Training Induced Volume Changes Seen by Structural MRI Correlate with Neuronal Process Remodelling
Jason Philip Lerch¹, Adelaide P. Yiu², Alonso Martinez-Cabal², Tanyar Pekar², Veronique D. Bohbot³, Paul Frankland², R. Mark Henkelman¹, Sheena A. Josselyn², John G. Sled^1
1Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada; ²Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada; ³Douglas, Department of Psychiatry, McGill University, Montreal, Quebec, Canada

We correlated training induced volume changes seen by high-resolution mouse MRI with four cellular markers to test whether (1) alterations in neuron numbers/sizes; (2) alterations in astrocyte numbers/sizes; (3) increased neurogenesis/survival of new neurons; or (4) remodelling of neuronal processes best explain the MRI results. We detected a significant positive correlation between GAP-43 and structure volume, but found no correlation between MR volume and any other cellular measure. We can thus conclude that, among the hypotheses tested, the largest explanatory factor for learning induced MRI detectable volume changes is the remodelling of neuronal processes.

Do Congenitally Blind People Have a Stria of Gennari? First in Vivo Insights on a Subcortical Level
Robert Trampel¹, Derek Veit Ott¹, Robert Turner^1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

The primary visual cortex V1 is characterized by an easily identifiable anatomical landmark: the heavily myelinated stria of Gennari. Using T₁, T₂, T₂^* or phase contrast, high resolution MRI studies can routinely identify the stria of Gennari in vivo. However, the development and function of the Gennari stripe is unclear. MRI at 7 Tesla with isotropic 0.5 mm voxels was used to scan the occipital brain of sighted and congenitally blind subjects. The stria of Gennari was reliably detected in both sighted and blind subjects, showing that this anatomical feature is not a developmental result of visual input, and it does not degenerate in the absence of visual input.

Cerebral Myelin Content Correlation with Mathematical Abilities in Young Children
Richard Davis Holmes¹, Silvia Mazabel², Burkhard Maedler³, Christian Denk, Linda Siegel⁴, Christian Beaulieu⁵, Alex MacKay^6
1UBC MRI Research Centre, University of British Columbia, Vancouver, British Columbia, Canada; ²Department of Educational and Counselling Psychology, and Special Education, University of British Columbia; ³Philips Medical Systems; ⁴Department of Educational and Counselling Psychology and Special Education, University of British Columbia; ⁵Department of Biomedical Engineering, University of Alberta; ⁶Department of Physics and Astronomy, University of British Columbia

Structural imaging applied to children with wide ranging mathematical abilities has the potential to elucidate the question of what neural circuits underly computation based tasks. The present investigation analyzed the myelin water fraction images of 20 children in a standard space to deduce correlations between myelin content and math abilities. Subjects wrote a calculation-based test and an applied problem-based test. The results implicated occipital/parietal white matter, the  right anterior limb of the internal capsule and the left external capsule with positive correlations of 0.61,0.65 and 0.60, respectively.

Structural Brain Plasticity Visualized with Diffusion MRI Following a Learning and Memory Task
Tamar Blumenfeld-Katzir¹, Ofer Pasternak², Yaniv Assaf^1
1Neurobiology Department, Tel-Aviv University, Tel-Aviv, Israel; ²Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States

We utilized DTI to follow up on micro-structural changes that occur following a spatial memory task. We scanned rats before and after water maze task and compared their MRI scans using voxel-based statistics. Significant changes in the various DTI parameters were found in a multitude of brain regions including the limbic system and white matter systems. The changes in the DTI indices were found to correlate with immuno-reactivity staining of myelin, synapses and astrocytes. Using these observations, we conclude that DTI can be used as an in-vivo probe of structural plasticity both in gray matter and white matter.

Hard-Wired or Soft-Wired? Evidence for the Structural Plasticity of White Matter Networks Following Anterior Temporal Lobectomy
Mahinda Yogarajah¹, Niels Focke², Silvia Bonelli¹, Pam Thompson¹, Christian Vollmar¹, Andrew McEvoy³, Mark Symms¹, Matthias Koepp¹, John Duncan^1
1MRI Unit, National Society for Epilepsy, Chalfont St Peter, Bucks, United Kingdom; ²University of Goettingen, Germany; ³University College London Hospital, United Kingdom

Epilepsy is the most chronic, common neurological condition.  Many patients with temporal lobe epilepsy undergo anterior temporal lobe resection, but up to 40% of patients are at risk of language decline after surgery.  We carried out a longitudinal study using diffusion tensor imaging to assess the structural reorganisation of white matter after surgery.  In patients undergoing surgery in the language dominant hemisphere, there is an increase in FA in white matter connecting fronto-temporal regions.  The location of these increases and their correlation with language function suggest they may represent the structural plasticity of language networks after surgery.

Diffusion MRI of Short-Term Spatial Memory Related Brain Plasticity
Ido Tavor¹, Yaniv Sagi¹, Shir Hofstetter¹, Efrat Sasson¹, Yaniv Assaf^1
1Neurobiology, Tel Aviv university, Tel Aviv, Israel

Neuroimaging studies of brain plasticity reveal long-term learning related structural changes in several brain regions. Animal studies revealed that short term micro-structural changes can be observed with diffusion MRI. Here, we study the diffusion MRI changes in a short term spatial memory task in humans. Subjects underwent two MRI scans separated by two hours of a learning session. We found that DTI parameters had changed in several brain regions, including the hippocampus, entorhinal cortex, amygdala and insula. The main result of this work is that DTI can follow on learning-induced micro-structural tissue changes, already 2 hours following the training episode.

A Demonstration of Neural Plasticity in Resting Brain Network
Kuang-Chi Tung¹, Jinsoo Uh¹, Hanzhang Lu^1
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States

We hypothesized that an important feature of the evoked activity, the plasticity of the neural response, may also be present in the resting condition and may provide critical information for understanding the nature and significance of the resting state brain activity. Using motor cortex as a model, we demonstrated for the first time that the resting brain activity can be altered after repetitive stimulation of the associated brain networks. This method may provide a new approach to study brain plasticity in humans and may find applications in studies of aging and neurodegenerative diseases.

Unilateral Infraorbital Denervation Leads to Plasticity in the Rat Whisker Barrel Cortex
Xin Yu¹, Stephen J. Dodd¹, Seungsoo Chung¹, John Isaac¹, Judith R. Walters¹, Alan P. Koretsky^1
1NINDS, NIH, Bethesda, MD, United States

Interhemispheric plasticity may play a critical role during functional restoration following central/peripheral nervous system injuries in humans.  Previously, the interhemispheric plasticity in the rat somatosensory cortex (S1) following forepaw unilateral denervation has been studied in order to develop rodent models of plasticity detected in humans by fMRI. Here, the effects of unilateral infraorbital denervation (IO) to rat whisker responses were studied.  Large ipsilateral fMRI activation was detected after IO.  In addition, BOLD signals in the contralateral barrel cortex were significantly increased. This indicates that the unilateral IO caused plasticity of the whisker-barrel cortex ascending pathways and increased interhemispheric interactions.

fcMRI Plasticity Following Rat Median Nerve Injury and Repair at 9.4T
Rupeng Li¹, Patrick Hettinger², Younghoon Cho¹, Christopher P. Pawela¹, Maida Parkins², Seth Jones², Ji-Geng Yan², Andrzej Jesmanowicz¹, Anthony Hudetz³, Hani Matloub², James Hyde^1
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

Plasicity happening to the resting state connectivity map following rat peripheral nerve injury and repair was shown using 9.4T. Unique patterns of plasticity could help monitoring the neuro-network function when functional test in not available.