Interhemispheric Connectivity of the Human Temporal Lobes

Much is known regarding the major white matter pathways connecting the right and left temporal lobes, which project through the posterior corpus callosum, the anterior commissure, and the dorsal hippocampal commissure. However, details about the spatial location of these tracts are unclear, including their exact course and proximity to cortical and subcortical structures, the spatial relations between corpus callosum and anterior commissure projections, and the caudal extent of transcallosal connections within the splenium. We present an atlas of these tracts derived from high angular resolution diffusion tractography maps, providing improved visualization of the spatial relationships of these tracts. The data show several new details, including branching of the transcallosal pathway into medial and lateral divisions, projections of the transcallosal pathway into the external capsule and claustrum, complex patterns of overlap and interdigitation of the transcallosal and anterior commissure tracts, distinct dorsal and ventral regions of the splenium with high tract densities, and absence of temporal lobe projections in the caudal third of the splenium. Intersection of individual tract probability maps with individual cortical surfaces were used to identify likely regions with relatively higher cortical termination densities. These data should be useful for planning surgical approaches involving the temporal lobe and for developing functional-anatomical models of processes that depend on interhemispheric temporal lobe integration, including speech perception, semantic memory, and social cognition. HighlightsO_LIInterhemispheric connections of the human temporal lobes were visualized using high angular resolution diffusion tensor imaging tractography. C_LIO_LIResults are displayed on serial orthogonal sections to reveal detailed spatial relationships. C_LIO_LICorpus callosum projections through the splenium form distinct dorsal and ventral bundles and are absent from the caudal splenium. C_LIO_LIThe transcallosal pathway consists of distinct medial and lateral divisions. C_LIO_LIThe results reveal projections to the external capsule and claustrum not previously described. C_LIO_LITranscallosal and anterior commissural pathways show complex patterns of overlap and interdigitation. C_LIO_LISurface mapping revealed areas with relatively high density of projections to the cortical surface. C_LI