The corpus callosum in nonhuman primates. Determinants of size.

The relationships between brain weight, sex and various callosal parameters including cross-sectional surface area and maximum splenial width in nonhuman primates are delineated. Overall, brain weight is a good predictor of quantitative aspects of the corpus callosum. However, both pongids and strepsirhines evince sex differences on certain callosal measures. No sex differences were found for either the ceboids or cercopithecoids. We speculate that one aspect of primate brain evolution has involved the modulation of interhemispheric connectivity along the lines of sex.