Association between precentral gyrus morphology and modality-specific intentional communication in chimpanzees ( <i>Pan troglodytes</i> )

The precentral gyrus (preCG) is morphologically defined posteriorly by the central sulcus (CS) and anteriorly by the superior and inferior precentral sulci (preCS). Stimulation of the preCG along the dorsal-ventral plane elicits motor activation across the body in a topographic manner. In this study, we used postimage analyses to characterize the shape of the CS and preCS in a sample of 278 magnetic resonance image scans of chimpanzees. Using these data, we initially described the six most prominent preCG shapes variants, their asymmetries, and heritability. We also tested for their association with selective use of attention-getting communicative behaviors produced in the vocal and manual modalities. Associations were observed between preCG variants and vocal, but not manual, communication. Vocal communication was significantly associated with the inferior preCG shape in the left hemisphere. In contrast, no association was found in CS variants. We also found modest heritability in three of the preCG shape patterns but no significant genetic correlation with vocal intentional communication. Our results suggest that better selective use of a vocal attention-getting sound used for intentional communication is associated with a unique morphological landmark within the inferior preCG.