Organization of face representation in the cingulate cortex of the rhesus monkey.

Neuroanatomical and electrophysiological methods were used to investigate the organization of face representation in the cingulate gyrus of four rhesus monkeys. Injections of fluorescent tracers placed into electrophysiologically defined sectors of the primary (M1) and supplementary (M2) motor cortices demonstrated that the rostral part of area 24c and the rostral part of area 23c send projections to the face representations of M1 and M2. Injections of biotinylated dextran amine involving the rostral part of area 24c and rostral part of area 23c demonstrated a direct projection from both areas to the facial nucleus of the pons. Our data suggest that areas 24c (M3) and 23c (M4) each contain a face representation which directly affects cortical as well as subcortical neural centers controlling facial activity.