Allie Schrock (Duke University)

Most of our knowledge about primate neuroanatomy (e.g. major structuring of the brain) and neuroendocrinology (e.g. distribution of hormone receptors) owes to studies of anthropoid primates (e.g. rhesus macaques and titi monkeys). Despite accounting for a considerable proportion of primate species and socioecological diversity, strepsirrhines (or lemurs) are not well- studied, particularly not with regard to their brain structure and function. A broadly comparative, neuroanatomical study would help fill this gap. The present study relies on lemur brain samples acquired from the Duke Lemur Center through natural mortality, as well as freely available brain atlases of their closest relatives. There are two main goals: (1) Published and newly derived data will be used to describe the neuroanatomy of various strepsirrhines and compare it to that of rodents and anthropoids. Lemur brains are predicted to share some features with rodent brains and others with anthropoids, reflecting the lemurs’ phylogenetic position, evolutionary trajectories, and unique socioecologies. (2) Within lemurs, brain anatomy, and androgen and estrogen receptor densities, will be compared between the sexes in both female-dominant and egalitarian species. The purpose is to investigate the ‘masculinization’ hypothesis of female social dominance in lemurs, namely that sex steroid receptors underly female aggression in these unusual species. Female-dominant species are expected to differ from egalitarian species in their sexually dimorphic brain areas, and in their androgen and estrogen receptor distributions. Findings from this study will inform our understanding of primate evolution, lemur neuroanatomy and neuroendocrinology, particularly the brain’s role in regulating aggression.