Anatomical evidence for the posterior boundary of area 2 in the macaque monkey

This study examined the architectonic organization of the macaque's primary somatosensory cortex near the tip of the intraparietal sulcus (IPS), using myelin and Nissl stains plus immunohistochemical labeling with the SMI-32 antibody. The surface cortex between the IPS and central sulcus (overlappin g area 2) was distinguished from surrounding cortex (areas 1 and 5) by rela tively light SMI-32 immunoreactivity. This distinguishing architectonic fea ture was most evident between the post-central dimple and cortex immediatel y anterior to the tip of the IPS. Physiological mappings verified that the architectonic transition correlated with a change in receptive field proper ties, consistent with their marking the boundary between areas 2 and 5. The se results suggest that area 2 occupies surface cortex anterior to the IPS, but not within the IPS.