Observer-independent characterization of sulcal landmarks and depth asymmetry in the central sulcus of the chimpanzee brain.

The central sulcus (CS) divides primary motor and sensory cortex in many mammalian brains. Recent studies have shown that experiential factors can influence the volume and lateralization of the CS in both human and nonhuman primates. In this study, we sought to define specific landmarks and the depth of the CS region corresponding to the motor-hand area of chimpanzees for comparison with humans using a novel, observer independent method applied to sample of 32 magnetic resonance images (MRI) scans. Our results showed that the dorsal-ventral location of the motor-hand region is comparable between humans and chimpanzees, though the depth of the CS was significantly greater in humans compared to chimpanzees. We further found that CS area corresponding to the motor-hand area was significantly larger in the hemisphere contralateral to the chimpanzees preferred hand. The methods employed here offer some potential advantages over traditional region-of-interest in the comparative study of cortical organization and gyrification in primates and are discussed.