Abstract
Comparative neuroimaging has been used to identify changes in white matter architecture across primate species phylogenetically close to humans, but few have compared the phylogenetically distant species. Here, we acquired postmortem diffusion imaging data from ring-tailed lemurs (Lemur catta), black-capped squirrel monkeys (Saimiri boliviensis), and rhesus macaques (Macaca mulatta). We were able to establish templates and surfaces allowing us to investigate sulcal, cortical, and white matter anatomy. The results demonstrate an expansion of the frontal projections of the superior longitudinal fasciculus complex in squirrel monkeys and rhesus macaques compared to ring-tailed lemurs, which correlates with sulcal anatomy and the lemur’s smaller prefrontal granular cortex. The connectivity of the ventral pathway in the parietal region is also comparatively reduced in ring-tailed lemurs, with the posterior projections of the inferior longitudinal fasciculus not extending toward parietal cortical areas as in the other species. In the squirrel monkeys we note a very specific occipito-parietal anatomy that is apparent in their surface anatomy and the expansion of the posterior projections of the optical radiation. Our study supports the hypothesis that the connectivity of the prefrontal-parietal regions became relatively elaborated in the simian lineage after divergence from the prosimian lineage.
Highlights
Comparative neuroscience is an important approach for understanding general brain anatomy and function
The results demonstrate an expansion of the frontal projections of the superior longitudinal fasciculus complex in squirrel monkeys and rhesus macaques compared to ring-tailed lemurs, which correlates with sulcal anatomy and the lemur’s smaller prefrontal granular cortex
Cortical surface reconstructions reveal that all three species show some degree of cortical folding (Fig. 4A), but this is most apparent in the macaque, with the squirrel monkey showing the least evidence for deep sulci in the occipital, and to a lesser extent, frontal cortex
Summary
Comparative neuroscience is an important approach for understanding general brain anatomy and function. With the Platyrrhines (New World monkeys), the Cercopithecids and Hominoids form the infraorder Simiiformes (simian primates), thought to share extensive neuroanatomical similarities. Such similarities are the basis of the translational paradigm in neuroscience, using model species to understand the human brain. It is important to compare brain organization in a range of different species to understand how closely the neuroanatomy of traditional animal models parallels human brain organization, and to elucidate broader principles of neuroanatomical diversity across primates, and to reveal potential species-specific specializations
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