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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.