M.Sc Thesis

M.Sc StudentFarkash Gil
SubjectNeural Connectivity in the Visual System - A Study Based on
DTI and fMRI
DepartmentDepartment of Biomedical Engineering
Supervisor ASSOCIATE PROF. Moshe Gur
Full Thesis textFull thesis text - English Version


The visual field is perceived as a whole although each hemi-field is projected to a difference cerebral hemisphere. To investigate the role of the corpus callosum in this wholistic percept, we have investigated the axonal projections from the human primary visual cortex in each hemisphere to the opposite hemisphere. One such pathway for passing the visual information from V1 in the occipital cortex to the opposite hemisphere is via callosal connections running through the posterior splenium of the corpus callosum. In this work we have investigated the topography and distribution of these fibers using Diffusion Tensor Imaging (DTI) and tractography. Per each fiber that was detected by the probabilistic fiber tracking algorithm we recorded the tips location and checked the density of these tips in different areas along the banks of the calcarine sulcus. We found that in most cases the origins of callosal fibers are very scarce at the foveal areas of the calcarine sulcus and that most of the fiber tips are concentrated at the middle area along the eccentricity axis. The distribution of acallosal fibers along this axis is much more uniform. This finding clarifies the issue of foveal callosal fibers distribution in the primary visual cortex, which was unclear in previous DTI studies and also unclear in previous anatomical and electro-physiological studies. Our results support the theory that the central visual field is represented at both hemispheres.