The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Associations between localized variation in brain anatomy and social behavior in healthy human subjects

MACKENZIE M. LOYET1, P. THOMAS SCHOENEMANN1, BRIAN B. AVANTS2 and JAMES C. GEE2.

1Department of Anthropology, Indiana University, 2Department of Radiology, University of Pennsylvania

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Understanding the relationship between brain structure and function is critical for interpreting evolutionary changes in the human brain. It has been suggested that social environments play a key role in this process and brain size has been shown to correlate with social group size across primate species. Studies have indicated a disproportionate elaboration in areas of the prefrontal cortex in hominin evolution. The prefrontal cortex is known to be relevant to social processing, which suggests that selection for social ability may have played a significant role in prefrontal elaboration. Thus, in order for selection on social abilities to result in evolutionary changes in brain morphology, there must have been genetic correlations within modern humans between brain anatomy and social ability. To assess this possibility, associations between localized brain anatomy and several behavioral measures related to social facility were determined on a sample of 36 female sibling pairs (72 subjects total). Voxel-based morphometric methods were used to quantify brain morphology in MRI scans, and self-reported degrees of social interaction/engagement were used as a proxy for sociality. A within-family analysis was used to control for possible confounding variables, such as socioeconomic status. Our results show both positive and negative associations distributed across various regions of the brain. There are suggestions of positive correlations in anteromedial prefrontal areas and negative correlations in areas of orbital frontal and anterior cingulate, though they are modest. Possible evolutionary and methodological explanations for these results will be discussed.

Partial funding for this study was provided by the Alexis de Tocqueville Institution and Indiana University.

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