An anthropoid/strepsirrhine divergence in ventral visual stream connectivity.

The ventral visual stream has undergone extensive reorganization within the primate lineage. While some work has examined restructuring of the ventral prefrontal cortical gray matter across primates, comparative studies of white matter connectivity are lacking primarily due to difficulties in data acquisition and processing. Here, we present a data-driven approach to the study of white matter connectivity using postmortem diffusion magnetic resonance imaging (MRI) data. With this approach, we reconstruct anterior temporal-frontal and occipitotemporal-frontal connections across 2 anthropoids and 1 strepsirrhine: the rhesus macaque, the black-capped squirrel monkey, and the ring-tailed lemur. We find that the anthropoids exhibit more dorsal prefrontal innervation of these ventral visual connections. This study supports the hypothesis that anthropoid primates underwent extensive reorganization of both gray and white matter during their emergence as visual foragers in a complex ecological niche. The data-driven techniques presented here enable further research on white matter connectivity in previously understudied species.