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 Niss1 stains plus immunohistochemical labeling with the SMI-32 antibody. The surface cortex between the IPS and central sulcus (overlapping area 2) was distinguished from surrounding cortex (areas 1 and 5) by relatively light SMI-32 immunoreactivity. This distinguishing architectonic feature was most evident between the post-central dimple and cortex immediately anterior to the tip of the IPS. Physiological mappings verified that the architectonic transition correlated with a change in receptive field properties, consistent with their marking the boundary between areas 2 and 5. These results suggest that area 2 occupies surface cortex anterior to the IPS, but not within the IPS.