The human secondary somatosensory cortex (S2) is a region of cerebral cortex lying mostly on the parietal operculum. Region S2 was first described by Adrian in 1940, who found that feeling in cats' feet was not only represented in the previously described primary somatosensory cortex (S1) but also in a second region adjacent to S1. In 1954, Penfield and Jasper evoked somatosensory sensations in human patients during neurosurgery using electrical stimulation in the lateral sulcus, which lies adjacent to S1, and their findings were confirmed in 1979 by Woolsey et al. using evoked potentials and electrical stimulation. Functional neuroimaging studies have found S2 activation in response to light touch, pain, visceral sensation, and tactile attention.