Representation of the body surface in somatic koniocortex in the prosimian Galago.

Microelectrode mapping methods were used to determine the organization of somatosensory cortex in galagos, a prosimian primate. A systematic representation of the controlateral body surface was found within somatic koniocortex with an organization comparable to that of Area 3b of parietal cortex of monkeys (S-I proper) and primary somatosensory cortex (S-I) of other mammals. Limited studies of the response properties of single neurons within the representation revealed further similarities with the 3b field of monkeys. We conclude that somatic koniocortex of galagos and Area 3b of monkeys are homologous, and suggest the term S-I proper for the representation in both prosimians and monkeys. Differences in the details of S-I proper in galagos and monkeys suggest a more primitive organization in galagos.