Heritability in corpus callosum morphology and its association with tool use skill in chimpanzees (Pan troglodytes): Reproducibility in two genetically isolated populations

Abstract

The corpus callosum (CC) is the major white matter tract connecting the left and right cerebral hemispheres. It has been hypothesized that individual variation in CC morphology is negatively associated with forebrain volume (FBV) and this accounts for variation in behavioral and brain asymmetries as well as sex differences. To test this hypothesis, CC surface area and thickness as well as FBV was quantified in 221 chimpanzees with known pedigrees. CC surface area, thickness and FBV were significantly heritable and phenotypically associated with each other; however, no significant genetic association was found between FBV, CC surface area and thickness. The CC surface area and thickness measures were also found to be significantly heritable in both chimpanzee cohorts as were phenotypic associations with variation in asymmetries in tool use skill, suggesting that these findings are reproducible. Finally, significant phenotypic and genetic associations were found between hand use skill and region-specific variation in CC surface area and thickness. These findings suggest that common genes may underlie individual differences in chimpanzee tool use skill and interhemispheric connectivity as manifest by variation in surface area and thickness within the anterior region of the CC.

Distributed genetic effects of the corpus callosum subregions suggest links to neuropsychiatric disorders and related traits

“…This is in line with previous work which shows that the mid-posterior subregion is difficult to examine; perhaps due to its smaller size upon extraction, but to date there are no studies that have assessed its heritability in humans. Studies looking at its heritability in other primates suggest that it has a lower heritability when compared to larger subregions, such as the anterior subregion (Hopkins et al, 2022). Although we found no evidence to suggest a relationship between increasing subregion volume and the number of significant loci detected, this remains a possibility.…”

From fossils to mind

“…In many nonhuman primate species, for example, there is asymmetry in hand skill and preference related to the motor demands of different actions 93 . Behavioral lateralization in humans and nonhuman primates has been linked to hemispheric asymmetry in the anatomy of various brain regions, including the primary motor cortex and inferior frontal cortex 94,95 , as well as the morphology of the corpus callosum 96,97 . Indeed, it has been hypothesized that hemispheric specialization increased in hominins along with handedness, tool use and making, and language 90 .…”