|DTI of Neural Systems|
The Structural Core of Human Cerebral Cortex and Its
Relation to the Brain’s Default Network
Patric Hagmann1, Leila Cammoun2, Xavier Gigandet2, Reto Meuli1, Christopher J. Honey3, Olaf Sporns3
1University Hospital Center and University of Lausanne, Lausanne, Switzerland; 2Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; 3Indiana University, Bloomington, USA
Human cerebral cortex contains an uncertain number of structurally segregated regions interconnected by a dense network of axonal pathways. Using DSI, we map these pathways in individual human subjects. An analysis of the resulting large-scale structural brain networks reveals the existence of a core within the brain, as well as several distinct clusters. Regions within the structural core share high centrality and they form connector hubs that link all major modules of cortex. Most key regions of the human default network are also members of the structural core indicating an important role of the core in shaping functional integration.
Revealing the Topological Architecture of Human
Cortical Anatomical Network by DTI Tractography
Gaolang Gong1, Yong He2, Luis Concha1, Catherine Lebel1, Donald William Gross3, Alan Evans2, Christian Beaulieu1
1University of Alberta, Edmonton, Canada; 2McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University,, Montreal, Canada; 3Division of Neurology, Department of Medicine, University of Alberta,, Edmonton, Canada
An important issue in neuroscience is to reveal the architecture of complex brain network that might underlie fundamental structural and functional organization in the brain. This study employed DTI tractography to construct a macroscale anatomical network that captures the underlying common connectivity pattern of cerebral cortex across a population (N=80) of healthy young adults. This cortical network is found to exhibit small-world topology with the embedded pivotal nodes and connections mainly involving the association cortex regions and long-range white matter tracts, respectively. This finding might provide an insight into how anatomical connectivity of human brain underlies its functional states.
Rat Brain Connectivities After Stroke:
Combined Application of Diffusion Tensor MRI (DTI), Manganese Enhanced
MRI (MEMRI) and Functional MRI (FMRI)
Aurore Camille Bogaert1, Guadalupe Soria1, Mathias Hoehn1
1Max Planck Institut for Neurological Research, Cologne, Germany
The aims of the present study were to establish and apply an optimized experimental protocol to investigate cortico-thalamic connectivity, in rat brain after stroke, longitudinally in individuals. The combination of high spatial and temporal resolution DTI, MEMRI and fMRI showed us dynamic structural and functional deficits following stroke during the observation period of 8 weeks. Thus we observed loss of BOLD signal on the S1 cortex while diffusion anisotropy was decreased across a large part of the ischemic territory, as seen on DTI and FA maps. In agreement, MEMRI showed no manganese transport when the cortico-thalamic connectivity was disrupted.
Localization of Cognitive Function in Rats with
Magnetic Resonance Imaging
Tamar Blumenfeld-Katzir1, Ofer Pasternak1, Yaniv Assaf1
1Tel-Aviv University, Tel-Aviv, Israel
The brain localization of cognitive functions is limited to invasive lesion or electrophysiological studies. In this work we performed a diffusion tensor imaging study in rats. We correlated the FA and ADC indices with the rat's performance in a learning and memory task. We found that correlation between DTI indices and behavior performance is found in the limbic system: hippocampus, amygdale, olfactory complex and septum. These results imply that the cellular morphology of the limbic system correlates with learning and memory abilities of the rat.
Brain Localization of Cognitive Domains
with Diffusion MRI
Efrat Sasson1, Glen M. Doniger2, Ofer Pasternak1, Yaniv Assaf1
1Tel Aviv University, Tel Aviv, Israel; 2NeuroTrax Corporation, Newark, New Jersey, USA
In this study we investigated the relationship between changes in brain structures and cognitive performance in three cognitive domains – memory, verbal function, and information processing speed. Brains of 51 subjects age 25-82 were investigated using diffusion tensor imaging (DTI). Partial correlation was performed between ADC and the cognitive domains controlling for age, revealing a region-specific pattern of changes. The regions exhibiting substantial correlation in our study are known to play an important part in the corresponding functional domain. Thus, correlating cognitive performance and quantitative measures of brain morphology can be used for indirect functional localization of cognitive domain.
In Vivo Diffusion Spectrum Imaging
Disentangles White and Gray Matter Connectivity in the Human Cerebellum
Cristina Granziera1, Jeremy Dan Schmahmann2, Hubertus Fischer3, Thorsten Feiweier3, Karsten Jahns3, Heiko Meyer3, Reto Meuli1, Van J. Wedeen4, Gunnar Krueger5
1CHUV, Lausanne, Switzerland; 2MGH, Boston, Massachusetts, USA; 3Siemens Medical Solutions, Erlangen, Germany; 4Martinos' Center-MGH-Harvard medical school, Charlestown, Massachusetts, USA; 5Advanced Clinical Imaging Technology, Siemens Medical Solutions-CIBM, Lausanne, Switzerland
Numerous diseases such as ataxias, neoplasms, stroke and migraine affect the cerebellum, disrupting its highly complex brain structure. So far, most of the knowledge of cerebellar anatomy has been obtained through ex vivo approaches, structural MRI and Diffusion tensor imaging. These approaches, however, fail to accurately render cerebellar white and grey matter connectivity. In this study, we were able to disentangle for the first time in vivo cerebellar white and grey matter connectivity using diffusion spectrum imaging (DSI) at 3T. DSI clearly proofs to be a very promising technique to identify prognostic and monitoring markers of diseases affecting the cerebellum.
Segmentation of Sensory Pathways in Human
Trigeminal Ganglion and Brain Stem
Jaymin Upadhyay1, Jamie Knudsen1, Julie Anderson1, Lino Becerra1, David Borsook1, 2
1P.A.I.N. Group, Brain Imaging Center, McLean Hospital, Belmont, Massachusetts, USA; 2Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
Diffusion tensor probabilistic tractography was implemented to map sensory and pain pathways in human trigeminal ganglion and brain stem. Peripheral trigeminal nerve branches (V1, V2 and V3) were segmented at the level of the trigeminal ganglion. V1, V2 and V3 were found to converge to form the trigeminal nerve root, which enters the brain stem at the mid-pontine level and projects towards caudal pontine regions. Lastly, the spinal thalamic and trigeminal thalamic pathways within the brain stem were segmented. DTI-based segmentation of sensory and pain pathways was comparable to conventional histological findings in human trigeminal ganglion and brain stem.
Fiber Tracking of Cervical Spinal Cord and Nerves
Thomas Benner1, André J. W. van der Kouwe1, Denise P. Yates1, Graham C. Wiggins1, Ruopeng Wang1, Van J. Wedeen1, A. Gregory Sorensen1
1Athinoula A. Martinos Center, Charlestown, Massachusetts, USA
Feasibility of fiber tracking of human cervical spinal cord and nerves based on DTI was examined. DTI was performed at 3 T using a custom 8-channel coil placed in close proximity to the neck. A spatial resolution of 1.5x1.5x1.85 mm3 was achieved in 13 min. Fiber tracking and visualization were performed using custom-made programs. Spinal cord as well as nerves could be visualized well. This study shows that diffusion tractography has unique potential for imaging spinal cord and roots, and that the basic technical barriers to tractography in the peripheral nervous system can be overcome by using existing technologies.
Building an Atlas of the Subcortical White Matter:
Identification and Assignment of Common Anatomical Structures
Kenichi Oishi1, Karl Zilles, Katrin Amunts, Hangyi Jiang1, Xin Li, Kazi Akhter1, Kegang Hua1, Roger Woods, Arthur Toga, Gilbert Bruce Pike, Pedro Rosa-Neto, Alan Evans, Jiangyang Zhang1, Hao Huang1, Michael I. Miller, Peter C. van Zijl1, John Mazziotta, Susumu Mori1
1Johns Hopkins University, Baltimore, Maryland, USA
Anatomy of subcortical white matter (SWM), which bridges the deep white matter and the cortex, has not been comprehensively characterized in the past. In this study, we linearly normalized DTI data from 81 healthy subjects to the ICBM-152 coordinate space and identified common anatomical features in this region. We found that the SWM consisted of nine blade-like structures. These structures were parcellated and annotated in ICBM and Talairach spaces. Four U-fibers were also identified inter-connecting these 9 structures. This atlas is now available and is expected to enhance our understanding of involvement of the SWM in various brain diseases.
Implicit Reference-Based Group Registration of
Diffusion Tensor Imaging
Xiujuan Geng1, Hong Gu1, Thomas J. Ross1, Gary E. Christensen2, Yihong Yang1
1National Institute on Drug Abuse, NIH, Baltimore, Maryland, USA; 2The University of Iowa, Iowa City, Iowa, USA
An implicit reference-based group-wise (IRG) registration method was proposed and applied on population study of the fractional anisotropy (FA) derived from diffusion tensor imaging (DTI). This method does not require a template, and registers all images simultaneously to an implicit reference, which is the population mean in a general metric space. The results demonstrate that the IRG method has better performance in terms of smaller cross subject variance after registration compared to reference-based techniques. This may improve the sensitivity to detect subtle changes in white matter integrity between populations.