Evolution of Neocortical Microcircuitry in Anthropoids

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Previous attempts to address the link between neural architecture and species differences in behavioral capacities have mostly relied on analysis of the size of the brain and its component structures. However, recent findings in the neurosciences have shown that more subtle alterations in neocortical circuitry can have profound effects on behavior and cognition. This research project aims to collect new data on neocortical microcircuitry across 15 species of anthropoid primates with the goal of more clearly understanding the biological basis of cognitive and behavioral specializations in humans and other primates. The researchers will examine phylogenetic variation in the organization of local-circuit GABAergic networks of the neocortex, a system that has significant influence on intracortical information processing. Stereologic data will be collected on interneuron subtype distributions identified by immunohistochemical staining for calcium-binding proteins representing primary sensory (Brodmann's areas 3b and 17), primary motor (area 4) and higher-order association regions (areas Tpt, 24b, 32, 44 and 45). In addition, microstructural data from Broca's area homologue (areas 44 and 45), Wernicke's area homologue (area Tpt), and the region of hand representation in primary motor cortex (area 4) will be assessed for patterns of asymmetry to test hypotheses concerning the evolutionary origins of language and handedness in humans. The results of this study will provide important insight into modes of reorganization in primate brain evolution and will help to elucidate the basis of functional neuroanatomic specializations in humans and other primates, such as theory of mind and language. This project will test the hypothesis that these cognitive adaptations are associated with departures from allometric trends or uniquely asymmetric changes in the intrinsic circuitry of particular neocortical areas. This project will have broader impacts by generating a shared archive of histological sections and slides representing various neocortical areas from many primate species which are rare in laboratory use. In addition, the equipment and resources developed in this project will strengthen infrastructure and student training opportunities in anthropology at Kent State University. Students at the undergraduate and graduate level will be engaged in research activities, gaining expertise in laboratory techniques, microscopy methods, and inquiry skills.