Functional anatomy of interhemispheric cortical connections in the human brain.

Interhemsipheric interaction between the human cerebral hemispheres is served by abundant white-matter fibres in the human corpus callosum (CC). Damage to these fibres has notable behavioural and cognitive sequelae that depend on the exact location of the fibre loss. Until now, correlations between fibre loss and neurological disorders have been limited to post-mortem studies. Here we used probabilistic diffusion magnetic resonance imaging tractography to produce a two-dimensional map of the CC in the mid-sagittal plane. We observed an antero-posterior topography of interhemispheric tracts within the CC, consistent with our current neuroanatomical understanding of post-mortem studies in human. Callosal tract to the left and right hemispheres had comparable volume. Gender, a factor that is often reported to affect CC shape and geometry, also had no effect on the volume of the tracts. Our map showed high consistency across individuals. We propose that this map might be useful in the study of the effects of damage to human CC in neurodegenerative and cognitive disorders.