Corpus Callosum Morphology in Capuchin Monkeys Is Influenced by Sex and Handedness

Abstract

Sex differences have been reported in both overall corpus callosum area and its regional subdivisions in humans. Some have suggested this reflects a unique adaptation in humans, as similar sex differences in corpus callosum morphology have not been reported in any other species of primate examined to date. Furthermore, an association between various measurements of corpus callosum morphology and handedness has been found in humans and chimpanzees. In the current study, we report measurements of corpus callosum cross-sectional area from midsagittal MR images collected in vivo from 14 adult capuchin monkeys, 9 of which were also characterized for hand preference on a coordinated bimanual task. Adult females were found to have a significantly larger corpus callosum: brain volume ratio, rostral body, posterior midbody, isthmus, and splenium than adult males. Left-handed individuals had a larger relative overall corpus callosum area than did right-handed individuals. Additionally, a significant sex and handedness interaction was found for anterior midbody, with right-handed males having a significantly smaller area than right-handed females. These results suggest that sex and handedness influences on corpus callosum morphology are not restricted to Homo sapiens.

Prey capture efficiency in brown capuchin monkeys (Cebus apella) is influenced by sex and corpus callosum morphology

“…Previous research has found significant sex differences in male and female capuchins [Phillips et al, 2007], with males having smaller CC:brain ratios than females and smaller splenia than females. These sex differences were also found in our sample.…”

“…CC area measurements were taken from the midsagittal slice using a method similar to that described by Sanchez et al [1998] and others [Phillips et al, 2007[Phillips et al, , 2009Pierre et al, 2008] in non-human primates. The method divides the CC into five segments which are roughly associated with different sets of fiber projections to various cortical regions of the brain [Pandya et al, 1971;Witelson, 1989] (Fig.…”

“…Whereas behavioral data supporting this hypothesis is limited (and controversial), Schoenemann [2006] reported that women with smaller splenia scored better on a task of spatial-ability than women with larger splenia. Given that capuchins display sex differences in the CC morphology, including regions involved in the spatialability (splenium) [Phillips et al, 2007], we investigated the functional significance of these morphological differences using a task of visuospatial ability-prey capture. We hypothesized that male capuchins would be more efficient at prey capture than females, and concomitantly males would have smaller splenia than females.…”

Hand preference in fast-moving versus slow-moving actions in capuchin, Sapajus spp., and squirrel monkeys, Saimiri sciureus

“…Hellner-Burris et al (2010) suggested a relationship among prey capture, the degree of lateralization and the morphology of the corpus callosum in capuchin monkeys, and our findings suggest that this set of related asymmetries may have an adaptive explanation. However, the neurobiological bases of hand preference remain unresolved (Phillips & Hopkins, 2007), even though manual laterality in capuchins and chimpanzees seem to be linked to brain asymmetries (Dunham & Hopkins, 2006;Hopkins & Cantalupo, 2004;Hopkins, Cantalupo, & Taglialatela, 2007;Phillips & Hopkins, 2007;Phillips & Sherwood, 2005;Phillips, Sherwood, & Lilak, 2007).…”

Sylvian fissure asymmetry in capuchin monkeys (Cebus apella)

“…Capuchin monkeys are largebrained, socially complex primates with a rich vocal repertoire (Di Bitetti, 2003Gros-Louis, 2004;Jack, 2007;Rilling & Insel, 1999). Given these characteristics and recent findings of neuroanatomical asymmetries and their relationship to lateralised behaviour in capuchins (Phillips & Hopkins, 2007;Phillips & Sherwood, 2005;Phillips, Sherwood, & Lilak, 2007), it was hypothesised that they would display leftward asymmetry of the SF. While Hopkins et al (2000) reported leftward asymmetry in the medial region of New World monkeys, their sample only consisted of four capuchin monkeys and four squirrel monkeys (Saimiri sciureus), and analyses pooled both species.…”