Initiation of Joint Attention is Associated with Morphometric Variation in the Anterior Cingulate Cortex of Chimpanzees (Pan troglodytes)

摘要

In developing human children, joint attention is an important preverbal skill fundamental to the development of language. Poor joint attention skills have been described as a behavioral risk factor for some neurodevelopmental disorders, such as autism spectrum disorder. It has been hypothesized that the anterior cingulate cortex (ACC) plays an important role in the development of joint attention in human children. Here, we tested whether the morphometry and lateralization of the ACC differed between chimpanzees that were classified as either consistently or inconsistently engaging in joint attention with a human experimenter. Results showed that chimpanzees that performed poorly on the joint attention task had larger grey matter volumes in the ACC compared to apes that performed well on the task. In addition, both population-level asymmetries and sex differences in the volume of GM were found within the ACC. Specifically, females had relatively larger GM volumes in two of the three subregions of the ACC compared to males, and significant leftward asymmetries were found for two of the subregions whereas a rightward biases was observed in the third. Based on these findings, we suggest that the ACC plays in important role in mediating joint attention, not just in humans, but also chimpanzees. We further suggest that the differences found between groups may reflect inherent differences in the amount of white matter within the ACC, thereby suggesting reduced connectivity between the ACC and other cortical regions in chimpanzees with poor joint attention skills.