White matter tract anatomy in the rhesus monkey: a fiber dissection study.

Brain connectivity in non-human primates (NHPs) has been mainly investigated using tracer techniques and functional connectivity studies. Data on structural connections are scarce and come from diffusion tensor imaging (DTI), since gross anatomical white matter dissection studies in the NHP are lacking. The current study aims to illustrate the course and topography of the major white matter tracts in the macaque using Klingler's fiber dissection. 10 hemispheres obtained from 5 primate brains (Macaca mulatta) were studied according to Klingler's fiber dissection technique. Dissection was performed in a stepwise mesial and lateral fashion exposing the course and topography of the major white matter bundles. Major white matter tracts in the NHP include the corona radiata, tracts of the sagittal stratum, the uncinate fasciculus, the cingulum and the fornix. Callosal fiber topography was homologous to the human brain with leg motor fibers running in the posterior half of the corpus callosum. The relative size of the anterior commissure was larger in the NHP. NHPs and humans share striking homologies with regard to the course and topography of the major white matter tracts.