Acceleration with Single- And Eight-Channel Coils, Respectively
Andrzej Jesmanowicz1, Shi-Jiang Li1, James S. Hyde1
1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States
Complex-valued tailored pulses have been used in an EPI sequence to excite two or more slices in human brain using a whole-brain transmit coil. One or more members of a receive-coil array have been used to acquire multi-channel image data. Complex-valued coil profiles have been used to recover slices, and parallel image formation has been demonstrated. Acceleration by a factor of 4 has been achieved with an eight-channel head coil.
1090. Detecting Single Cortical Column Activation Under Super High Spatial Resolution at 9.4 T Using Single-Shot Half K-Space GR-EPI
Rupeng Li1, Patrick Hettinger2, Younghoon Cho1, Christopher P. Pawela1, Ji-Geng Yan2, Andrzej Jesmanowicz1, Anthony Hudetz3, Hani Matloub2, James Hyde1
1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States; 2Plastic Surgery, Medical College of Wisconsin, Milwaukee, WI, United States; 3Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States
Single-shot half k-space GR-EPI sequence was used to push the BOLD imaging resolution to 300 micron cubic voxel and unique single column cortical activation in the sensory cortex was detected when stimulating the middle phalange of all 8 digits of rat.
1091. Development and Evaluation of Alternative Imaging Methods for FMRI at 7 Tesla
John Sexton1,2, Jascha Swisher3, Frank Tong3, Baxter Rogers1,2, J Christopher Gatenby1,4, John C. Gore1,4
1Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; 2Biomedical Engineering, Vanderbilt University, Nashville, TN, United States; 3Psychology, Vanderbilt University, Nashville, TN, United States; 4Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States
We compare single-shot gradient-echo 2D-EPI, multi-shot gradient-echo 3D-FFE and multi-shot gradient-echo 3D-PRESTO in a polar angle retinotopic mapping experiment at four isotropic resolutions (1.12mm3, 1.67mm3, 2mm3, and 3mm3) at 7 Tesla. Retinotopic maps in agreement with literature were obtained at all resolutions. The 3D sequences provided similar BOLD sensitivity and significantly less distortion compared to 2D-EPI. In addition, 3D-PRESTO provided much higher temporal resolution than 2D-EPI. Our findings suggest rich potential for high-resolution 3D imaging sequences in retinotopic mapping and other functional MRI experiments at high field.
Karsten Mueller1, Toralf Mildner1, Tom Fritz1, Joeran Lepsien1, Christian Schwarzbauer2, Harald E. Möller1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 2Aberdeen Biomedical Imaging Centre, University of Aberdeen, United Kingdom
To present auditory stimuli in the absence of scanner noise, the sparse temporal sampling (STS) approach was introduced. The interleaved-silent steady-state (ISSS) technique is combining the idea of splitting image acquisition and stimulus presentation with a better sampling of the fMRI signal. We performed an auditory experiment with pleasant and unpleasant stimuli using four fMRI sessions: STS, ISSS, and simultaneous stimulus presentation and image acquisition with axial and sagittal scanning. The total acquisition time was the same in all four sessions. The best sensitivity for detecting activations of sub-cortical regions (such as the amygdala) was found for ISSS.
1093. Feasibility of BOLD Magnetic Resonance Imaging of Lung Tumors at 3T
Qing Yuan1, Yao Ding1, Rami R. Hallac1, Paul T. Weatherall1, Robert Doug Sims1, Thomas Boike2, Robert Timmerman2, Ralph P. Mason1
1Radiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, United States; 2Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, United States
It is expected that BOLD MRI should be sensitive to tumor vascular oxygenation. In lung tumors BOLD MRI is challenging due to potential image artifacts from motion, blood flow, and susceptibility. The goal of this preliminary study was to optimize the BOLD imaging technique at 3T in patients with untreated lung cancer. A respiratory-gated multi-echo gradient-echo technique is demonstrated as a feasible method to quantify T2* values of lung tumors. The response of tumor T2* measurements to an oxygen-breathing challenge should be sensitive to tumor hypoxia and could therefore serve as a prognostic indicator before therapy.
1094. Interleaved T1- And T2*-Weighted Imaging Can Evaluate Dynamic Oxygen Challenge: A Feasibility Study
Yao Ding1, Ralph P. Mason1, Qing Yuan1, Rami R. Hallac1, Roderick W. McColl1, Robert D. Sims1, Paul T. Weatherall1
1Radiology, UT southwestern medical center at Dallas, Dallas, TX, United States
The present 2D respiratory-triggered interleaved T1- and T2*-weighted sequence provides a promising means to study TOLD and BOLD response simultaneously without the need for registration and with good temporal resolution (less than 30 seconds).
1095. Does the BOLD Response to EPI-Related Acoustic Noise Change Over an FMRI Experiment?
Oliver Hinds1, Aaron Hess2, M. Dylan Tisdall3, Todd Thompson1, Hans Breiter3, André van der Kouwe3
1A. A. Martinos Imaging Center at the McGovern Institute, Massachusetts Institute of Technology, Cambridge, MA, United States; 2Human Biology, University of Cape Town, Cape Town, South Africa; 3A. A. Martinos Center for Biomedical Imaging, Department of Radiology, MGH, Harvard Medical School, Charlestown, MA, United States
If the BOLD response to EPI acoustic noise changes over the time course of a standard fMRI experiment, both Type I and Type II errors can be made in fMRI group analysis. We used a pulse sequence based on single-voxel functional spectroscopy to silently measure the BOLD response induced by EPI-like scanner noise over about 40 minutes. No significant habituation or facilitation with respect to the scanner noise was found over that time. This result eliminates a possible confound for auditory and speech neuroimaging studies, especially those involving learning.
1096. Reproducibility of FMRI Localisation Within the Human Somatosensory System.
Rishma Vidyasagar1, Laura M. Parkes2,3
1MARIARC, University of Liverpool , Liverpool, Merseyside, United Kingdom; 2School of Cancer and Imaging Sciences, University of Manchester; 3Biomedical Imaging Institute, University of Manchester, Manchester, United Kingdom
fMRI data can often be affected by issues such as registration and scanner system errors. These issues affect interpretation of data and is especially relevant in longitudinal studies depending on accurate reproducibility of data. This study compared different analysis techniques of fMRI data to establish the most accurate means of overcoming these issues by focusing on fMRI data from the somatosensory system in the human brain.
1097. Real Time FMRI – Avoiding Drift Using Answer Blocks
Thomas WJ Ash1, T Adrian Carpenter1, Guy B. Williams1
1Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom
Where real time fMRI needs solely a digital (e.g., task vs rest or task 1 vs task 2) output, answer blocks can provide a means of circumventing the drift that is known to affect results. Using answer blocks, we improve performance compared to averaging over a block using classifiers from 53% to 84%, and using ROI techniques from 53% to 64%. This also gives a means for presenting probabilistic outputs to class membership, which are vital when dealing with impaired patients, for whom this kind of technique may be their only communication channel.
Jan Mehnert1,2, Christoph Schmitz2,3, Harald E. Möller1, Hellmuth Obrig1,2, Karsten Müller1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 2Berlin Neuroimaging Center, Charité University Hospital Berlin, Berlin, Germany; 3NIRx Medizintechnik GmbH, Berlin, Germany
Correlation analysis of low-frequency fluctuations in blood-oxygen level dependent (BOLD) fMRI data is known to yield functional connectivity maps. The procedure, also referred to as ‘resting-state connectivity’, has previously been applied to optical tomography (OT) data using dense probe arrays. Here, we assess whether a sparser topographical sampling still yields results that are comparable to the ‘gold standard’ of resting-state network assessment, i.e. fMRI. In a first step, we used a subset of optical fibers (2-3cm inter-optode distance) covering both motor cortices and combined OT with concurrent fMRI measurements to cross-validate our resting-state data analysis.
1099. High Resolution Functional MR Venography with 7T MRI
Seo-Hyun Lee1, Chang-Ki Kang1, Chan-A Park1, Young-Bo Kim1, Zang-Hee Cho1,2
1Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea, Republic of; 2Department of Radiological Sciences, University of California, Irvine, Irvine, CA, United States
MR venography using susceptibility weighted imaging (SWI) has been utilized for the study of venous morphology and the venous vasculature in disease states. However, SWI has poor intrinsic temporal resolution, thus it is not able to provide information on high temporal dynamic changes within a few seconds that occur during neural stimulation. In this paper, we proposed a technique, which we labeled functional MR venography (fMRV), to investigate the venous dynamic response to external stimulation using 7T MRI. The presented result suggests that this technique may provide important, more precise information regarding the venous response and its role in the overall hemodynamic response to neural activity with high spatial (0.5 isotropic) and temporal (3 seconds) resolution.
1100. The Orbitofrontal FMRI Experiment with Correction of the Susceptibility Artifact
Sung Suk Oh1, SungDae Yun1, Bumseok Jeong2, HyunWook Park1
1Department of Electrical Engineering, KAIST, Daejeon, Korea, Republic of; 2Department of Psychiatry, Eulji University Hospital, Daejeon, Korea, Republic of
The signal loss by the susceptibility artifact makes it difficult analyze the fMRI data of the orbitofrontal region of the brain. In addition, an EPI sequence, which is used in many fMRI experiments, has the geometric distortion and Nyqust ghosts. For the fMRI experiment with correction of these artifact and distortion, we used a flat RF pulse which provides nearly constant signal intensity against the magnetic susceptibility and a gradient echo sequence. In the result, it is shown that the signal loss in the orbitofrontal region of the brain is recovered without geometric distortion and Nyqust ghosts and the activation in that region was analyzed successfully.
Peter Dechent1, Rafael Polania2, Carsten Schmidt-Samoa1, Walter Paulus2, Andrea Antal2
1MR-Research in Neurology and Psychiatry, University Göttingen, Göttingen, Germany; 2Department of Clinical Neurophysiology, University Göttingen, Göttingen, Germany
Anodal/cathodal tDCS have facilitatory/inhibitory effects, respectively, on the stimulated cortical networks. Here we used concurrent tDCS-fMRI to test whether anodal/cathodal tDCS result in BOLD-fMRI signal changes during a resting condition. Furthermore, we examined tDCS-effects on brain activation during voluntary finger tapping. Anodal/cathodal tDCS over left M1 induced no detectable BOLD signal change. However, anodal/cathodal tDCS combined with finger tapping resulted in a decreased BOLD response in SMA, but not M1, in comparison to voluntary finger tapping without stimulation. This suggests that in contrast to the rest condition the combination of neuronal polarization and motor activation induces inhibition in remote brain areas.
1102. High-Resolution Fingersomatotopy at 7T Using HGS-Parallel Technique
SungDae Yun1, Jun-Young Chung2, Hyo Woon Yoon3, Zang-Hee Cho3, HyunWook Park1
1Department of Electrical Engineering, KAIST, Daejeon, Korea, Republic of; 2Neuroscience Research Institute, Gachon University of Medicine and Science , Incheon, Korea, Republic of; 3Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea, Republic of
In a high field MRI, improvements in SNR and image quality are very noticeable, even though there are some drawbacks such as increased field inhomogeneity and relatively short T2*. For EPI-based methods, these drawbacks are major challenges in performing fMRI. To reduce such problems, we employed the HGS-Parallel technique as an fMRI imaging method which used the conventional gradient echo. This sequence is relatively robust to field inhomogeneity and the T2* decay than the EPI. With the HGS-Parallel technique, we performed an fMRI experiment at a 7T for mapping the finger somatosensory area in a high quality and resolution form.
1103. Effectiveness of Mental Imagery Strategy in Controlling an Activation of the Left Middle Frontal Gyrus: Biofeedback Study Based on the Real-Time FMRI
Mikhail Zvyagintsev1,2, Yury Koush3, Miriam Dyck3, Klaus Mathiak3
1IZKF, RWTH Aachen University, Aachen, NRW, Germany; 2Psychiatry, RWTH Aachen University, Aachen, NRW, Germany; 3Psychiatry, RWTH Aachen University, Germany
Biofeedback based on a real-time fMRI is a promising tool especially in clinical research. In this study we show feasibility of controlling the left middle frontal gyrus by using mental imagery strategy.
1104. Sensitivity and Spatial Specificity of Multiple Phase-Cycled Pass-Band BSSFP FMRI at 9.4T
Sung-Hong Park1,2, Tae Kim1, Ping Wang1, Timothy Q. Duong2, Seong-Gi Kim1
1Radiology, University of Pittsburgh, Pittsburgh, PA, United States; 2Research Imaging Institute, Ophthalmology/Radiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
We performed high-resolution pass-band bSSFP fMRI at multiple phase cycling angles on rat brain at 9.4T. Activation foci in fMRI maps shifted as a function of phase cycling angle and the location of the foci was correlated with hyperintense regions in corresponding baseline transition-band bSSFP, some of which were also correlated with cortical surface veins or intracortical veins. The results indicated that there is spatial heterogeneity in signal sources (T2 or T2*) of pass band bSSFP fMRI. Baseline transition band bSSFP could be used to predict outcomes of corresponding pass-band bSSFP fMRI maps.
1105. Interleaved TMS/CASL: State Dependence of Repetitive TMS Effects on the Dorsal Premotor Cortex
Marius Moisa1, Rolf Pohmann1, Hartwig Roman Siebner2, Axel Thielscher1
1Max Planck Institute for Biological Cybernetics, Tübingen, BW, Germany; 2Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark
We have recently demonstrated the technical feasibility and the potential advantages of combining transcranial magnetic stimulation (TMS) with continuous arterial spin labeling (CASL) imaging. Here, we use this novel approach to assess the effects of repetitive TMS applied to the left dorsal premotor cortex (PMd) on rCBF (regional cerebral blood flow) during different motor states. The state-dependent effects of left PMd rTMS on rCBF, is in concordance with previous results using BOLD imaging and a different task. As a next step, we will analyze the time dependence of the observed TMS effects across the different experimental blocks of one run.
1106. Development of Simulator Training to Reduce Head Motion Artifact in FMRI
Shawn Ranieri1,2, Shaun Boe3, Fred Tam1, Lauren Gordon4, Tara Dawson1, Jon Ween5, William McIlroy6, Simon J. Graham1,7
1Rotman Research Institute, Baycrest Centre for Geriatric Care, Toronto, ON, Canada; 2Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada; 3Toronto Rehabilitation Institute, Toronto, ON, Canada; 4Faculty of Health Sciences, Queen's University, Kingston, ON, Canada; 5Kunin-Lunenfeld Applied Research Unit , Brain Health Complex, Toronto, ON, Canada; 6Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada; 7Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
There has been a longstanding need to develop techniques that improve data quality in fMRI by suppressing motion artifact. Head motion exceeding a few millimetres remains problematic and high interest participants including motor stroke patients often exceed this threshold. Here, a new technique is described that attempts to reduce participant head motion through visual feedback training in an fMRI simulator. Results from three stroke patients show that simulator training had a significant effect in suppressing head motion: (1) 11.25 mm before, 0.83 mm after; (2) 1.63 mm before, 0.67 mm after; (3) 4.47 mm before, 0.51 mm after.
1107. Scan Time Reduction in FMRI Using a 32 Channel Phased Array Receive Coil
Christina Triantafyllou1,2, Sheeba Arnold1, Steven Shannon1, John Gabrieli3, Susan Whitfield-Gabrieli3
1A.A. Martinos Imaging Center, McGovern Institute for Brain Research, MIT, Cambridge, MA, United States; 2A.A. Martinos Center for Biomedical Imaging, Department of Radiology, MGH, Charlestown, MA, United States; 3Department of Brain and Cognitive Sciences, MIT, Cambridge, MA, United States
Long durations in fMRI are typical, but that is unfeasible for specific populations. Scan-time reduction is possible if one could capitalize on the increased sensitivity afforded by high field strength or multiple channel phased arrays in the high-resolution regime. We evaluated this using a 32-channel coil at 3T with the n-back task on 18 subjects. Compared to 12-channel coil, working memory activation was significantly more (paired t-test) with two-thirds of the 32-channel data. Combination of 32-channel coil and high-resolution could imply lesser sample size, prevent additional data collection and enable studies that would otherwise be impossible due to time restrictions.
Lindsay Cherpak1,2, Kimberly Brewer1,2, Jodie Gawryluk1,3, Nicole Pelot1,2, Chris Bowen1,4, Ryan D'Arcy1,3, Steven Beyea1,4
1Institute for Biodiagnostics (Atlantic), National Research Council of Canada, Halifax, Nova Scotia, Canada; 2Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada; 3Psychology, Dalhousie University, Halifax, Nova Scotia, Canada; 4Physics and Atmospheric Science, Radiology and Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
This study involved a comprehensive evaluation of commonly-used techniques like EPI and spiral-out, as well as techniques designed to recover signal in SFG regions using BOLD methods (spiral-in, spiral-in/out, spiral-in/in and ASE spiral) and non-BOLD methods (FAIR and spin-echo spiral-in/out) at 4.0 T. A cognitive task used to evaluate temporal lobe epilepsy patients was presented to elicit activation in the inferior temporal lobe (as well as other brain regions). Notably, this work allowed us to examine the differing effects that the contrast and signal recovery mechanisms have on fMRI activation in both SFG and non-SFG regions.
1109. Time Resolved FMRI: 100 Ms Resolution in Time for Extended Network Analysis of the Human Brain
Julia Reinhardt1,2, Ernst Nennig3, Stephan Walther4, Sabine Heiland2, Christoph Stippich1,2
1Department of Neuroradiology, University of Basel Hospital, Basel, Switzerland; 2Division of Neuroradiology, Department of Neurology, University of Heidelberg, Medical Center, Heidelberg, Germany; 3OptiMed Medizinische Instrumente GmbH, Ettlingen, Germany; 4Center for Psychosocial Medicine, General Psychiatry, University of Heidelberg, Medical Center, Heidelberg, Germany
Until now the temporal resolution in fMRI was mostly restricted by the used TR. Employing a new method to enhance the time resolution in fMRI below 100 ms we are able to trace neuronal network pathways with extremely short reaction times. The temporal dynamics of somatosensory processing could be measured and correspond with the known values from electrophysiological measures. With this new approach BOLD-fMRI enables to study the temporal dynamics of cortical processing with a temporal resolution of 10 ms.
1110. Evaluating Feraheme as a Potential Contrast Agent for Clinical IRON FMRI
Joseph B. Mandeville1, Krishna Srihasam2, Wim Vanduffel1, Margaret S. Livingstone2
1Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States; 2Department of Neurobiology, Harvard Medical School, Boston, MA, United States
Feraheme is a newly FDA-approved drug for treating chronic iron anemia in clinical populations. The approved iron dose of 510 mg falls within a weight-normalized range of 5-10 mg/kg for human subjects within the range 50-100 kg. To evaluate this drug as a potential contrast-enhancing agent for human clinical fMRI, we performed experiments in awake non-human primates at 3 Tesla to validate theoretical calculations. Results suggest that this agent could enhance the CNR ratio of clinical fMRI by factors of 5 and 2.5 and 1.5 at 3 Tesla, respectively.
1111. Reproducibility of T1 and Tissue Fractional Volume Mapping Using FRASIER: An Application to FMRI Settings
Wanyong Shin1, Hong Gu1, Yihong Yang1
1Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, United States
Recently, FRActional Signal mapping from InvErsion Recovery (FRASIER) was proposed to map T1 and tissue fractional volume in the brain. In this study we incorporated FRASIER into an fMRI protocol and assessed the reproducibility of the technique. Using FRASIER, 15 slice T1 and fractional volume maps were acquired in every 10 seconds with 64¡¿64 matirx size. Standard deviations of the T1 and fractional volume maps was within 37ms and 3.5% in this study, demonstrating feasibility of FRASIER in fMRI settings.
1112. Functional MRI on an Open 1.0 T MRI Scanner: A Comparison with a State-Of-The-Art 3.0 T MRI Scanner
Elsmarieke van de Giessen1, Paul F.C. Groot2, Jan Booij1, Wim van den Brink3, Dick J. Veltman3, Aart J. Nederveen2
1Nuclear Medicine, Academic Medical Center, Amsterdam, Netherlands; 2Radiology, Academic Medical Center, Amsterdam, Netherlands; 3Amsterdam Institute for Addiction Research, Academic Medical Center, Amsterdam, Netherlands
This study is the first, to our knowledge, that tests the feasibility of fMRI on an open MRI system, with a magnetic field strength of 1.0 T, and compares the results with fMRI on a state-of-the-art 3.0 T MRI scanner. The optimal echo time for fMRI on an open 1.0 T MRI system was found to be around 70 ms. Results show that fMRI on an open 1.0 T MRI scanner is feasible for studies that are designed to analyze data at a group level, though not optimal for studies on single subjects.
1113. An EEG Homologue of the Negative BOLD Response as Measured at 7 Tesla
Wietske van der Zwaag1,2, Marzia De Lucia3, Nadine Graedel2, Micah M. Murray3, Rolf Gruetter1,2
1Radiologie, Université de Lausanne, Lausanne, Vaud, Switzerland; 2CIBM, EPFL, Lausanne, Vaud, Switzerland; 3Electroencephalography Brain Mapping core, CHUV, Lausanne, Vaud, Switzerland
The basis of fMRI experiments is a tight coupling of neural activity with the BOLD response in both space and time. However, cross-modal negative BOLD signal may also be caused by blood-steal effects. Here, we measure the negative BOLD signal using ultra-high field fMRI and the neuroelectrical activity as measured by EEG in the same subjects. Neural deactivation is found in the EEG-based electrical neuroimaging maps in regions partially overlapping with those where the negative BOLD signal is found, implying a possible neural basis for the negative BOLD response.
1114. Substantial Flow-Related Contribution in FMRI Signal Observed in Human Visual Cortex at 4T
Xiao Wang1, Wei Chen1
1Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States
It is a common practice to apply a short repetition time (TR) for acquiring more fMRI volumes within a given total imaging time, thus gaining contrast-to-noise ratio (CNR). However, both the task-evoked BOLD (T2/T2*) effect and flow-related component (R1) increases could contribute to the total percentage change of fMRI signal. This study aims to quantitatively evaluate the BOLD and flow contributions in the fMRI signal detected by gradient echo EPI in the human visual cortex during visual stimulation at 4T. The results show a substantially large flow-related contribution in the measured fMRI signal when TR is short. The observed flow-related enhancement in fMRI signal is likely attributed by perfusion change, and it benefits fMRI mapping in two aspects: improved CNR and specificity. The finding also suggests that the flow-related component needs to be considered in BOLD quantification (e.g., calibration of CMRO2).
1115. Compromised Temporal Responsivity in Fusiform Areas by Aging
Makoto Miyakoshi1, Annabel Shen-Hsing Chen2, Kayako Matsuo3, Toshiharu Nakai
1National Center for Geriatrics and Gerontology, Ohbu, Aichi, Japan; 2Nangyang Technorogical University; 3National Taiwan Univsersity
To study the aging effect on neural mechanism of visual repetition, we performed an fMRI study. Participants saw inside and outside scenes repeatedly for five blocks, and the first two blocks (eight repetitions for each scene) were compared with the last two blocks for Young and Elderly groups. The results showed that the Elderly group has longer time-constant for the visual repetition effect to take place within fusiform areas and the occipital cortex. The results supported the conclusion that the aging effect on visual repetition is represented by the compromised ‘slew rate’ i.e., temporal responsivity in the fusiform gyri.
1116. Hemodynamic Response Function (HRF) Modulation by Inhaled CO2 Concentration Using Event-Related FMRI
Chao-Chun Lin1,2, Yi-Jui Liu3,4, Chien-Kuo Chen3, Hsiao-Wei Peng3, Kuo-Fang Shao4, Wu-Chung Shen1,5, Chang Hing-Chiu6
1Department of Radiology, China Medical University Hospital, Taichung, Taiwan, Taiwan; 2Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, Taiwan; 3Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan; 4Master's Program in Biomedical Informatics and Biomedical Engineering, Feng Chia University, Taichun, Taiwan; 5School of Medicine, China Medical University, Taichung, Taiwan; 6Applied Science Laboratory, GE Healthcare Taiwan, Taipei, Taiwan
The purpose of this study was to evaluate the hemodynamic response function (HRF) change after inhalation of different carbon dioxide concentrations. Using event-related method investigate the transient hemodynamic response function by short-time visual stimulus with different CO2 concentrations. Our results show that the peak of HRF curve is decreased and delayed with increased inhaled CO2 concentrations, and the width of HRF curve is wider with higher inhaled CO2 concentration.
1117. Increased Metabolic Activity, Not Preemptive Blood Flow Increase, Underlies Attentional Modulation in Primary Visual Cortex
Farshad Moradi1, Richard Buxton1
1Radiology, University of California, San Diego, San Diego, CA, United States
Previous studies found that attention produces robust BOLD modulation with only modest increase in firing activity in primary visual cortex. This could be due to a pure preemptive CBF increase with no relation to local neuronal firing. We tested the presence of such a mechanism using combined CBF/BOLD measurements to estimate relative CMRO2. Results show that attentional enhancement of V1 activity involves an increase of both metabolic activity and blood flow, rather than a preemptive increase in blood flow alone. The ratio of CBF to CMRO2 change appears to be higher when the stimulus is unattended than when attended.
1118. Uncoupled Couplings: Combined FMRI and 1H-MRS for the Study of the Neurovascular and Neurometabolic Coupling
Mauro DiNuzzo1, Federico Giove1,2, Bruno Maraviglia1,2
1Physics, Sapienza University of Rome, Rome, RM, Italy; 2MARBILab, "Enrico Fermi" Center, Rome, Italy
Functional magnetic resonance imaging (fMRI) is widely used to map brain function. Nevertheless, it does measure neural activity only indirectly via hemodynamic changes. Here we performed fMRI in combination with 1H-MRS in order to study the relationships between the vascular and metabolic response of the brain to a visual stimulation paradigm specifically designed to partly disentangle spiking and synaptic activity within the primary visual cortex. Our results, though preliminary, confirm that the energetics of the stimulated brain contains more information than that revealed by fMRI alone, thereby indicating an uncoupling between hemodynamics and metabolism upon brain activation.
1119. Decrease of Deoxy-Hemoglobin Containing Blood Volume in Activated Human Visual Cortex
Xiang He1, Dmitriy A. Yablonskiy1
1Mallinckrodt Institute of Radiology, Washington University in St Louis, School of Medicine, St. Louis, MO, United States
Quantification of brain hemodynamic parameters during functional activation is essential for understanding biophysical mechanisms behind blood oxygenation level depend (BOLD) phenomenon. Models of BOLD signal are often derived based on a relationship established by PET studies between cerebral blood volume (CBV) and cerebral blood flow (CBF), ignoring that only portion of CBV - deoxyhemoglobin-containing blood volume (DBV) affects BOLD signal. In this study, we directly measure DBV during visual activation in human visual cortex area using qBOLD-fMRI technique. We demonstrate for the first time that DBV decreases during functional activation – an effect opposite to well known increase in CBV.
R.Allen Waggoner1, Keiji Tanaka1, Kang Cheng1,2
1Laboratory for Cognitive Brain Mapping, RIKEN-BSI, Wako-shi, Saitama, Japan; 2fMRI Support Unit, RIKEN-BSI, Wako-shi, Saitama, Japan
Recent DfMRI studies preformed at 3T have observed an increase in the fractional BOLD signal change with increasing b value during functional stimulation. The origin of this effect remains controversial with both cell swelling and vascular sources being offered as explanations. If this effect is truly due to cell swelling, increasing the static magnetic field will not alter the effect. We present DfMRI results obtained at 4T which shows a constant BOLD signal change with increasing b value. This result is consistent with a vascular source for a varying DfMRI response with diffusion weighting seen at 3T.
1121. Modeling The Non-Neuronal Contribution To The Blood Oxygenation Level Dependent Fmri Signal Oscillations
Mauro DiNuzzo1, Federico Giove1,2, Bruno Maraviglia1,2
1Physics, Sapienza University of Rome, Rome, RM, Italy; 2MARBILab, "Enrico Fermi" Center, Rome, RM, Italy
Resting oscillatory patterns in cortical activity can originate by both network- and metabolism-related mechanisms. In particular, recent evidences suggest that the cell metabolic state exert an indirect control over the intrinsic network responsivity of the brain, much likely via astrocytic intracellular calcium (Ca2+)-mediated gliotransmission. Here we examined theoretically the contribution of astrocytes in the generation of the fMRI signal changes in the absence of focal neuronal stimulations. We found that oscillations in brain electrical, metabolic and vascular activity, as revealed by BOLD fMRI, can be qualitatively and quantitatively explained by calcium-mediated coupling between neuroglial activation and metabolism.
1122. Diffusion Parameter Changes in White Matter Induced by Direct Intracortical Stimulation in Rats
Umesh Suryanarayana Rudrapatna1, Maurits P. van Meer1, Annette van der Toorn1, Rick M. Dijkhuizen1
1Image Sciences Institute, University Medical Center, Utrecht, Netherlands
While existing functional MRI techniques can reliably detect stimulus-induced activation in gray matter, activity in white matter regions has not been readily measured. A recent study has reported subtle increases
in fractional anisotropy (FA) in specific white matter pathways in response to motor or visual stimulation in human subjects. In the current study, we aimed to validate these findings with a direct cortical stimulation paradigm in rats. Our functional DTI approach revealed significant but variable FA changes in restricted corpus callosum regions, which demonstrates that functional DTI enables detection of white matter activity in response to cortical stimulation.
1123. Whole-Brain Mapping of Venous Vessel Size in Humans Using the Hypercapnia-Induced BOLD Effect
Thies Halvor Jochimsen1,2, Dimo Ivanov2, Derek V M Ott2, Wolfgang Heinke3, Robert Turner2, Harald E. Möller2, Jürgen R. Reichenbach1
1Medical Physics Group, Department of Diagnostic and Interventional Radiology, Jena University Hospital, Jena, Germany; 2Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 3Department of Anesthesiology and Intensive Care Medicine, University of Leipzig, Medical Faculty, Leipzig, Germany
It is demonstrated that non-invasive mapping of the venous microstructure (vessel radius) is possible by using the hypercapnia-induced BOLD effect. Furthermore, it is shown that maps of venous blood volume and vessel density can be obtained from the same experimental setup. These parameters are important for characterizing tumor angiogenesis and type.
Jeroen Cornelis Siero1, Natalia Petridou2,3, Johannes Marinus Hoogduin2, Nick F. Ramsey1
1Rudolf Magnus Institute, University Medical Center Utrecht, Utrecht, Netherlands; 2Radiology, University Medical Center Utrecht, Utrecht, Netherlands; 3SPMMRC, University of Nottingam, Nottingam, United Kingdom
A limitation of T2*w BOLD fMRI is the confounding contribution of signal from the larger vasculature. Based on time-to-peak and full-width-at-half-maximum BOLD characteristics of different vascular compartments identified at 3T, we characterized the spatio-temporal properties of the BOLD response at 7T in the visual cortex using an event-related fMRI paradigm with short visual stimuli, high sampling rate, and multiple spatial resolutions. For the smallest voxelsize a high time-to-peak spatial heterogeneity of the BOLD response was observed with fast responses localized in parenchyma. This opens the possibility to use TTP to probe layer specific BOLD responses in the human brain.
1125. Linearity of Neural Responses in the Somatosensory Cortex and Their Relationship to BOLD FMRI.
Fan Wang1, Claire Stevenson1, Matthew Brookes1, Peter Morris1
1Physics, Sir Peter Mansfield Magnetic Resonance Centre, Nottingham, Nottinghamshire, United Kingdom
We use the combination of MEG and fMRI to study the neural basis for BOLD non-linearity. Both nonlinear neural responses to stimuli and nonlinear vascular responses to neural activity may contribute to BOLD non-linearity and the relative contribution of these two effects remains poorly understood. We extended the study of non-linear neural response to both phase locked evoked response and time related beta oscillations in somatosensory cortex. The N20 peak amplitudes show non-linearities with ISI of 0.25-2s, influenced by beta power at the time of stimulation, suggesting that best oscillation should also be considered for BOLD convolution.
1126. Simultaneous BOLD and NIRS Signal Correlation During Hypoxia
Matthew Borzage1,2, Marvin Nelson3, Istvan Seri1,4, Stefan Blüml3,5
1Neonatal Medicine, Childrens Hospital Los Angeles, Los Angeles, CA, United States; 2Viterbi School of Engineering, University of Southern California, Los Angeles, 90007, United States; 3Department of Radiology, Childrens Hospital Los Angeles, Los Angeles, CA, United States; 4Keck School of Medicine, University of Southern California, Los Angeles, CA, United States; 5Rudi Schulte Research Institute, Santa Barbara, CA, United States
Studying changes in cerebral hemodynamics is possible via MR, including blood oxygen level dependent (BOLD) imaging. We used near infrared spectroscopy (NIRS) to sample oxy- and deoxyhemoglobin directly, and utilized a nitrogen challenge to change FiO2 and thus cause measurable changes in blood oxygenation. We have observed good correlation between the BOLD and NIRS signals, with higher correlation in the gray matter than in the white matter. In the near future, we will use this paradigm to study the limited autoregulation of cerebral blood flow in preterm neonates.
1127. Cerebral Blood Volume Changes in Arterial and Post-Arterial Compartments and Their Relationship with Cerebral Blood Flow Alteration During Brief Breath-Holding and Visual Stimulation in Human Brain
Jun Hua1, Robert Stevens1, Manus J. Donahue1,2, Alan J. Huang1, James J. Pekar1, Peter C.M. van Zijl1
1Department of Radiology, The Johns Hopkins University, Baltimore, MD, United States; 2Department of Clinical Neurology, Oxford University, Oxford, United Kingdom
Changes in CBF/CBV/arterial-CBV(CBVa)/post-arterial-CBV(CBVpa) were measured in human brain during breath-hold and visual stimulation. δCBV/CBV was larger during breath-hold (54.9+/-5.8%) than visual stimulation (28.2+/-5.2%), a difference primarily originating from δCBVpa/CBVpa (54.5+/-4.9% vs. 22.2+/-3.8%); δCBVa/CBVa (53+/-6%) and δCBF/CBF (61+/-7%) were comparable in both tasks. During breath-hold, vasodilation distributed proportionally among arterial and post-arterial compartments, whereas, during visual stimulation, relative change in CBVa was greater than that in CBVpa. Our data indicate that the coupling between arterial-CBV and CBF was largely preserved during both tasks (rCBVa=rCBF0.86+/-0.05), while the relationship between total-CBV and CBF was substantially different between breath-hold (rCBV=rCBF0.90+/-0.05) and visual (rCBV=rCBF0.52+/-0.04) stimulation.
Daniel Pflugfelder1, Kaveh Vahedipour1, Kamil Uludag2, Nadim Jon Shah1,3, Tony Stöcker1
1Institute of Neuroscience and Medicine 4, Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany; 2Max-Planck Institute for Biological Cybernetics, Tuebingen, Germany; 3Faculty of Medicine, Department of Neurology, RWTH Aachen University, Aachen, Germany
To increase the spatial specificity of the BOLD signal, a large ratio R of microvascular to macrovascular BOLD signal is desirable. This can be be achieved using spin echo sequences. To simplify the calculation the extravascular BOLD signal (EV) is often approximated by a mono-exponential decay (MEA). To investigate the effect of the MEA we calculated R for multiple B0 and TE without using this approximation. The parameter range for an optimal R was considerable different to the results obtained using the MEA. This is mainly due to an vessel radius dependent delay of the EV which is not reproduced by the MEA.
1129. A Realistic Vascular Model for BOLD Signal Up to 16.4 T.
Bernd Michael Müller-Bierl1, Verena Pawlak2, Jason Kerr2, Kamil Ugurbil3, Kamil Uludag1
1MRC, Max-Planck Institute for Biological Cybernetics, Tübingen, Germany; 2NWG, Max-Planck Institute for Biological Cybernetics, Tübingen, Germany; 3Center for Magnetic Resonance Research, University of Minnesota, Minnesota, Minneapolis, United States
We present a realistic vascular model based on Monte-Carlo modeling of diffusion and the finite element method to compute the background magnetic field of partly oxygenated finite venules exposed to up to 16.4 T. Our data show that the realistic vasculature data set is necessary to account for the effects due to finite-sized vessels. The venule data herein stems from 2 photon microscopy of the rat brain. Results show that the infinite vessel model is prone to error so that the use of realistic vascular data sets is necessary to get precise results. However, for a better understanding more realistic vascular data sets should be examined in future work.
1130. Relaxation of Blood at High Field: Another Exchange Regime
Ksenija Grgac1,2, Qin Qin1,3, Michael McMahon1,3, Jason Zhao1, Peter C.M. van Zijl1,3
1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States; 2Department of Chemistry, Johns Hopkins University, Baltimore, MD, United States; 3F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States
To study the intravascular BOLD mechanism, we used a physiologically controlled blood perfusion system at 9.4T under oxygenated conditions for a series of hematocrits. Previous studies have shown that, at such high fields, the two-site (eryhtrocyte-plasma) fast exchange model can not describe oxygenation-based relaxation changes properly in that it gives incorrect lifetimes for water in erythrocytes (1-3ms). We show that, for the physiological range of hematocrits, a general two-site exchange model (including slow, fast and intermediate regimes) can appropriately describe blood relaxation in oxygenated blood and provides an erythrocyte lifetime of 12.2±3.7ms, in agreement with literature values
1131. Blood Longitudinal (T1) and Transverse (T2) Relaxation Times at 11.7 Tesla
Ai-Ling Lin1, Xia Zhao1, Peter T. Fox1, Timothy Q. Duong1
1Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, United States
Knowledge of blood T1 and T2 values are important for many MRI studies that include BOLD modeling, high spatial specificity BOLD fMRI, blood flow MRI using arterial spin labeling (ASL), and blood volume MRI using vascular space occupancy (VASO) techniques. The purpose of the present study was to determine blood T1 and T2 values at 11.7T as a function of oxygenation level (Y), temperature, hematocrit fraction (Hct) and field strength (B0).
Xiaopeng Zong1, Jie Huang1,2
1Department of Radiology, Michigan State University, East Lansing, MI, United States; 2Neuroscience Program, Michigan State University, East Lansing, MI, United States
A quantitative ER-fMRI study requires to measuring hemodynamic response function (HRF) both accurately and precisely. A periodic ER-fMRI design can produce a high accuracy of HRF measurement but a low precision. Utilizing the approximate linearity of the HRF, a rapid-presentation (RP) ER-fMRI design can improve the precision by shorting intersitimulus interval (ISI). Nevertheless, hemodynamic response is non-linear and its corresponding effect on the estimated HRF increases with decreasing ISI, rendering the estimated HRF inaccurate for small ISI values. Accordingly, as demonstrated in this preliminary study, an optimal RP ER-fMRI design should maximize both accuracy and precision of HRF measurements.
1133. Saturation of Visually Evoked BOLD Response During Carbogen Inhalation
Claudine J. Gauthier1,2, Cécile Madjar2, Richard D. Hoge1,2
1Physiology/Biomedical Engineering, Université de Montréal, Montréal, Quebec, Canada; 2CRIUGM, Montreal, Quebec, Canada
Oxidative metabolism can be estimated from the BOLD signal following a calibration manipulation to determine a factor M. M is the maximum possible BOLD signal change. Carbogen inhalation was used here with intense visual stimulation to test whether an asymptote in BOLD signal could be reached. Results show a convergence of percent BOLD changes around 9% in visual cortex for 10% carbogen alone, and 5-10% carbogen breathing plus visual stimulation. The diminishing incremental response from visual stimulation at high carbogen concentrations suggests that these manipulations approach BOLD levels close to the saturation plateau.
1134. Calibrated FMRI During a Cognitive Stroop Task in the Aging Brain
Rafat Saeed Mohtasib1,2, Vanessa Sluming1,2, Laura Parkes1,3
1Magnetic Resonance and Image Analysis Research Centre (MARIARC), The University of Liverpool, Liverpool, United Kingdom; 2Medical Imaging Department, The University of Liverpool, United Kingdom; 3Imaging Science and Biomedical Engineering, School of Cancer and Imaging Sciences, The University of Manchester, United Kingdom
Calibrated fMRI is a new technique that allows quantitative estimates of the relative changes in cerebral metabolic rate of oxygen (ÄCMRO2) and cerebral blood flow (ÄCBF) that accompany neural activation. In this research we extend our previous work to study changes in neurovascular coupling over an age range during a cognitive Stroop task.
37 volunteers (age range 20-70) were scanned using 3T MRI. We found BOLD response to the Stroop task increases with increasing age, calibration constant A was found to reduce with age, a trend to reduced ÄCMRO2 with increasing age, and globally ÄCBF did not change with age.
1135. Error Propagation in CMRO2 Derivations Using CBF and BOLD Imaging
Hsiao-Wen Chung1, Wen Chau Wu
1Electrical Engineering, National Taiwan University, Taipei, Taiwan, Taiwan
The purpose of this study is therefore to investigate the issues error propagation in CMRO2 estimations under different CNR. Results from our error propagation study suggest that CMRO2 estimations using CBF and BOLD are valid only when the CNR for CBF measurements is sufficiently large, or when the underlying changes in CMRO2 and CBF are sufficiently large as in hypercapnic experiments. Validity of current instantaneous CMRO2 measurements for resting-state brain functional studies is therefore in some doubt.
1136. Effects of the ValSalva Maneuver and Hypercapnia on the BOLD Signal
Daniel A. Handwerker1, Paula Wu1,2, Ronald M. Harper3, Peter A. Bandettini1,4
1Section on Functional Imaging Methods, National Institute of Mental Health, Bethesda, MD, United States; 2Neuroscience, University of California, Los Angeles, Los Angeles, CA, United States; 3Neurobiology, David Geffen School of Medicine, UCLA, Los Angeles, CA, United States; 4Functional MRI Facility, National Institute of Mental Health, Bethesda, MD, United States
Hypercapnia creates global changes in cerebral blood flow, volume, and oxygenation that can be measured with fMRI and used for calibration. Breath-holding is a simple way to induce hypercapnia, but it may alter thoracic chest pressure and include a ValSalva effect. We alter chest pressure while keeping the hold duration constant to see how the BOLD signal changes. The initial BOLD undershoot and following peak scale with pressure. Because the precise contrast mechanisms behind these changes are not fully understood, they may be a confound in calibration studies, or a novel way to rapidly induce calibration-useful global BOLD signal changes.
1137. Hypoxia and Hyperoxia Alter Brain Metabolism in Awake Human
Feng Xu1, Uma Yezhuvath1, Peiying Wang1, Hanzhang Lu1
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States
Many studies tried to understand how neural activity change vascular parameters, but little attention was received to whether gas content changes in blood would reversely alter neural activity. To investigate such an effect, we used a recently developed MRI technique to quantify global cerebral metabolic rate of oxygen (CMRO2) under hypoxia and hyperoxia. Our data suggest that a change in arterial oxygen content can modulate brain metabolism in a dose-dependent manner, with hypoxia increasing CMRO2 and hyperoxia decreasing it. Therefore, in addition to the well-known “forward” neurovascular coupling, the “reverse” coupling may be important in the regulation of brain function.
Clarisse Ildiko Mark1, M. Slessarev2, S. Ito3, J. Han2, J. A. Fisher2, G. B. Pike1
1McConnell Brain Imaging Center, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; 2Department of Anaesthesiology, University Health Network, Univeristy of Toronto,, Toronto, Ontario, Canada; 3Department of Anaesthesiology and Medical Crisis Management, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
Manual HC calibration depends on intrinsically low signal-to-noise perfusion imaging and individual vascular architecture, with resulting calibration (M)-values prone to large intra- and inter-subject variations that may bias oxygen metabolism studies. We thereby sough to investigate HO as a calibration alternative under rigorous control of end-tidal partial pressures of CO2 (PetCO2) and O2 (PetO2). Our findings suggest the viability of precisely controlling HO stimulation to provide more precise per-subject and per-brain-region M-estimates, based on high SNR PaO2 measurements and the removal of the confound of vascular variation in population observed under HC-calibration.
1Otorhinolaryngology, University Medical Center Groningen, Groningen, Netherlands; 2Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA, United States
Spatial Independent Component Analysis (sICA) is increasingly being used for the analysis of fMRI datasets with unpredictable response dynamics, like in resting state experiments. However, group-level statistical assessments are difficult, and proper statistical characterization and validation under the null-hypothesis are so far lacking. In the current study, a novel method is proposed that is based on retrospective matching of individual component maps to aggregate group maps. Selection bias is analytically predicted and explicitly corrected for. It is shown that valid outcomes are obtained, in the sense that the achieved specificity does not violate the imposed confidence levels, only if bias-correction is applied. Sensitivity and discriminatory power remain acceptable, and only moderately smaller than those of a biased method. Finally, it is shown that the method is able to identify significant effects of interest in an actual dataset, proving its applicability as a group-level sICA fMRI data analysis method.
1140. Eigenvector Centrality Mapping as a New Model-Free Method for Analyzing FMRI Data
Gabriele Lohmann1, Daniel S. Margulies1, Dirk Goldhahn1, Annette Horstmann1, Burkhard Pleger1, Joeran Lepsien1, Arno Villringer1, Robert Turner1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
We introduce a new assumption- and parameter-free method for the analysis of fMRI resting state data based on „eigenvector centrality”. Eigenvector centrality attributes a value to each voxel in the brain such that a voxel receives a large value if it is strongly correlated with many other nodes that are themselves central within the network. Google's PageRank algorithm is a variant of eigenvector centrality. We tested eigenvector centrality mapping (ECM) on two resting state scans of 35 subjects, and found a network of hubs including precuneus, thalamus and sensorimotor areas of the marginal ramus of the cingulate and mid-cingulate cortex.
1141. ROI Atlas Generated from Whole Brain Parcellation of Resting State FMRI Data
Richard Cameron Craddock1,2, George Andrew James3, Paul Edgar Holtzheimer2, Xiaoping P. Hu3, Helen S. Mayberg2
1Electrical and Computer Engineering, Georiga Institute of Technology, Atlanta, GA, United States; 2Psychiatry, Emory University, Atlanta, GA, United States; 3Biomedical Imaging Technology Center, Emory University/Georgia Institute of Technology, Atlanta, GA, United States
Network analysis of resting state fMRI data requires the specification of ROIs. This is a difficult process fraught with error. We propose a method for developing an ROI atlas by whole brain parcellation of resting state data in functinally homogenous, contiguous regions.
1142. fMRI Topographic Mapping of the Somatosensory Cortex at 7T Using Multigrid Priors
Selene da Rocha Amaral1, Sue Francis1, Penny Gowland1, Nestor Caticha2
1Sir Peter Mansfield Magnetic Centre, University of Nottingham, Nottingham, Notts, United Kingdom; 2Institute of Physics, University of Sao Paulo, Sao Paulo, Brazil
We have applied a Bayesian non-parametric multiscale technique, the iterated Multigrid Priors method, to map the digits of the hand in primary somatosensory cortex for 1mm isotropic spatial resolution data. It is data driven and makes no assumption about the local hemodynamic response as a function of time or space. It was able to detect an orderly pattern of response phases on the posterior bank of the central sulcus (postcentral gyrus) suggesting that the method can also be extended for retinotopic mapping studies of visual cortex. We also showed variations in HRs across digits through local posterior spatial averages.
1143. Support Vector Regression Prediction of Graded FMRI Activity
Yash Shailesh Shah1, Douglas C. Noll, Scott J. Peltier
1Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
Support Vector Regression is a machine learning technique that learns the mapping from the training set and labels provided. This creates a model which can then be used to give predictions for all testing sets. The prediction is really quick and hence SVR has potential to be used as a tool for real-time biofeedback applications to evaluate graded potential. In this study, we have used SVR analysis to evaluate graded activation in multiple neural systems namely the visual and motor cortex activation. The outputs are encouraging and advocate prospects of using SVR for future work in building real-time biofeedback applications in which graded activation needs to be evaluated.
1144. A Comparison of SVM and RVM for Real-Time FMRI Applications
Daniel Antonio Perez1, Richard Cameron Craddock2, George Andrew James1, Xiaoping Philip Hu1
1The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA, United States; 2School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta,, GA, United States
Support vector machines (SVM) and relevance vector machines (RVM) are two machine learning algorithms which have gained popularity due to its sensitivity to networks of brain activation. Despite their recent extensive use in fMRI research, little contribution has been put forth to compare these different algorithms. Both models were compared for speed and prediction accuracy. The results revealed that both RVM and SVM are comparable in classification accuracy. However, RVM is capable of performing the task much faster and with a sparser model. Feature selection was also found to increase both speed and classification accuracy for both SVM and RVM.
1145. Using Eigenvector Centrality to Measure the Effect of Propofol-Induced Sedation on Functional Connectivity
Gabriele Lohmann1, Wolfgang Heinke2, Burkhard Pleger1, Joeran Lepsien1, Stefan Zysset3, Robert Turner1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 2Dept. of Anesthesiology and Intensive Medicine, University of Leipzig, Leipzig, Germany; 3NordicNeuroLab, Norway
Propofol is an anesthestic agent widely used in clinical practice which is known to affect episodic memory. The exact mechanism causing this effect is still unclear. Here we investigated whether propofol has a region-specific effect on functional connectivity in fMRI data. Subjects were scanned under the influence of propofol or a placebo. Functional connectivity was assessed using an algorithm new to fMRI data analysis called 'eigenvector centrality'. Our results suggest that the well known impairment of episodic memory after propofol infusion is related to an impaired function of cerebellar regions known to be involved in memory encoding.
John McGonigle1, Andrea L. Malizia2, Robin Holmes3, Majid Mirmehdi1
1Computer Science, University of Bristol, Bristol, United Kingdom; 2Psychopharmacology Unit, University of Bristol, Bristol, United Kingdom; 3Medical Physics, United Bristol Healthcare NHS Trust, Bristol, United Kingdom
Data-driven analysis is useful in pharmacological MRI where there may be no model of neural response available a priori. It is recognised that the signal complexity of noise will usually be higher than any signal of interest. Renyi entropy may be used to discover the complexity of a time frequency representation of a voxel time course. Its application here at every voxel in a region of interest across several subjects shows it is capable of discovering drug effect which is not found when the same analysis is carried out on placebo data.
1147. Functional MRI Constrained EEG Sources Localization for Brain State Classification
Changming Wang1,2, Zhihao Li1, Gopikrinsha Desphande1, Li Yao2, Xiaoping Hu1
1Biomedical Engineering, Emory Univ./Georgia Tech., Atlanta, GA, United States; 2Inst. of Cog. Neurosci. & Learning, Beijing Normal Univ., Beijing, China
We used fMRI to assist single-trial EEG signal classification by transforming scalp EEG into corresponding source activation patterns. The classification performance for 4 categories visual perception task was around 98%.
1148. Development of an Automated Threshold Technique Based on Reproducibility of FMRI Activation.
Tynan Stevens1,2, Steven Beyea, 12, Ryan D'Arcy2,3, David Clarke4,5, Chris Bowen, 12, Gerhard Stroink1
1Physics, Dalhousie University, Halifax, NS, Canada; 2NRC Institute for Biodiagnostics (Atlantic), Halifax, NS, Canada; 3Neuroscience, Dalhousie University, Halifax, NS, Canada; 4Neurosurgery, QEII Health Science Center, Halifax, NS, Canada; 5Surgery, Dalhousie University, Halifax, NS, Canada
Setting activation thresholds remains a challenge in functional MRI. While strategies exist to address the increased chance of false positive activations due to the large number of voxels in an fMRI image, these methods frequently ignore differences in activation strength between tasks, individuals, and scanners. Setting appropriate thresholds is particularly pertinent in presurgical mapping, as knowledge of the location and extent of functional cortex can affect surgical decisions. In this work, we demonstrate an automated threshold technique based on test-retest imaging and receiver-operator characteristic curves, which produces individualized threshold levels optimized for reproducibility of the observed activation.
1149. Semiparametric Paradigm Free Mapping: Automatic Detection and Characterization of FMRI BOLD Responses and Physiological Fluctuations Without Prior Information
Cesar Caballero-Gaudes1, Natalia Petridou, 12, Susan Francis1, Penny Gowland1
1Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom; 2University Medical Centre Utrecht, Utrecht, Netherlands
In recent work we showed that by means of sparse estimation techniques the spatial and temporal evolution of single-trial BOLD responses can be automatically detected without any prior knowledge of the stimulus timing and without thresholding: paradigm free mapping (PFM). However, fMRI time series also contain physiological and instrumental fluctuations which can hinder the detection of BOLD responses associated to neuronal activity. Physiological fluctuations can be removed prior to PFM via high-pass filtering, or by RETROICOR, RVT or RVHRCOR, but these techniques must be employed in a pre-processing stage and require the additional recording of physiological respiratory and cardiac waveforms. Here, extending on our previous work, we present a novel technique which by decomposing the fMRI signal enables automatic detection of fMRI BOLD responses without prior stimulus information and automatic fitting of significant frequency fluctuations present in the signal, such as non-neuronal cardiac and respiratory fluctuations (semiparametric PFM, sPFM). This technique is based on a semiparametric linear representation of the fMRI signal which is recursively fitted using a morphological component analysis algorithm. The feasibility of this technique was evaluated in simulations and real fMRI data acquired at 7T, and its performance validated to RETROICOR.
1150. Spatial Registration of Support Vector Machine Models for Multi-Session and Group Real-Time FMRI
Andrew Fischer1, Jonathan Lisinski2, Pearl Chiu2, Brooks King-Casas2, Stephen LaConte2
1Rice University, Houston, TX, United States; 2Neuroscience, Baylor College of Medicine, Houston, TX, United States
A pattern-based rt-fMRI system capable of multi-session and group-based models enables progressive training and testing across sessions, and potentially enables the use of group models for rehabilitation/therapy using multi-voxel targets built from databases of recovered individuals. Here we investigate alignment strategies to verify that there is not a significant tradeoff between classification accuracy and rt-fMRI computational demands. Our results demonstrate the feasibility of a model-to-scan alignment system for real-time fMRI in which the least demanding computational approach does not lead to a compromise of classification accuracy. This work also demonstrates the feasibility of using group SVM models in real-time experiments.
1151. Constrained CCA with Different Novel Linear Constraints and a Nonlinear Constraint in FMRI
Dietmar Cordes1, Rajesh Nandy2, Mingwu Jin1
1Radiology, University of Colorado Denver, Aurora, CO, United States; 2Biostatistics and Psychology, UCLA, Los Angeles, CA, United States
Multivariate statistical analysis has recently become popular in fMRI data analysis as such methods can capture better the spatial dependencies between neighboring voxels. One such method is local canonical correlation analysis (CCA) where one looks at the joint time courses of a group of neighboring voxels. It is known that CCA without any constraints can lead to significant artifacts and an increase in false activations. Here, we investigate different novel linear constraints and a nonlinear constraint for CCA and propose a method that rectifies the weakness of conventional CCA mentioned above.
1152. An Optimized Clustering Technique for Functional Parcellation of Hippocampus
Arabinda Mishra1, James C. Gatenby1, Allen T. Newton1, John C. Gore1, Baxter P. Rogers1
1Radiology & Radiological Science, VUIIS, Nashville, TN, United States
Functional sub-divisions of important anatomic regions in the human brain are normally done based on disparities in structural connectivity patterns or functional connectivity maps. However, quantification of functional heterogeneity, and determining the appropriate number of sub-regions, has rarely been a focus of study. This work evaluates the use of self organized maps (SOM) to classify the functionally different regions in the hippocampus, which exhibits functional and sometimes anatomical differences in patients with disorders such as schizophrenia and bipolar disorder etc. Using voxel based connectivity maps we successfully parcellated left hippocampus and found performance of SOM to be superior in comparison to kmeans clustering.
1153. Spatiotemporal Dynamics of Low Frequency Fluctuations in BOLD FMRI of Rats and Humans
Waqas Majeed1, Matthew Magnuson1, Shella Keilholz1
1Biomedical Engineering, Georgia Institute of Technology / Emory University, Atlanta, GA, United States
Presence of propagating spatiotemporal waves in low frequency fluctuations (LFFs) has recently reported using high temporal resolution single slice BOLD fMRI of the rat brain. We have developed a novel method for automatic detection of such patterns and some initial findings for multslice rat and human data are presented in this abstract.
1154. A Statistical Method for Computing BOLD Activations in Multi-Echo Time FMRI Data Sets and Identifying Likely Non-BOLD Task Related Signal Change
Andrew Scott Nencka1, Daniel L. Shefchik1, James S. Hyde1, Andrzej Jesmanowicz1, Daniel B. Rowe2
1Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States; 2Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI, United States
The T2* contrast mechanism associated with the BOLD signal is well known, as is its echo time (TE) dependence. In this abstract, we present a method for analyzing data acquired with interleaved echo times. Based upon the expected BOLD TE behavior, the ratio of the regression coefficients for the task related columns of the design matrix may be used to identify voxels which exhibit BOLD-like responses.
1155. Eigenspace Minimum L1-Norm Beamformer Reconstruction of Functional Magnetic Resonance Inverse Imaging of Visuomotor Processing
Shr-Tai Liou1, Hsiao-Wen Chung1, Wei-Tang Chang2, Fa-Hsuan Lin2,3
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan; 2Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan; 3A. A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, United States
We propose the eigenspace L1-norm beamformer, a new novel technique for ultrafast MR inverse imaging (InI) reconstruction. This method minimizes the amplitude of the beamformer output quantified by the L1-norm of the spatial filter coefficients. We tested this method to reconstruct functional MR InI measurements using a visuomotor task. Results show that the eigenspace L1-norm beamformer can detect BOLD contrast functional activity and provide higher spatial resolution than linear constrained minimum variance (LCMV) beamformer in both motor and visual cortices.
1156. Filtering FMRI Using a SOCK
Kaushik Bhaganagarapu1,2, Graeme D. Jackson1,3, David F. Abbott1,2
1Brain Research Institute, Florey Neuroscience Institutes (Austin), Melbourne, Victoria, Australia; 2Department of Medicine, The University of Melbourne, Melbourne, Victoria, Australia; 3Departments of Medicine and Radiology, The University of Melbourne, Melbourne, Victoria, Australia
BOLD fMRI is restricted by low signal to noise and various artifacts varying from motion to physiological noise. Independent components analysis (ICA) is a data-driven analysis approach that is being used to filter fMRI of such noise. However, one of the problems with ICA remains the interpretation of the results. Recently, we developed an automatic classifier (Spatially Organised Component Klassifikator - SOCK), which uses spatial criteria to help distinguish plausible biological phenomena from noise. We utilize SOCK to automatically filter a conventional fMRI block-design language study and successfully show the significance of activation obtained increases as a result of SOCK.
1157. Real Time FRMI: Machine Learning or ROIs?
Thomas WJ Ash1, T Adrian Carpenter1, Guy B. Williams1
1Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom
The first applications of real time fMRI used voxel intensity averaging over a ROI to provide feedback, whereas recent work has shown that machine learning tools may improve performance. We conduct a comparison between the two techniques, and find that support vector machines (SVM) outperform averaging over a ROI no matter how restricted an ROI we use. Further to this, we find that SVM performance does not decrease as sharply as ROI averaging when block length is decreased.
1158. Using Dynamically Adaptive Imaging with FMRI to Rapidly Characterize Neural Representations
Rhodri Cusack1, Michele Veldsman1, Lorina Naci2, Daniel Mitchell1
1MRC CBU, Cambridge, Cambs, United Kingdom; 2University of Cambridge, Cambridge, United Kingdom
Dynamically Adaptive Imaging (DAI) is a new real-time paradigm for fMRI. BOLD data were analyzed using our open-source real-time software and used to iteratively and automatically adapt the stimuli presented to the volunteer. DAI was applied to investigate feature coding in ventral visual cortex. Pictures of objects were presented on a screen. We performed an iterative search, in which the outcome of the experiment was the neural neighborhood of stimuli that evoked the most similar pattern of neural response to a referent stimulus. DAI converged rapidly and found object-specific tuning to complex conjunctions of sensory and semantic features.
1159. A Novel Artifact Reduction Strategy for Retaining and Detecting Changes in Muscle Activity in the MR Environment
Jaimie B. Dougherty1, Christopher J. Conklin2, Karen Moxon1, Scott Faro2, Feroze Mohamed2
1Drexel Univesrity, Philadelphia, Pa, United States; 2Temple University, Philadelphia, Pa
Combined EMG and fMRI is very desirable. Detecting changes in muscle activity associated with changes in cortical activity can greatly improve our understanding of neuroplastic changes and the affects of treatments in neuromuscular conditions. This work proposes a robust wavelet-based artifact reduction strategy that allows for the distinction between two muscular conditions in an MR environment. This work also introduces the use of the EMG parameter median frequency as a covariate in a motor fatigue study to better refine image analysis.
Ali Mohammad Golestani1, Bradley G. Goodyear2,3
1Electrical & Computer Engineering, University of Calgary, Calgary, AB, Canada; 2Radiology & Clinical Neuroscience, University of Calgary, Calgary, AB, Canada; 3Seaman Family MR Research Centre, Calgary, AB, Canada
Resting-state fMRI analysis techniques that determine the similarity between time varying signals of seed and target regions assume the signals are stationary; however, the resting-state varies between subjects and is susceptible to unwanted brain activity due to inadvertent movements or cognition. In this study, we introduce a time-frequency approach based on the Stockwell transform to temporally resolve coherence between resting-state signals. We demonstrate S-Coherence can reduce the contribution of unwanted hand movements in the determination of the resting-state connectivity within the motor network, and hence reduce within-subject variability in comparison with existing techniques (temporal cross-correlation and coherence).
1161. A Novel Data Processing Method for Olfactory FMRI Examinations
Xiaoyu Sun1, Jianli Wang1, Christopher W. Weitekamp1, Qing X. Yang1,2
1Radiology, Penn State University College of Medcine, Hershey, PA, United States; 2Neurosurgery, Penn State University College of Medicine, Hershey, PA, United States
Here we present an olfactory fMRI data processing method that can significantly improve the data processing quality when the patients’ respiration pattern is not controlled and doesn’t synchronize with olfactory stimulation paradigm. As an example of implementation we present an olfactory fMRI examination while the subject’s respiration pattern is not regular. Our data demonstrates that it is critical to consider the subject’s respiratory patterns’ modulation on the olfactory stimulation paradigm. The presented olfactory fMRI data processing method can be used for various applications. In addition to the example of real time respiration data, subjective response data (not provided here) can also be convolved with odor delivery data for more improved fMRI data processing. This experimental set-up will be useful in the olfactory fMRI study of neuropsychiatric and neurologic patients that are not cooperative or be able to follow the breathing instructions.
Hsu-Lei Lee1, JÃ¼rgen Hennig1
1Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany
Physiological noise caused by ecg- and/or breathing related pulsatility may introduce temporal correlations that are unrelated to neuronal processes in a resting-state network analysis. As physiological noise is often non-linear and non-stationary, signal extracted by simple filtering will deviate from the actual noise, and so as global regression methods like RETROICOR. In this study we implemented empirical mode decomposition (EMD) on resting-state fMRI time-series and extracted cardiac components which has a time-frequency curve that well matches the true heart rate acquired by external ECG during the scan.
1163. Characterization and Correction of Physiological Instabilities in 3D FMRI
Rob Hendrikus Tijssen1, Steve M. Smith1, Peter Jezzard1, Robert Frost1, Mark Jenkinson1, Karla Loreen Miller1
1FMRIB Centre, Oxford University, Oxford, Oxon, United Kingdom
3D FMRI acquisitions have the advantage of allowing high resolution, isotropic, imaging. However, 3D acquisitions, such as SSFP and SPGR, show increased signal instabilities in the inferior regions of the brain. Here, we present a characterization of these temporal instabilities and propose a GRAPPA-based correction method that allows retrospective gating of 3D FMRI data.
1164. Length-Scale Dependent Effects of Noise Reduction in Phase and Magnitude FMRI Time-Series
Gisela E. Hagberg1, Marta Bianciardi2, Valentina Brainovich1, Antonino Maria Cassara3,4, Bruno Maraviglia3,4
1Santa Lucia Scientific Foundation, Rome, Italy; 2Advanced MRI Section, LFMI, NINDS, National Institutes of Health, Bethesda, MD, United States; 3Dept. Physics, Sapienza University, Rome, Italy; 4Centro Studi e Ricerche "Enrico Fermi"
fMRI analyses are primarily based on the magnitude information in gradient-echo echo-planar images (GE-EPI) but a growing number of studies also included the phase information. An issue relates to physiologic large-scale phase effects that are more prominent in phase than magnitude data. In the present work we explored the phase stability at different length scales at 3T and found that improvements in temporal stability could be achieved by alternative noise-reduction methods that take into account the differential origin of noise effects in phase and magnitude data.
1165. Comparison of Feature Selection Methods for Classification of Temporal FMRI Volumes Using SVM
Ayse Ece Ercan1, Esin Karahan2, Onur Ozyurt2, Cengizhan Ozturk2
1Biomedical Engineering, TU Delft, Delft, Netherlands; 2Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey
High dimensional feature space of fMRI volumes has been a drawback for classification studies since large feature dimension is known to increase the classification error and the computation time. In this study, we combined PCA with two anatomical feature selection methods: grey matter (GM) and region of interest (ROI) masking, and investigated the effects of different feature reduction methods on the classification accuracy of a linear SVM classifier. To apply PCA after anatomical masking is concluded to be a reliable method for preserving the classification accuracy of the anatomical feature selection methods and reducing the computation time.
1166. Assessment and Improvement of FMRI Normalization Based on Inversion-Recovery Prepared High-Resolution EPI
Pooja Gaur1, Helen Egger1, Nan-kuei Chen2
1Department of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, United States; 2Brain Imaging and Analysis Center, Duke University, Durham, NC, United States
EPI based fMRI has several major limitations: distortion, low spatial-resolution, and low anatomic resolvability. Therefore, it is not easy to register fMRI data to structural images, and to normalize fMRI data. EPI distortion correction and nonlinear normalization methods have been developed to address these limitations. However, it is not easy to assess how these methods perform on fMRI data with distortions, limited resolution, and anatomic resolvability. Here we report an imaging protocol based on high-resolution inversion-recovery prepared segmented EPI (with identical distortion patterns as in single-shot EPI), enabling accurate assessment of the performance for distortion correction and nonlinear normalization algorithm.
1167. Comparison of BOLD Response Modulation During Pain Stimulation and Resting-State Conditions Under Intravenous (0.2 Mg/70kg) or Sublingual (2 Mg) Buprenorphine Treatment
Jaymin Upadhyay1,2, Julie Anderson1,2, Adam J. Schwarz1,3, Richard Baumgartner1,4, Alexandre Coimbra1,5, Lauren Nutile1,2, James Bishop1,2, Ed George1,6, Brigitte Robertson1,7, Smriti Iyengar1,3, David Bleakman1,3, Richard Hargreaves1,5, Lino Becerra1,2, David Borsook1,2
1Imaging Consortium for Drug Development, Harvard Medical School, Belmont, MA, United States; 2P.A.I.N. Group; Brain Imaging Center, McLean Hospital, Belmont, MA, United States; 3Lilly Research Department, Eli Lilly and Company, Indianapolis, IN, United States; 4Biometrics Research Department, Merck Research Laboratories, Rahway, NJ, United States; 5Imaging Department, Merck Research Laboratories, West Point, PA, United States; 6Department of Anesthesiology and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States; 7Sepracor, Inc., Marlborough, MA, United States
Buprenorphine is commonly prescribed to treat pain. We implemented blood oxygenated-level dependent (BOLD) functional MRI to characterize and compare the effects of 2.0 mg (sublingual), 0.1 mg/70kg (intravenous) and 0.2 mg/70kg (intravenous) doses of buprenorphine on the central nervous system during pain processing and during the resting state. During pain processing, the 2.0 mg (sublingual) and 0.2 mg/70kg (intravenous) doses significantly (p<0.01) potentiated the BOLD response in regions such as the striatum, while attenuated the BOLD response in somatosensory cortices. Furthermore, the resting-state connectivity for sublingual and intravenous doses of buprenorphine were also altered among structures that mediate pain processing.
1168. Depth-Resolved Laminar Analysis of Resting-State Fluctuation Amplitude in High-Resolution 7T FMRI
Jonathan Rizzo Polimeni1, Douglas N. Greve1, Bruce Fischl1,2, Lawrence L. Wald1,3
1Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, United States; 2Computer Science and AI Lab (CSAIL), Massachusetts Institute of Technology, Cambridge, MA, United States; 3Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States
While voxels as small as 0.75 mm isotropic provide sufficient SNR for high-field fMRI, voxels falling within cortical gray matter voxels are still influenced by partial-volume contamination with white matter and CSF, which contribute different levels of physiological noise. Here we characterize the impact of partial-volume effects as a function of cortical depth on the resting-state fluctuation amplitudes at 7T. Even after partial-volume effects are taken into account, the magnitude of resting state fluctuations increases with proximity to the pial surface. This suggests that laminar differences in the resting-state fluctuations exist and may reflect increasing dominance of extravascular BOLD signal changes surrounding large pial vessels.
1169. Functional Connectivity During Memory Consolidation: A Resting-State FMRI Study
Chia-Wei Li1, Ke-Hsin Chen2, Tai-Li Chou2,3, Keng-Chen Liang2,3, Ya-Chih Yu1, Chang-Wei Wu1, Jy-Horng Chen1,3
1Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, Taiwan; 2Department of Psychology, National Taiwan University, Taipei, Taiwan; 3Center for Neurobiology and Cognitive Science, National Taiwan University, Taipei, Taiwan
Memory consolidation is a process which stabilizes a short-term memory into a long-term memory. Consolidation occurs after the initial learning lasting for a period of time. In this study, we employed resting-state experiment design to reveal the functional connectivity among hippocampus, PCC, and MTG during consolidation of memorizing easy and difficult words that would result in good and poor memory respectively. As seeds set at three ROIs, we detected increase connection with cuneus in the hard condition, implying the engagement of visual analysis; increment in connection with cerebellum and frontal cortex in the easy condition, reflecting the on-going consolidated activity.
1170. Assessing Functional Connectivity Measures at 3T and 7T
Joanne Rachel Hale1, Matthew Jon Brookes1, Emma Louise Hall1, Susan T. Francis1, Peter Gordon Morris1
1SPMMRC, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom
Functional connectivity, implied by inter-region correlation, has been reported in resting state BOLD activity. It is well known that as magnetic field strength is increased, BOLD contrast to noise is improved, implying that a move to high field would benefit functional connectivity measurement. However, fMRI signals are affected by non-neuronal artifacts which increase with field strength making the advantage of 7T questionable. Here, we assess non-neuronal physiological artifacts in 3T and 7T resting state data. Results show that sensorimotor cortex connectivity can be measured accurately and at high spatial resolution at 7T with little contribution from non-neuronal physiological artifact.
1171. Prediction of Functional Connectivity from Structural Brain Connectivity
Fani Deligianni1, Emma C. Robinson1, Christian F. Beckmann1, David Sharp1, A. David Edwards1, Daniel Rueckert1
1Imperial College London, London, United Kingdom
Studies that examine the relationship of functional and structural connectivity are important in interpreting neurophysiological data. Although, a linear relationship between functional and structural connectivity has been demonstrated, there is no explicit attempt to quantitatively measure how well functional data can be predicted from structural data. Here, we predict functional connectivity from structural connectivity by utilizing a predictive model based on principal component analysis (PCA) and canonical correlation analysis (CCA).
1172. Resting-State Functional Connectivity Strength Depends on the Magnitude of Resting BOLD Fluctuations and Not Differences in CBF
Anna Leigh Rack-Gomer1,2, Joy Liau3, Thomas T. Liu1,2
1Bioengineering, UC San Diego, La Jolla, CA, United States; 2Center for Functional MRI, UC San Diego, La Jolla, CA, United States; 3School of Medicine , UC San Diego, La Jolla, CA, United States
Interpretation of inter-subject differences in resting-state functional connectivity is complicated by the BOLD signal’s dependence on vascular factors. We found functional connectivity strength to be correlated with resting-state fluctuation amplitude (RSFA) across healthy subjects, where RSFA has previously been shown to correspond to vascular reactivity within subjects. However, we did not find RSFA to be related to either the task-related cerebral blood flow (CBF) response or baseline CBF, suggesting that RSFA does not indicate vascular differences across subjects. Instead, RSFA may reflect true differences in spontaneous neural activity, which contribute to the normal variability found in resting-state functional connectivity.
1173. Spontaneous Increase in Neuronal Activity in the Resting State Is Associated with Increase in Blood Oxygenation
Shmuel Na'aman1, Sebastien Thomas1, Mirza Baig1, Peter O'Connor1, Amir Shmuel1,2
1MNI, Dept. of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada; 2Center for MR Research, U. of Minnesota, Minneapolis, MN, United States
Recent studies have demonstrated large amplitude spontaneous slow (< 0.1 Hz) fluctuations in functional-MRI (fMRI) signals in humans in the resting state. Despite the large body of human imaging literature on spontaneous activity and functional-connectivity in the resting state, the link to underlying neural activity remains tenuous. We show that spontaneous neurophysiological activity in rat S1FL includes events in which changes in local field potentials across cortical layers resemble the corresponding changes in response to sensory stimulation. These spontaneous neurophysiological events are accompanied by increases in blood oxygenation that peak approximately 5 s following the events.
1174. Resting-State FMRI After Experimental Hemispherectomy in Rats: Changes in Functional Connectivity and Network Synchronization
Willem M. Otte1,2, Rick M. Dijkhuizen2, Peter C. van Rijen1, Peter H. Gosselaar1, Maurits P.A. van Meer1,2, Onno van Nieuwenhuizen1, Kees P.J. Braun1
1Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, Netherlands; 2Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands
Hemispherectomy is a last resort treatment for catastrophic hemispheric epilepsy. The remarkable motor recovery after hemispherectomy reflects the plastic capacities of the brain. We studied the remaining brain in hemispherectomized rats, 7 and 49 days post surgery using resting-state fMRI, graph analysis and interregional connectivity. The sensorimotor cortex and striatum in the healthy contralesional hemisphere exhibited significantly increased functional connectivity after surgery. The graph analysis results assume a shift toward a more regular network organization. We have shown that rs-fMRI, connectivity analyses and specific network measures can provide unique insights into functional reorganization in the remaining brain after experimental hemispherectomy.
1175. The Non-Linear Dynamic Characteristics of Olfactory BOLD Response
Christopher W. Weitekamp1, Jianli Wang1, Paul J. Eslinger2,3, Jeffrey Vesek1, Xiaoyu Sun1, James R. Connor4, Qing X. Yang1,4, Jianzhong Yin1, Martin A. Lindquist5
1Radiology, Penn State University College of Medicine, Hershey, PA, United States; 2Neurology, Penn State University College of Medicine, Hershey, PA, United States; 3Neural & Behavioral Sciences, Penn State University College of Medicine, Hershey, PA, United States; 4Neurosurgery, Penn State University College of Medicine, Hershey, PA, United States; 5Statistics, Columbia University, New York, NY, United States
This study examined the dynamic nonlinear BOLD response pattern in the primary olfactory cortex (POC) and associated brain structures during an olfactory fMRI paradigm. An intricate relationship among perception threshold, sensitivity, and habituation of the human olfactory system challenges the fundamental assumption of linearity in BOLD response. The goal of this study was to emphasize an unconventional nonlinear model of BOLD response through the use of olfactory fMRI and to suggest that such dynamic characteristics may extend to other neuronal systems with a feedback mechanism, profoundly impacting fMRI data acquisition/analysis and its clinical applications.
1176. The Dependency of Age-Related Change of Brain Activation on the Visual Stimuli - Demand-Reservation Balance
Toshiharu Nakai1, Makoto Miyakoshi1, Epifanio Bagarinao1, Masaki Yoshida2, Chikako Nakai3, Kayako Matsuo4
1Functional Brain Imaging Lab, National Center for Geriatrics and Gerontology, Ohbu, Aichi, Japan; 2Ophthalmology, The Jikei University, Tokyo, Japan; 3School of Health Sciences, Toyoshashi Sozo University, Toyohashi, Aichi; 4Psychology, National Taiwan University, Taipei, Taiwan
We evaluated the effect task demand for visual processing on the age-related change of the brain activation in healthy subjects. In the elderly subjects, the % HRF in V1 was reduced by the flickering checkerboard stimuli. By a visuo-motor translation task the % HRF in BA19/7/39 was increased in the elderly, while no significant difference of % HRF was detected between the two age groups in V1. HRF analysis suggested that age-related change of % HRF may depend on the existence of neuronal network to compensate the potential functional decline according to aging.
1177. Acute Vs. Tonic Muscular Pain: Changes in Cerebral Blood Flow as Imaged by Arterial Spin Labeling
Daron Gordon Owen1,2, Collin Franklin Clarke3, Sugantha Ganapathy3, Frank S. Prato1,4, Keith S. St. Lawrence1,2
1Imaging Program, Lawson Health Research Institute, London, Ontario, Canada; 2Medical Biophysics, The University of Western Ontario, London, Ontario, Canada; 3Anesthesia and Perioperative Medicine, The University of Western Ontario, London, Ontario, Canada; 4Imaging, St. Joseph's Hospital, London, Ontario, Canada
The cerebral representation of acute pain is well established, whereas that of tonic pain is not due to difficulties in applying functional imaging to prolonged stimuli. We used arterial spin labeling (ASL) to investigate the neural activation associated with tonic muscular pain. The use of ASL allows direct comparison between studies. Compared to our previous study incorporating both acute and tonic phases, we observed smaller CBF changes, and only in bilateral insula and frontal gyrus, despite similar pain levels. A likely explanation is that the acute phase of the previous study induced anxiety and distress, whereas our tonic pain stimulus did not.
1178. Age and Gender Effects on Whole Brain Cerebral Blood Flow in Adolescents
Ai-Ling Lin1, Timothy Q. Duong1, Peter T. Fox1, Douglas E. Williamson2
1Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States; 2Psychiatry, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
Both gender and have long been assumed to have effects on brain function and cerebral blood flow (CBF). However, the effects of gender and age on CBF have not well explored in adolescents. To increase our knowledge in this area, MRI techniques were employed to measure global CBF with 267 adolescents. Our result shows that significant difference in CBF was observed between 12 and 15 years of age. However, no significant main effects of gender were found in the study. The results provide better understanding of brain functions for adolescent across age and gender.
1179. A FMRI Study of Temporary Hearing Threshold Shift
Piotr Bogorodzki1, Tomasz Wolak2, Krzysztof Kochanek2, Ewa Piatkowska-Janko1, Piotr Skarzynski2, Adam Pilka2, Jozef Kotus3, Andrzej Czyzewski3
1Institute of Radioelectronics, Warsaw University of Technology, Warsaw, Poland; 2Institute of Physiology and Pathology of Hearing; 3Gdansk University of Technology, Gdansk, Poland
Several empirical studies have shown, that long lasting acoustic noise exposure causes on humans effect called Temporary Hearing Threshold Shift (TTS). This work presents results from 15 healthy subjects participating in a fMRI study of TTS consisting of two runs: â££preâ££ with silent GE EPI scanning and â££postâ££ identical to â££â££preâ££, but after 15min high volume noise exposure (causing a mean 12 dB TTS effect). Group level analysis showed activations in auditory cortex (T=13.3 in lh, and 10.45 in rh). A two-sample T-test fails for post>pre contrast, however detailed ROI analysis shows differences in sub-auditory areas.
1180. Functional Imaging of Observation of Action in Elite Archers Using Video of Western-Style Archery Task
Hui-jin Song1, Joo-hyun Kim1, Jeehye Seo1, Moon-jung Hwang2, Young-ju Lee2, Kyung Jin Suh3, Sung Woo Kim3, Young Hwan Lee4, Dong Soo Yoo5, Yongmin Chang1,6
1Medical & Biological Engineering, Kyungpook National University, Daegu, Korea, Republic of; 2GE healthcare, Seoul; 3Dongguk University, Gyungju; 4Radiology, College of Medicine, Catholic University, Daegu; 5Radiology, College of Medicine, Dankook University, Chunan; 6Diagnostic Radiology, Kyungpook National University, Daegu, Korea, Republic of
Although the mirror neuron system has been extensively studied, no functional imaging data are currently available to gain insight in the possible difference of the mirror system between experts and novices. Therefore, the aim of the present study is to investigate the differences of activation in the mirror neuron system during viewing tool use familiar to experts between expert archers and novice subjects. Our results demonstrated that expert archers showed strong activation in the mirror neuron system during viewing videos of Western-style archery relative to inexpert control subjects. Taken together, our data consistent with previous reports suggest that human mirror neuron system could contain representations of tool use and expand motor repertoire with tool use experiences.
1181. Localization of the Hand Motor Area Using BOLD and ASL FMRI
Marco Pimentel1, Pedro Vilela2, Inês Sousa3,4, Patricia Figueiredo3
1Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Lisbon, Portugal; 2Imaging Department, Hospital da Luz, Lisbon, Portugal; 3Instituto Superior Técnico, Lisbon, Portugal; 4Healthcare Sector, Siemens, S.A., Portugal
Previous studies have shown that ASL-based fMRI exhibits better spatial specificity than the most commonly used BOLD contrast. Here, we compared the localization of the hand motor area obtained by simultaneous ASL-BOLD fMRI and standard BOLD fMRI at 3T with well established anatomical landmarks, in a group of 15 healthy subjects. Our results indicate that the localization of the hand motor area obtained using ASL fMRI is significantly less variable and closer to the hand motor cortex anatomical landmarks than the one produced by BOLD fMRI. This supports the notion that ASL may more accurately localize brain activation than BOLD.
1182. Understanding Consciousness from Information and Integration Within the Thalamocortical System
Xiaolin Liu1, Jingsheng Zhou2, Anthony G. Hudetz3, Shi-Jiang Li1
1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States; 2Rehabilitation Department, Xuanwu Hospital Capital Medical University, Beijing, China; 3Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States
Understanding the neural mechanisms of consciousness requires identification of the nature of contributions from each of the potential neural correlates, which together generate a complete cognitive experience. We examined the specific and nonspecific thalamic connections in the brain based on the neuroanatomical findings implicating their respective functional roles in sustaining information and integration, which are essential to consciousness. Our results endorse the view that the thalamocortical system is essential to consciousness, and support the hypothesis that the nonspecific thalamic connections largely reflect brain regions that are responsible for information integration, potentially sustaining various awareness functions.
1183. Examining Structure and Function in a Cognitive Task
Jeffrey Thomas Duda1, Corey McMillan, Murray Grossman, James Gee
1Bioengineering, University of Pennsylvania, Philadelphia, PA, United States
Structure and function are examined in the language network with DT-MRI and BOLD fMRI during a cognitive task. Activated cortical regions are identified and used to determine activation levels in each subject. Additionally, the regions are used to identify fiber tracts of interest. Canonical correlation analysis is used to identify correlations between functional activation and average fractional anisotropy in the fiber tracts. For each correlation found, the highest weightings are found for cortical regions and a tract that connects to that region.
Dave Langers1, Pim van Dijk1
1Otorhinolaryngology, University Medical Center Groningen, Groningen, Netherlands
Scanner acoustic noise may detrimentally affect stimulus/task-evoked neural responses in fMRI. This has been reported for the unimodal and associative auditory systems, but also for the default mode network and other brain systems.
In the current experiment, the effects of scanner noise in resting state fMRI are studied. We find that similar independent components may be extracted with and without background scanner noise, both during active and resting states. However, the overall strength, spatial extent, and temporal dynamics of various neural components are affected by the presence of background noise. Our results both corroborate and extend previous findings in literature. More detailed specific findings for various brain systems will be presented.
1185. Neural Correlates of Feigned Hearing
Bradley McPherson1, Wayne Wilson2, David Copland3,4, Katie McMahon5
1Division of Speech and Hearing Sciences, Hong Kong University, China; 2Division of Audiology, University of Queensland, Australia; 3Centre for Clinical Research, University of Queensland, Australia; 4School of Health and Rehabilitation Sciences, University of Queensland, Australia; 5Centre for Magnetic Resonance, University of Queensland, Brisbane, Queensland, Australia
Can we use patterns of brain activity to detect when someone is feigning a hearing loss? To answer this question, we asked 15 adult participants to respond to pure tones and simple words correctly, incorrectly, randomly, or with the intent to feign a hearing loss.
1186. An FMRI Study of Memory Performance in Type 2 Diabetes Mellitus: A Twin Study
Amanda Wood1, Jian Chen2,3, Thanh G. Phan2, Kimberlea Cooper2, Stacey Litras2, Srikanth Velandai2
1Developmental and Functional Brain Imaging,Critical Care and Neuroscience, Murdoch Childrens Research Institute, Melbourne, VIC, Australia; 2Stroke and Ageing Research Group, Department of Medicine, Monash University, Melbourne, VIC, Australia; 3Developmental and Functional Brain Imaging,Critical Care and Neuroscience , Murdoch Childrens Research Institute, Melbourne, VIC, Australia
Type 2 Diabetes mellitus (DM) is linked to a greater risk of dementia, but the underlying mechanisms and brain regions involved are unknown. We conducted a co-twin (DM/non DM) case-control study of fMRI activation during a visual memory task. Non DM twins showed greater activation of temporal, parietal and occipital cortices suggesting involvement of these areas in DM pathology.
1187. Increased Sensitivity to the BOLD-FMRI Signal Response During Electrical Forepaw Stimulation in Mice Using a Cryogenic RF Probe
Christof Baltes*1, Simone Bosshard*1, Thomas Mueggler1,2, Markus Rudin1,3
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland; 2Pharmaceutical Research Neuroscience, F. Hoffmann-La Roche Ltd., Basel, Switzerland; 3Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
BOLD-fMRI in mice using electrical forepaw stimulation was performed with a cryogenic transceive RF probe and a room-temperature receive-only surface coil. The effect of the increased sensitivity of the cryogenic probe on detecting BOLD responses was analyzed. In fMRI experiments, a gain in image SNR and in temporal SNR of a factor of 3.10 and 1.77 was found, respectively. As further optimization parameter adjusting the thermal shield temperature of the cryogenic probe allows for altering baseline perfusion and accordingly BOLD responses. Cryogenic cooling reduces BOLD signal variations by a factor of 1.59 and therefore increases the statistical power of fMRI.
1188. Investigating Color Vision Using FMRI: Rodent Vs Primate
Andy Paul Salzwedel1, Matt Mauck2, James Kuchenbecker3, Chris Pawela1, James Hyde1, Maureen Neitz3, Jay Neitz3
1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States; 2Department of Ophthalmology, Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States; 3Ophthalmology, University of Washington, Seattle, WA, United States
In a comparative study, the visual pathways of two different animal models (rodent vs primate) were probed using high field strength (9.4T) fMRI. The primary goal of this research was to assay the color vision systems of these two species in hope of demonstrating the evolutionary homology thereof. Here we present several techniques that combine to form a unique overall method for probing this pathway; pharmacological intervention (AP4), precession fMRI compatible LED based stimuli, and intra-brain controls.
1189. Detectability of the BOLD Signal
Jozien Goense1, Hellmut Merkle2, Nikos Logothetis1,3
1Department of Physiology of Cognitive Processes, Max-Planck Institute for Biological Cybernetics, Tuebingen, Germany; 2Laboratory of Functional and Molecular Imaging, NINDS, NIH, Bethesda, MD, United States; 3Division of Imaging Science and Biomedical Engineering, University of Manchester, Manchester, United Kingdom
The BOLD signal is a weak signal, and hence if no BOLD signal is found in an area this does not necessarily mean there is no neural activity in that area. Signal dropout, artifacts, instability, physiological noise, RF-coil inhomogeneity etc. can all reduce the SNR locally leading to decreased detectability of the BOLD signal Here we illustrate that calculation of the spatial distribution of the detection for a given set of experimental conditions allows us to estimate the confidence by which absence of an fMRI signal can be interpreted as an absence of neural activity.
1190. BOLD FMRI of Anesthetized Baboons
Hsiao-Ying Wey1,2, Jinqi Li1, M. Michelle Leland3, Lisa Jones3, C Akos Szabo4, John W. Roby1, James T. Scribner1,2, Ghzawan M. Kroma2, Peter T. Fox1, Timothy Q. Duong1,2
1Research Imaging Institute, UT Health Science Center at San Antonio, San Antonio, TX, United States; 2Radiology, UT Health Science Center at San Antonio, San Antonio, TX, United States; 3Laboratory Animal Resources, UT Health Science Center at San Antonio, San Antonio, TX, United States; 4Neurology, UT Health Science Center at San Antonio, San Antonio, TX, United States
This study reports a robust anesthetized baboon model for BOLD fMRI studies on a clinical 3T human MRI scanner. BOLD fMRI of visual and somatosensory/motor stimulations in anesthetized baboons were investigated. Comparisons of BOLD fMRI sensitivity were made between isoflurane and ketamine anesthetics with and without paralytics. To our knowledge, this is the first report on baboon BOLD fMRI of visual and somatosensory/motor.
1191. Using T1 Map to Guide Functional MRI Study of Ipsilateral Somatosensory Cortex in Awake Non-Human Primates
Junjie V. Liu1, Nicholas A. Bock2, Ara Kocharyan1, Julie Mackel1, Afonso C. Silva1
1NINDS, National Institutes of Health, Bethesda, MD, United States; 2Medical Physics, McMaster University, Hamilton, ON, Canada
By combining BOLD fMRI with T1 mapping, here we study the ipsilateral responses in somatosensory cortex of awake marmosets. Our results show a surprising spatial mismatch between contralateral and ipsilateral representations of the same body part.
1192. Fine -Scale Functional Connectivity Network Revealed at High Field (9.4T) Within Somatosensory Cortices of Anesthetized New World Monkeys
Arabinda Mishra1, Baxter P. Rogers1, Barbara Dillenburger1, Kevin Wilson1, Feng Wang1, John C. Gore1, Li Min Chen1
1Radiology & Radiological Science, VUIIS, Nashville, TN, United States
Correlations between resting state BOLD signals in widely distributed brain regions is a key signature of consciously driven mental activity in humans. In this work we attempted to explore if a fine scale functional connectivity can be detected within the anatomically well defined primary somatosensory cortex (SI) at high field and whether the functional connectivity reflects anatomical hierarchical relationships in anesthetized monkeys. We found that functional connectivity exists among anatomically interconnected cortical subregions (areas 3a, 3b, 1 and 2) within SI without the involvement of consciousness (or alertness), and the strengths of the correlation among these subregions reflect the strength of their underlying anatomical connections.
1193. fMRI Analysis of the Olfactory Responses to Home-Stream Water in Sockeye Salmon
Hiroshi Bandoh1, Ikuhiro Kida2, Hiroshi Ueda1,3
1Division of Environmental Science Development, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, Japan; 2Integrated Neuroscience Research Team, Tokyo Institute of Pschiatry, Setagaya-ku, Tokyo, Japan; 3Laboratory of Aquatic Ecosystem Conservation, Field Science Center for Northern Biosphere, Hokkaido University, Sapporo, Hokkaido, Japan
The odor-information processing involved in olfactory imprinting and homing of the home-stream odor in the central nervous system of salmon has not been completely elucidated. In this study, to investigate this information-processing mechanism, we used BOLD fMRI to measure the response to home-stream water in the olfactory bulb and telencephalon of sockeye salmon. The presence of BOLD signals in the dorsal area of the telencephalon indicated that the odor information for home-stream water was processed in a specific area in the telencephalon of sockeye salmon.
1194. Evaluation of Functional Deficit and Recovery in the Rat Somatosensory Cortex After Moderate Traumatic Brain Injury Using FMRI
Juha-Pekka Niskanen1,2, Antti Airaksinen1, Jari Nissinen1, Asla Pitkänen1, Olli Gröhn1
1Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland; 2Department of Physics, University of Kuopio, Kuopio, Finland
Traumatic brain injury (TBI) is a major cause of death and disability worldwide. In this study, 10 rats with TBI and 6 sham operated controls were imaged during electrical stimulation of the forepaws before TBI and 1, 2 and 8 weeks after TBI. fMRI with forepaw stimulation was able to reveal functional deficit after TBI in the somatosensory cortex outside of the main lesion and also detect partial sensory recovery 8 weeks after TBI. The results suggest that fMRI could serve as a non-invasive user independent tool to evaluate functional recovery after TBI.
1195. Complexity in the Spatiotemporal Hemodynamic Response to Sensory Stimulation in the Un-Anesthetized Rat
Christopher James Martin1, Jason Berwick2, Ying Zheng2, John Mayhew2
1Radiation Oncology and Biology, University of Oxford, Oxford, Oxfordshire, United Kingdom; 2University of Sheffield
The aim of this work was to investigate the spatiotemporal changes in hemodynamics that underlie fMRI signal changes in response to stimulus evoked changes in neuronal activity. We used optical imaging spectroscopy in an un-anesthetized rat model, to provide measures of changes in blood volume and oxygenation at higher spatial and temporal resolution than possible with fMRI, without the potentially confounding effects of anesthesia. We found a complex spatiotemporal hemodynamic response function, consisting of both increases and decreases in blood volume and oxygenation as well as oscillatory response components. We discuss the implications of these findings for fMRI.
1196. BOLD Changes in Somatosensory Cortex of Malnourished Rats
R Martin1, R Godinez1, Alfredo O. Rodriguez1
1Departament of Electrical Engineering, Universidad Autonoma Metropolitana Iztapalapa, Mexico, DF, Mexico
Malnutrition is a main public health problem in developing countries. Incidence is increasing and the mortality rate is still high. Functional Magnetic Resonance Imaging (BOLD) was used for mapping brain activity of malnourished rats. The food competition method was applied to a rat model to provoke malnutrition during lactation. The vibrissae-barrel axis was also used due to its advantages for studying structure, function, development and plasticity within the somatosensory cortex. BOLD response changes caused by the trigeminal nerve stimulation on brain activity of malnourished and control rats were obtained at 7T. Results showed a major neuronal activity in malnourished rats.
Dewen Yang1, Zhiyong Xie1, James Goodman1, Anne Burkholder2, Nancy Poy2
1BioImaging COE, Pifizer Global Research & Development, Groton, CT, United States; 2WW Comparative Medicine, Pifizer Global Research & Development, Groton, CT, United States
The neurovascular response to electric forepaw stimulation (EFS) was observed with BOLD signal in the contralateral somatosensory cortex in 11 rats with normal blood gas physiology under alpha-chloralose anesthesia. Serial CBF maps were also acquired during EFS in a subset of these rats. BOLD activation and CBF maps showed elevated blood flow in the contralateral somatosensory cortex at the time of stimulation, after which the regional activation and increases in CBF spread to cortex in the ipsilateral hemisphere.
1198. Reduced BOLD Response in Mice Lacking Nociceptor Specific Sodium Channels (Nav1.7) Indicates Altered Pain Processing
Simone Claudia Bosshard1, Christof Baltes1, Markus Rudin1,2
1Institute for Biomedical Engineering, ETH Zürich, Zurich, Switzerland; 2Institute of Pharmacology and Toxicology, University of Zurich, Zurich, 8057, Switzerland
Electrical stimulation of the forepaws is a widely used stimulation paradigm in functional magnetic resonance imaging (fMRI). We used transgenic mice lacking the voltage-gated sodium channel Nav 1.7 specifically at the nociceptors (Nav1.7R-/-) to study altered pain sensitivity. Nav1.7R-/-, WT littermates and WT animals of our lab were examined using BOLD fMRI. The detected BOLD signal changes of the Nav1.7R-/- animals were significantly reduced as compared to the two WT groups. This is in line with behavioral data reported for these mice. This proves our method to be a valuable tool to non-invasively study pain processing in mice.
1199. BOLD Response and Associated Metabolic Changes in the Rat Barrel Cortex Following Sustained Trigeminal Nerve Stimulation
Nathalie Just1,2, Hanne Frenkel3, Rolf Gruetter3,4
1LIFMET, CIBM, EPFL, Lausanne, Switzerland; 2Department of Radiology, UNIL, Lausanne, Switzerland; 3LIFMET, EPFL, Lausanne, Switzerland; 4Department of Radiology, UNIL and HUG, Lausanne and Geneva, Switzerland
The present study examined the BOLD fMRI response of the rat barrel cortex upon sustained trigeminal nerve stimulation. Moreover, the alterations in the barrel cortex metabolite concentration due to prolonged functional activation were measured using 1H-MRS at 9.4T. The results demonstrate that sustained BOLD responses can be obtained reproducibly in the rat barrel cortex following prolonged trigeminal nerve stimulation. Furthermore, preliminary functional MRS (fMRS) results show changes in several metabolites in the barrel cortex and in particular an increase in lactate levels during barrel cortex activation.
1200. The Utility of FMRI in Measuring Brain Plasticity Following Peripheral Nerve Injury
Christopher Paul Pawela1,2, Bharat B. Biswal3, Rupeng Li2, Anthony G. Hudetz4, Hani S. Matloub1, James S. Hyde2
1Department of Plastic Surgery, Medical College of Wisconsin, Milwaukee, WI, United States; 2Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States; 3Department of Radiology, University of Medicine and Dentistry of New Jersey, Newark, NJ, United States; 4Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States
In this study brain reorganization following nerve injury and repair was followed for a twelve week period with BOLD fMRI in a rat model. Primary sensory functional return progressed over the entire study period whereas thalamic areas did not functionally return until the twelve week time point. This study demonstrates the utility of using BOLD fMRI as a substitute for conventional electrophysiology in studies of brain plasticity and has many applications outside of peripheral nerve injury and repair.
1201. Investigating the Role of Transcallosal Projections in Mediating Neuroplasticity Following Injury in a Rat Using FMRI
Jennifer I. Wood1,2, Suresh E. Joel1,3, Michael T. McMahon1,2, James J. Pekar1,2, Galit Pelled, 2,4
1F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States; 2The Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, United States; 3The Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, United States; 4F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute , Baltimore, MD, United States
Human and animal studies suggest the involvement of the transcallosal projection in shaping neuroplasticity following injury may be crucial in dictating the rehabilitation probability. This study was designed to investigate the role of the transcallosal pathways in mediating neuroplasticity following injury in a rat model of sensory deprivation. Using fMRI, we have studied the time course and the age-dependency of which the transcallosal projections effect cortical reorganization. The results demonstrate that the transcallosal projections involvement in neuroplasticity varies dependent on the age and the time following the injury and may introduce a critical consideration when choosing the right rehabilitation strategy.
1202. BOLD FMRI Assessment of the Functional Response to Taste Stimulation in Rat Brain
Ikuhiro Kida1, Yoko Hoshi1, Yoshinobu Iguchi1
1Integrated Neuroscience Research Team, Tokyo Institute of Pschiatry, Setagaya-ku, Tokyo, Japan
Some aspects of taste information processing have not been conclusively clarified, such as the process by which the gustatory cortex uses spatial codes to characterize taste information.We used BOLD fMRI measurements obtained at 7 T in an animal system to investigate the process by which taste information is encoded. Sucrose yielded a reproducible BOLD signal increase in the gustatory cortex. During taste stimulation, BOLD signals were also detected in the lip region of the primary somatosensory cortex, secondary somatosensory cortex, and amygdalae. This is the first study that used BOLD fMRI to observe gustatory activation in the rat brain.
1203. Functional MRI of Cortico-Striato-Thalamal Circuit Using a Novel Flexible Polyimide-Based Microelectrode Array Implanted in Rodent Deep Brain
Pai-Feng Yang1, You-Yin Chen2, Jyh-Horng Chen1, Chen-Tung Yen3
1Electrical Engineering, National Taiwan University, Taipei, Taiwan; 2Electrical Engineering, National Chiao-Tung University, Hsinchu, Taiwan; 3Zoology, National Taiwan University, Taipei, Taiwan
This paper proposes a novel flexible MRI-compatible microelectrode array that leverages the stimulation and recording properties for neuroscience application. We perform functional MRI to investigate the cortico-striato-thalamal circuit with thalamic stimulation. Significant positive BOLD responses were observed in receptive field in upper lip region (S1ULp), barrel field (S1BF) and secondary somatosensory cortex (S2). Negative BOLD responses were revealed in caudate putamen (CPu). We inferred a limbic cortico-striatal loop might exist.
1204. A Non Invasive Experimental Protocol for FMRI Studies: Investigation of the Basal Ganglia-Cortex Circuit in a Rat Model
Salem Boussida1, Amidou Traore2, Jean-Pierre Renou2, Franck Durif3
1INRA, UR370 QuaPA/NMR plateforme, Centre Clermont-Ferrand/Theix, F-63122 Saint Genès Champanelle, France; 2INRA, UR370 QuaPA/NMR plateforme, Centre Clermont-Ferrand/Theix, F-63122 Saint Genès Champanelle, France; 3CHU Clermont-Ferrand, Service de Neurologie, Clermont-Ferrand, F-63001, France.
Combination of blood– oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) and electrical hindpaw stimulation has been used as a standard model to study the somatosensory pathway and brain rehabilitation in rats. In the present study, we examined the feasibility of performing BOLD fMRI experiments on rat to investigate the activity of the basal ganglia (BG)-cortex circuit associated to hindpaw sensitive stimulation. These findings will have relevance in the fMRI studies dealing with physiopathology of neurodegenerative diseases such as Parkinson
1205. Refining the Sensory and Motor Ratunculus of the Rodent Upper Extremity: Evaluation of the C7 Nerve Root Using FMRI and Direct Nerve Stimulation
Patrick C. Hettinger1, Rupeng Li2, Ji-Geng Yan1, Hani S. Matloub1, Young R. Cho1, Matthew L. Runquist2, Christopher P. Pawela1, James S. Hyde2
1Plastic Surgery, Medical College of Wisconsin, Milwaukee, WI, United States; 2Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States
The purpose of this study is to further define the ratunculus by observing cortical activity using BOLD fMRI during direct stimulation of the C7 nerve root. In this study, 7 Sprague-Dawley rats underwent implantable electrode placement on the C7 nerve root. BOLD response to nerve stimulation was then studied using a Bruker 9.4T MRI scanner. C7 nerve stimulation resulted in a small amount of activation in the S1FL region along with a large amount of activation within the M1/M2 regions. These findings are similar to the sensory and motor distributions described in human C7 nerve root literature.
1206. Functional MRI Detects Chronically Enhanced Somatosensory Activation Maps Following Multiple Seizures in Rats.
Ursula I. Tuor1, Jennifer Vuong2, Jeffrey F. Dunn3, Tadeusz Foniok1, Dave Kirk4, Amy H. Henderson2, G Campbell Teskey2,5
1Institute for Biodiagnostics (West), National Research Council of Canada , Calgary, Alberta, Canada; 2Psychology, University of Calgary; 3Radiology, University of Calgary; 4Experimental Imaging Centre, University of Calgary; 5Anatomy and Cell Biology, University of Calgary, Calgary, Alberta, Canada
We used functional magnetic resonance imaging (fMRI) in rats to investigate whether following 20 repeatedly elicited seizures there are seizure-induced alterations in the somatosensory maps to forepaw stimulation. We observed increased areas of activation both acutely (1-3 days) and chronically (3-5 weeks) after experimental kindling induced epilepsy. The data indicate that there is considerable neuroplasticity and development of new pathways during the progression of epilepsy. Whether comparable plasticity of cortical maps is present in humans should be tested using fMRI in future studies, considering that such seizure-induced changes may be involved in producing interictal behavioural disturbances.
1207. Layer-Specific FMRI of Photic Stimulation in the Rat Retina at 11.7 T
Yen-Yu Ian Shih1, Bryan H. De La Garza1, William J. Lavery1, Eric R. Muir1,2, Timothy Q. Duong1
1Research Imaging Institute, Ophthalmology/Radiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States; 2Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, United States
The retina is about 276 micron thick including the choroid and has highly organized laminar structures. This study reports, for the first time, the feasibility of high-resolution blood-volume fMRI to image layer specific (retinal and choroidal) visual responses in the rat retina at 11.7T up to 40x40x600 micron nominal resolution. Given that the choroid is behind the retina and the retinal pigment epithelium, it is generally inaccessible by optical techniques. Blood-volume fMRI thus could provide a unique means to evaluate lamina-specific functional changes in the rat retina where many retinal disease models are readily available.
Eric Raymond Muir1,2, Sung-Hong Park3, Timothy Q. Duong2
1Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, United States; 2Research Imaging Institute, Ophthalmology/Radiology, UT Health Science Center San Antonio, San Antonio, TX, United States; 3Research Imaging Institute, Radiology, UT Health Science Center San Antonio, San Antonio, TX, United States
BOLD fMRI of the thin retina with the widely used EPI acquisition is challenging because the eye is a region of large magnetic inhomogeneity and high-resolution EPI is pushing the limits of gradient performance, resulting in susceptibility-induced signal drop out and image distortion. To overcome these limitations, we implemented a pass-band balanced steady state free precession (bSSFP) sequence for fMRI of the mouse retina at 45x45x500 µm. bSSFP has comparable temporal resolution and SNR per unit time as EPI, without the artifacts common in EPI. bSSFP fMRI could reliably detect layer-specific responses to hypoxic challenge in the mouse retina.
1209. Simultaneous FMRI and Long-Term in Vivo Electrochemistry (LIVE): Identifying the Neurochemical Correlates of Functional Imaging Signals
John Lowry1, Karen Griffin2, Stephen McHugh3, Nicola Sibson4
1Department of Chemistry, National University of Ireland, Maynooth, Ireland; 2University College Dublin, Ireland; 3Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom; 4Gray Institute for Radiation Oncology and Biology, University of Oxford, Oxford, Oxfordshire, United Kingdom
Long-term in-vivo electrochemistry (LIVE) enables real-time measurement of brain metabolites. Here we have simultaneously obtained BOLD fMRI and amperometric LIVE tissue oxygen data from rat cerebral cortex, during both increases and decreases in inspired oxygen. BOLD and tissue oxygen measurements demonstrated close correlation during both complete oxygen removal (negative responses) and increases in inspired oxygen (positive responses). Our findings demonstrate the feasibility of obtaining real-time metabolite information during fMRI acquisition. The results show that the BOLD signal provides a close correlate of the tissue oxygen dynamics or, alternatively, that tissue oxygen concentration can predict the magnitude of the BOLD response.
1210. Evaluation of Cerebral Energy Demand During Graded Hypercapnia
Stefan Alexandru Carp1, Maria Angela Franceschini1, David Alan Boas1, Young Ro Kim1
1Martinos Center/Radiology, Massachusetts General Hospital, Charlestown, MA, United States
The cerebral metabolic rate of oxygen (CMRO2) is a physiological parameter closely linked to neural activation as well as to various disease states. Hypercapnic calibration is used to calibrate the BOLD-CBF-CBV relationship under the assumption of iso-metabolic blood flow increase during CO2 inhalation. Simultaneous near infrared optical measurements of cerebral blood volume, blood flow and oxygen extraction can also be used to monitor CMRO2 changes, albeit at low spatial resolution. We use these optical measurements during graded hypercapnia to test the iso-metabolic assumption, and demonstrate an apparent increase in brain metabolism at higher inhaled CO2 levels.
1211. Dissociation of BOLD and Local Field Potentials
Wen-Ju Pan1, Matthew Magnuson1, Garth Thompson1, Waqas Majeed1, Dieter Jaeger2, Shella Keilholz1
1BME, Georgia Institute of Technology / Emory University, Atlanta, GA, United States; 2Biology, Emory University, Atlanta, GA, United States
To examine what extent consistence of the measurements between BOLD fMRI and local field potential (LFP), we evaluated BOLD and LFP simultaneously in rat somatosensory cortex with a combined measurement technique. The preliminary results indicated a dissociation between BOLD and LFP during low-level neural activity, which might mirror the limitation of neurovascular coupling, the bridge between BOLD and neural activity.
1212. TR and TE Dependence on Low Frequency BOLD Fluctuations
Matthew Evan Magnuson1, Wenju Pan1, Waqas Majeed1, Garth Thompson1, Shella Keilholz1
1Biomedical Engineering, Georgia Institute of Technology / Emory University, Atlanta, GA, United States
Low freqnecy fluctuations in resting state BOLD data have often been used to map functional connectivity in the rat brain. These low frequency BOLD fluctuations contain contributions from CBF, CBV, and CMRO2. Each of these components have unique physiological time signatures and effective echo times; therefore, modification of the TR and TE used in resting state scans should result in altered contributions from each BOLD component. In this study we examine the dependence of the selection of the TR and TE variables on low frequency resting state data.
1213. Further Test and Validation of Saturation-Recovery T1 MRI Measurement for Imaging Absolute CBF Change
Xiao Wang1, Xiao-hong Zhu1, Yi Zhang1, Wei Chen1
1Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States
The feasibility of saturation-recovery T1 MRI for imaging and quantifying absolute CBF change was further tested at 9.4T using a rat hypercapnia model on two aspects: using diffusion gradients to investigate macrovascular inflow contribution; and slab saturation with varied thickness to test the effects of blood transit distance on measuring CBF. The results indicate that the outcomes of CBF changes induced by hypercapnia were coincident with the literature reports, and not significantly affected by large-vessel inflow effect and blood transit time. The overall results demonstrate that the saturation-recovery T1 MRI is sensitive to microvascular perfusion; it provides a noninvasive and reliable imaging approach for studying cerebral perfusion changes induced by physiology or pathology perturbation.
1214. In Vivo MR Measurement of Arterial Pulse Pressure in the Murine Aorta
Volker Herold1, Marco Parczyk1, Wolfgang Rudolf Bauer2, Eberhard Rommel1, Peter Michael Jakob1
1Department of Physics EP5, University of Wuerzburg, Wuerzburg, Bayern, Germany; 2Medizinische Universitätsklinik, University of Wuerzburg, Wuerzburg, Bayern, Germany
Mouse models are increasingly used to investigate functional and cardiovascular parameters. In this work we present an approach to noninvasively estimate the arterial pulse pressure by measuring the time dependant blood flow pulse and the local pulse wave velocity. By determining the complex impedance with solutions from the Navier-Stokes equations for incompressible fluids, the pressure pulse could be calculated from the accordant flow pulse. The present results are in good agreement with results from the literature obtained by invasive methods.
1215. Problems for Motion Correction: Paradigm Correlated Motion Remains a Confounding Source for FMRI Artefacts.
Lubos Budinsky1, Benito de Celis Alonso2, Marina Sergejeva1, Andreas Hess2
1Institute of Pharmacology, FAU, Erlangen, Germany; 2Institute of Pharmacology, FAU, Erlangen, Germany
The undesired motion, which is correlated with the fMRI paradigm (often present in experiments which are using mechanical stimulation or painful stimulus) can create false areas of an activity, which could remain real BOLD activity areas and a signal time course. Here we present series of fMRI experiment with phantoms and dead animals to which the motion was induced by using an air driven device integrated into the animal cradle. Using results from these experiments we suggest strategy, how to deal with this problem even if conventional motion correction algorithm are not able to remove these false areas completely.
1216. Functional MRI in the Rat at 9.4 T and 16.4 T
David Zsolt Balla1, Hannes M. Wiesner1, Gunamony Shajan1, Rolf Pohmann1
1High Field Magnetic Resonance Center, Max Planck Insitute for Biological Cybernetics, Tübingen, Baden-Württemberg, Germany
Functional MRI (fMRI) in animals at high magnetic fields keeps expanding our knowledge about the basics of neural processing but the specificity of the fMRI-signal is still under ongoing investigation. Yet, as the signal to noise ratio in MRI depends linearly on the magnetic field strength and calls for even stronger magnets for the detection of even smaller anatomical details, the relation between the functional MR-response and field strength can only be approximated with complex models. In this study the blood oxygenation dependent (BOLD) effect was measured and compared at 9.4 T and 16.4 T in the same animal with segmented gradient-echo (GE) and spin-echo (SE) echo planar imaging (EPI) sequence using optimal echo times for the respective field. Furthermore, high resolution fMRI acquisition at 16.4 T was performed up to a 50 µm in-plane accuracy and for an 8 s temporal resolution without the use of cryo-coils or coil-arrays.
1217. BOLD, CBV, and CBF FMRI of Caudate Putamen in Rat Brain During Noxious Electrical Stimulation: Its Negative Hemodynamic Response to Neural Activities
Fuqiang Zhao1, Denise Welsh1, Mangay Williams1, Alexandre Coimbra1, Mark O. Urban2, Richard Hargreaves2, Jeffrey Evelhoch1, Donald S. Williams1
1Imaging Department, Merck Research Laboratories, West Point, PA, United States; 2Neuroscience Department, Merck Research Laboratories, West Point, PA, United States
In central nervous system, neuronal activity generally leads to increases in local venous blood oxygenation level (BOLD), cerebral blood flow (CBF), and cerebral blood volume (CBV). However, previous studies have reported that the neural activity in rat caudate putamen (CPu) during noxious electrical stimulation (NES) of paws causes BOLD and CBV decreases. To further understand the specific hemodynamic response in this anatomical structure and its temporal characteristics, BOLD, CBV, and CBF fMRI studies were performed in a rat brain slice containing the CPu. Our results suggest that the neural activity in the CPu during NES causes decreases in CBV and CBF, and an increase in CMRO2 which lasts >2 minutes after stopping the NES.
1218. fMRI at 17.6 T and Optical Fiber-Based Ca2+-Imaging in Rodents
Albrecht Stroh1, Florian Schmid2, Afra Wohlschlaeger3, Valentin Riedl4, Jenny Kressel3, Cornelius Faber2
1Department of Neuroradiology, Technical University Munich, Munich, Germany; 2Institute for Clinical Radiology, University Hospital Münster, Münster, Germany; 3Department of Neuroradiology, Technical University Munich, Germany; 4Department of Neurology, Technical University Munich, Germany
n this study we tested the feasibility of rat fMRI at highest field strength in combination with an implanted optical fiber. We aim for the combination of fiber based optical Ca2+ imaging with functional magnetic resonance imaging (fMRI) at 17.6 T in vivo. We increased the temporal resolution of fMRI to 20 ms by applying k-space segmentation. Additionally, we conducted fiber-based Ca2+ imaging in mice upon electric forepaw stimulation, detecting neuronal population activity. Our study indicates that a multimodal approach combining a global method like fMRI with a spatially confined, highly specific method as optical Ca2+ imaging becomes amenable.
1219. Layer Specific Detection of Inhibitory FMRI Response in Somatosensory Cortex Through Cortico-Cortical Interaction in Rats
Yoshiyuki Hirano1, Alan P. Koretsky2, Afonso C. Silva1
1CMU, LFMI, NINDS, NIH, Bethesda, MD, United States; 2FMMS, LFMI, NINDS, NIH, Bethesda, MD, United States
We investigated the laminar dependence of cortico-cortical interactions induced by paired bi-lateral somatosensory stimulation in α-chloralose anesthetized rats. When compared to the response obtained at 0 ms ISI, the BOLD percent signal change in the S1FL responding to the late stimulus was decreased by 47 % at 40 ms ISI. The degree of suppression in layers III to V was stronger than suppression of fMRI changes in layers I-II and in bottom of layer VI. Our data shows that BOLD fMRI has sufficient spatial and temporal resolution to study cortical circuits, within functional columns and layers.
Benito de Celis Alonso1, Tanya Makarova1, Andreas Hess1
1Pharmacology and Toxicology, FAU Erlangen Nuremberg, Erlangen, Bayern, Germany
Animal experimentation in neurosciences requires the use of anesthetics for animal welfare and cooperation. Two of the most widely used anesthetics for functional magnetic resonance imaging (fMRI) of animals are Isofluorane (Iso) and Alpha-Chloralose (AC). Iso is an volatile drug shown to be suitable to obtain fMRI images at low concentrations(1). AC is an injectable anesthetic with strong functional-metabolic coupling but can create physiological problems. Therefore, it has been used as a non recoverable. There are studies were AC was used on human patients and others were AC was used to anaesthetize and recover dogs and cats (2,3). To our knowledge, the non-recoverable concept has not been challenged properly for fMRI. Here we present a protocol for AC anesthetic preparation and a fMRI study that shows that AC can be used as a recoverable anesthetic and has no effects on the fMRI results when animals are reused. Furthermore parallel behavioral studies on recovered rats show no effect on their brain and motor function.
1221. Noradrenergic Modulation of Auditory Processing in the Songbird Brain.
Colline Poirier1, Tiny Boumans1, Michiel Vellema1, Geert De Groof1, Marleen Verhoye1, Jacques Balthazart2, Annemie Van der Linden1
1Bio-Imaging Lab, Antwerp, Belgium; 2GIGA Neurosciences, Liège, Belgium
Song learning in songbirds shares a large number of features with human speech acquisition. The songbird brain is thus an excellent model to study the neural bases of vocal learning and complex sound processing. The aim of this spin-echo BOLD fMRI study was to investigate the role of noradrenalin in conspecific songs and bird’s own song perception. Depletion of noradrenergic inputs resulted in an enhanced differential activation by socially relevant auditory stimuli in the secondary auditory regions of the songbird brain. These results suggest that noradrenalin might play an inhibitory role in song discrimination.
1222. Role of Nitrite in Neurovascular Coupling: Nitric Oxide-Dependent and Independent Mechanisms
Barbora Piknova1, Ara Kocharyan2, Alan N. Schechter1, Afonso C. Silva2
1National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States; 2National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
In addition to classic role of vasodilator, nitric oxide (NO) also acts as a neurotransmitter. NO role in neurovascular coupling and the possibility to restore the proper brain hemodynamics after its impairment in various NO-deficiency related diseases is of major importance. We studied the fMRI response to forepaw stimulation on á-chloralose anesthetized Sprague-Dawley rats at baseline, with NO production attenuated by nNOS inhibition and after NO and nitrite distribution. We found that exogenous NO and nitrite restore neurovascular response and that nitrite is more effective than direct NO donor. We hypothesize about additional vasodilatory pathways in case of nitrite metabolism.
1223. Qualitative Differences in the Brain Activation Effects of Cocaine and Mdma Determined with Bold Fmri in Rhesus Monkeys
Kevin Sean Murnane1, Leonard Lee Howell1
1Neuroscience, Emory University, Atlanta, GA, United States
Both cocaine and methylenedioxymethamphetamine (MDMA) are drugs with a high propensity for abuse yet they have distinct behavioral and neurochemical effects. We compared the changes in blood oxygenation elicited by cocaine (0.3 mg/kg, i.v.) and MDMA (0.3 mg/kg, i.v.) in rhesus monkeys using BOLD fMRI. The effects of cocaine were localized to dorsal prefrontal cortex (PFC) whereas MDMA’s were localized to ventral PFC. Therefore, the neural circuitry engaged by these compounds appears to regulate their behavioral effects. As such, the use of fMRI allows for a novel approach to determine the mechanism of drugs of abuse.
1224. De Novo Buprenorphine Phmri Effects in Conscious Rats Parallels Brain Activation in Humans
Lino Becerra1,2, Pei-Ching Chang1, James Bishop1, Jaymin Upadhyay1, Julie Anderson1, Gautam Pendse1, Smriti Iyengar3, Alexandre Coimbra4, Richard Baumgartner4, Adam Schwarz3, Jeffrey Evelhoch4, Erci Nisenbaum3, Brigitte Robertson5, Thomas Large5, David Bleakman3, Richard Hargreaves4, David Borsook1,2
1Imaging Consortium for Drug Development, McLean Hospital, Belmont, MA, United States; 2A A Martinos Center for Biomed. Imaging, MGH, Harvard Medical School, Charlestown, MA, United States; 3Eli Lilly and Co., Indianapolis, IN, United States; 4Merck and Co, West Point, PA, United States; 5Sepracor Inc., Marlborough, MA, United States
fMRI studies of rodents are confounded by the use of anesthetics, especially for the study of analgesics. Furthermore, there are no studies comparing pharmacological brain effects in humans and rodents of the same analgesics. In this work, we present results of pharmacological MRI (phMRI) of an opioid analgesic (buprenorphine) in conscious rats and compare the brain activations with results obtained in humans. Although brain structure and function differ between humans and rodents, some parallelism does exist and this thesis underpins much pre-clinical research. Translational results as presented here have the potential to bridge pre-clinical with clinical imaging studies.
1225. A FMRI Study to Decipher the Regional Effects of an Intraperitoneal Glucose Dose in the Fasted Rat Model
Kim O'Toole1, Diana Cash1, Steve C R Williams1, Po-Wah So1
1Neuroimaging Department, Institute of Psychiatry, KCL, London, United Kingdom
Glucosensing neurones regulate membrane potential and firing rates in response to ambient glucose levels, and generally located in areas involved in neuroendocrine function, nutrient metabolism and energy homeostasis. Using BOLD-MRI, we have studied the effects of a single intraperitoneal glucose tolerance dose in the brain of a fasted rat model. Glucose induced BOLD-MRI signal increases in various regions of the brain, including the hypothalamus and hippocampus, which are known to contain glucosensing neurones. Thus, BOLD-MRI may be used to a non-invasive tool assess the functional role of nutrients in the brain under different physiological states.
1226. Effect of the Novel Anti-Depressant Agomelatine Determined by Pharmacological MRI in the Rat.
Karen Elizabeth Davies1, Inna V. Linnik1, Shane Mckie2, Jennifer A. Stark3, Simon Luckman3, Laure Sequin4, Elisabeth Mocaer4, Mark Millan4, Bill Deakin2, Steve R. Williams1
1Imaging Science & Biomedical Engineering, University of Manchester, Manchester, United Kingdom; 2Neuroscience and Psychiatry Unit, University of Manchester, Manchester, United Kingdom; 3Faculty of Life Science, University of Manchester, Manchester, United Kingdom; 4Institut de Recherches Internationales, Servier, Courbevoie, France
phMRI was used to determine brain areas activated by the novel anti-depressant agomelatine at 3 doses. T2*-weighted GE images were acquired continuously before and after injection of agomelatine or vehicle in isoflurane-anaesthetized rats. A pseudoblock analysis was performed in SPM5, revealing significant areas of activation and deactivation including cortical, hippocampal and caudate regions. There was a marked effect of dose with more brain areas, more total voxels and higher Z-scores at a dose of 20mg/kg compared to either 10 or 40mg/kg. Agomelatine acts at both melatonin and serotonin receptors and both receptors are likely to be involved in these responses.
1227. Concurrent Pharmacological MRI and Electrophysiology to Investigate Neuropharmacological Modulation of Brain Function in the Rat
Christopher James Martin1, Nicola R. Sibson1
1Radiation Oncology and Biology, University of Oxford, Oxford, Oxfordshire, United Kingdom
The aim of this work was to combine pharmacological magnetic resonance imaging with electrophysiological recording of neuronal activity such that we might improve our understanding of: (1) the neural basis of neuroimaging signals; (2) the effects of neuropharmacological manipulations on neurovascular coupling and neuroimaging signals; and (3) neuroanatomical differences in the relationship between neuronal activity and neuroimaging signals. We report data from studies in which we use the serotonin (5-HT) releasing agent fenfluramine to increase endogenous 5HT levels and investigate the effects of this modulation on both baseline and stimulus-evoked fMRI signals and neuronal activity.
1228. BOLD PhMRI in the Rat on a Clinical 3T Scanner Using Cocaine Challenge
Edwin Heijman1, Duncan Jack Hodkinson2, Roland van de Molengraaf3, Brian Henry4, Shane McKie5, Charles Sio1
1Philips Research Europe, Philips, Eindhoven, Netherlands; 2Imaging Science and Biomedical Engineering, The University of Manchester, Manchester, United Kingdom; 3Life Science Facilities, Philips Research, Philips, Eindhoven, Netherlands; 4Translational Medicine Research Centre, Schering-Plough, Singapore, Singapore; 5Neuroscience and Psychiatry Unit, The University of Manchester, Manchester, United Kingdom
In this study we investigated the potential applications of a clinical 3T system for pharmacological MRI (phMRI) in the rat brain. Using a human 3T MRI scanner, a dynamic SE-EPI BOLD sequence was implemented to determine alterations between pre- and post-injection of 5 mg/kg cocaine in male Sprague-Dawley rats under isoflurane anesthesia. Data analysis was performed using pseudoblock analyses. Cocaine-saline subtraction across the time series, showed significant activations in cortico-limibc areas of the motor, retrosplenial, and piriform cortex, extending to subcortical areas of the antero-dorsal hippocampus. We conclude that pre-clinical phMRI studies can be performed using 3T clinical scanners.
1229. Effects of Doxorubicin on Brain Activity and Functional Connectivity in Rats
Alan S. Bloom1, Peter S. LaViolette2, Christopher R. Chitambar3, William Collier1, Sally J. Durgerian4, Balaraman Kalyanaraman2, Donna M. McAllister2, Carol L. Williams1, Kathleen M. Schmainda5
1Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States; 2Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States; 3Neoplastic Diseases and Hematology, Medical College of Wisconsin, Milwaukee, WI, United States; 4Neurology, Medical College of Wisconsin, Milwaukee, WI, United States; 5Radiology and Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States
The purpose of this research was to investigate “chemobrain” at a mechanistic level by determining the effects of doxorubicin, one of the agents commonly used for the adjuvant chemotherapy of breast cancer, on brain function using fMRI and fcMRI in a rat model. . We observed in a small group of rats treated weekly with DOX that it alters brain activation by sensory stimulation particularly in regions associated with vision and that we are able to demonstrate resting state functional connectivity MRI in the anesthetized rat and that it is decreased by DOX treatment, particularly in the visual system.