Chimpanzee histology and functional brain imaging show that the paracingulate sulcus is not human-specific

The paracingulate sulcus -PCGS- has been considered for a long time to be specific to the human brain. Its presence/absence has been discussed in relation to interindividual variability of personality traits and cognitive abilities. Recently, a putative PCGS has been observed in chimpanzee brains. To demonstrate that this newly discovered sulcus is the homologue of the PCGS in the human brain, we analyzed cytoarchitectonic and resting-state functional magnetic resonance imaging data in chimpanzee brains which did or did not display a PCGS. The results show that the organization of the mid-cingulate cortex of the chimpanzee brain is comparable to that of the human brain, both cytoarchitectonically and in terms of functional connectivity with the lateral frontal cortex. These results demonstrate that the PCGS is not human-specific but is a shared feature of the primate brain since at least the last common ancestor to humans and great apes similar to 6 mya. The paracingulate sulcus (PCGS) is a brain structure long thought to be specific to humans, and variation in this structure has been linked to personality traits and cognitive abilities. In this study, Celine Amiez and Jerome Sallet et al. analyze brain imaging data from humans and chimpanzees to demonstrate that the PCGS is in fact present in our closest relative and its functional connectivity in chimpanzees is comparable to that in humans.