Stereoscopic visual area connectivity: a diffusion tensor imaging study

Purpose To study the white matter tracts connecting the different stereoscopic visual areas of the brain by diffusion tensor imaging. Methods In a previous study, we identified the cortical activations to a visual 3D stimulation in 12 subjects using functional MRI (fMRI). These areas of cortical activations [V5, V6, lateral occipital complex (LOC) and intra parietal sulcus areas (IPS)] in addition to the lateral geniculate nucleus (LGN) and the primary visual area V1 were chosen as regions of interest (ROIs). We studied by deterministic tractography the connections existing between these ROIs. Results Found connections were divided into three groups. The first group entails the geniculo-extrastriate connections. LGN was connected to V5, V6, IPS and LOC. These fibers course in the inferior longitudinal fascicule. The second group comprises the associative fibers. V1 was connected to V5 and LOC through the transverse occipital fascicule on one hand, and, to V6 and IPS through the stratum proprium cuni on the other hand. Connections between V5 and LOC, and V6 and IPS course within the vertical occipital fascicule. The third group contains commissural fibers. Forceps major entailed the connections between both V1, both V6, both IPS and IPS and contralateral V6. LGN was connected to contralateral LGN, V1, V6, IPS and LOC. Conclusions We have elucidated numerous connections between the visual areas and the LGN. Generalization of these results to the remainder of the population must remain prudent due to the limited number of subjects in this study.