|Imaging Functional Networks in the Brain|
MIDAZOLAM SEDATION DISRUPTSTS the CORTICOLIMBIC
NETWORK CONNECTION: An FcMRI Study
Naranjargal Dashdorj1, Alexakis Charilaos1, Jaroslav Hlinka1, Rob Mason1, Quazi Siddiqui1, Dorothee Auer1
1University of Nottingham, Nottingham, UK
Functional neuroimaging modalities are increasingly applied to study functional connectivity (fc) defined as synchronisation of spatially remote neurophysiological events. Spontaneous low frequency fluctuations of the BOLD fMRI signal have been successfully used to study fc in the brain ‘at rest'. Advanced processing for spurious correlations allowed in recent years to characterise disease-specific alterations including the dysregulation of cortical-limbic circuitry in major depression. Moreover, cortico-limbic dysregulation as assessed by fc BOLD fMRI were found to be reversible after chronic antidepressant treatment.However, it remains unclear if and how acute pharmacological manipulations affect the functional connectivity between cortical-limbic networks. To our best knowledge, this is the first study investigating the effects of anxiolytic and sedative drug midazolam on fc in the cortico-limbic circuit in healthy volunteers.
An FMRI Study of Age Effects on Frontal-Striatal
Neural Circuit Functions
David C. Zhu1, Rose T. Zacks1, Jill M. Slade1
1Michigan State University, East Lansing, Michigan, USA
The frontal-striatal neural circuit is thought to be associated with attention and executive function. To understand the modification of this neural circuit with aging, a rapid-event related fMRI flanker paradigm was applied to study the difference between the young (age 20 ± 3 yrs) and older (age 74 ± 6 yrs) populations. This study found that various anatomical regions associated this circuit were modified with aging as reflected by either the amplitude or latency of the BOLD response.
Reliable Modeling of Resting-State Emotional Networks
in Major Depressive Disorder: Applicability of Exploratory Structural
Equation Modeling to Small Sample Sizes
George Andrew James1, Scott J. Peltier2, Richard Cameron Craddock3, Stephen M. LaConte4, Helen S. Mayberg3, Xiaoping P. Hu1
1Emory University and Georgia Tech, Atlanta, USA; 2University of Michigan, Ann Arbor, USA; 3Emory University, Atlanta, USA; 4Baylor College of Medicine, Houston, USA
Exploratory SEM evaluated the neural network mediating emotion for fMRI resting-state data with healthy (n=28) and depressed (n=5) samples. Jackknife and split-sample reliability testing assessed SEM validity. The winning model for controls consistently beat its closest rivals despite exclusion of 1-5 subjects. This model showed moderately negative influence of thalamus upon cingulate and reciprocal feedback loops within cingulate and within prefrontal cortices. Randomly splitting the sample into halves or quarters and repeating the analysis yielded qualitatively similar models. Yet depressed and control samples differed dramatically, thus demonstrating the feasibility of exploratory SEM for detecting functional differences despite small samples.
Better Recovery Following Stroke is Associated with
Normalization of Resting-State Connectivity
Ali-Mohammad Golestani1, Andrew Demchuk1, Bradley G. Goodyear1
1University of Calgary, Calgary, Canada
fMRI has not emerged as a tool to assess acute stroke, due to difficulties associated with patients performing tasks. We propose the strength of resting-state connections (connectivity) as an index of function that does not require tasks. Twelve stroke patients with a sensory-motor deficit underwent two MRI sessions (<24 hours and 90 days post-stroke). Eight fully recovered by day 90. Twelve healthy volunteers are also recruited. Connectivity in all patients at day0 was less than healthy controls. Recovered patients regained connectivity by day 90, whereas non-recovered patients did not. Connectivity may potentially link stroke injury with brain function and communication.
A 3 T Functional MRI Study of the Resting State
Networks in Aging
Paola Valsasina1, Maria A. Rocca1, Martina Absinta1, Antonia Ceccarelli1, Andrea Falini1, Giuseppe Scotti1, Giancarlo Comi1, Massimo Filippi1
1Scientific Institute and University Ospedale San Raffaele, Milan, Italy
Aim of this study was to investigate the influence of normal aging on resting state networks (RSN) using independent component analysis in a group of 49 healthy subjects, with age ranging from 20 to 69 years. Ten relevant RSN were detected: two visual RSN; two sensorimotor RSN; five fronto-parietal-temporal RSN -three bilateral and two lateralized to left and right, respectively, and one parietal RSN, that included the precuneus and the posterior cingulum. Correlations with age were found only for one visual and one sensorimotor RSN, suggesting that the different RSN of the healthy brain might respond differently to aging.
Altered Memory Network Organisation in Left Temporal
Lobe Epilepsy Associated with White Matter Structural Changes
Natalie Laura Voets1, Steve M. Smith2, Jane E. Adcock, Richard Stacey3, Yvonne Hart, Katherine Carpenter, Paul M. Matthews1, Christian F. Beckmann
1GSK, London, UK; 2Oxford University, FMRIB Centre, Oxford, UK; 3John Radcliffe Hospital, Oxford, UK
Memory reorganisation in temporal lobe epilepsy remains central to predicting surgical outcome. Recurrent seizures may arise as a result of aberrant connectivity within the mesial temporal lobes, resulting in altered structural coherence between regions of the memory network rather than hemispheric reorganisation per se. This study used TICA and voxel-wise diffusion analyses to identify altered structural coherence within the memory network in left temporal lobe epilepsy patients relative to healthy volunteers. These functional changes were related to white matter integrity along the contralesional uncinate fasciculus.
The Effect of Menstrual Cycle on Women’s Visceral
Jianli Wang1, Helena F. Wrzos, Christopher M. Collins1, Jelena Zinnanti, Wanzhan Liu, Qing Li, Paul J. Eslinger, Qing X. Yang1, Michael B. Smith1, Ann Ouyang
1Penn State College of Medicine, Hershey, Pennsylvania, USA
The effect of menstrual cycle on the brain response to the visceral pain stimulation was studied on eleven healthy women using fMRI. Although there was no significant subjective perception difference of the same level of visceral stimulation between the two menstrual phases, during the luteal phase there was a significant increase of brain activation responding to the visceral pain stimulation than during the follicular phase. This finding supports the notion that the visceral pain perception may be augmented during the luteal phase at the central nervous system level.
Increased Desire for Food When Fasted is Associated
with Increased FMRI Activation of the Ventral Striatum, Insula and
Anthony Peter Goldstone1, Christina Prechtl de Hernandez1, Kinan Muhammed1, Gabriel Bell1, Giuliana Durighel1, Emer Hughes1, Adam D. Waldman, 12, Jimmy D. Bell1
1Hammersmith Hospital, Imperial College, London, UK; 2Charing Cross Hospital, Imperial College Healthcare NHS Trust, London, UK
We examined how regional brain activity measured by fMRI varies with nutritional state (fasted vs. fed) when viewing food pictures. 18 non-obese healthy volunteers (age 19-36y) were scanned on 2 separate mornings after an overnight fast or 1hr after breakfast. There was significant activation of the ventral striatum, insula and amygdala when viewing high-calorie vs. object or high- vs. low-calorie pictures when fasted, but not when fed, which mirrored how appealing the pictures were rated. Increased hunger and desire for food when fasted vs. fed is associated with increased activation in brain regions involved in reward, cue-elicited craving and emotion.
Reduced Fronto-Hippocampal Connectivity in
Schizophrenia During Associative Learning: Relevance for NMDA-Mediated
Eric Murphy1, Matcheri S. Keshavan1, 2, Vaibhav A. Diwadkar1, 2
1Wayne State University SOM, Detroit, Michigan, USA; 2University of Pittsburgh SOM, Pittsburgh, Pennsylvania, USA
The hippocampus and prefrontal cortex are critical regions in the encoding-retrieval memory circuit. Both regions are impaired in schizophrenia, yet few studies have assessed their functional connectivity in the illness specifically during tasks of memory encoding. In our fMRI study, patients and controls participated in an associative memory task during which they iteratively learned the associations between objects and locations in space. Functional connectivity was assessed with seed voxels drawn in each subject from the cornu ammonis region in the right hippocampus. Contrast analyses showed reduced fronto-hippocampal connectivity in patients relative to controls during memory encoding.
Brain Functional Correlates of Accuracy and Reaction
Time During Performance of the Digit Symbol Substitution Test in the
Vijay K Venkatraman1, Howard J. Aizenstein, Jack Guralnik, Jeff D. Williamson, Marco Pahor, Lenore Launer, Anne B. Newman, Stephanie Studenski, Nancy Glynn, Caterina Rosano
1University of Pittsburgh, Pittsburgh, Pennsylvania, USA
Several previous functional MRI studies in the elderly have identified age-related increased prefrontal activation in association with working memory performance. The primary hypotheses accounting for the increased activation include compensation or dedifferentiation. This current study tests these competing models using the digit symbol substitution task, a task involving working memory and processing speed, which is particularly sensitive to cognitive changes associated with aging. The findings suggest that older adults engage distinct overlapping networks of fronto-parietal regions to perform the DSST with greater accuracy and shorter reaction times.