The Ventral Premotor Cortex, Corticospinal Region C, and the Origin of Primates

In addition to its projection to the brainstem, the ventral premotor cortex (PMv) sends axons directly to the upper cervical spinal cord in primates, with few terminations more caudally in either the cervical enlargement or in the lumbosacral spinal segments. This finding suggests that PMv plays a role in the control of head movements. Furthermore, comparative neuroanatomical studies indicate that PMv's corticospinal projection was a primate innovation. If the first primates adapted to an arboreal life that involved unimanual feeding, as some experts believe, then perhaps PMv's corticospinal projection evolved to coordinate head movements with this kind of feeding behavior. The computations underlying such control could later be adapted to control head orientation during social signaling.