ACTIVATION OF HUMAN MESIAL CORTEX DURING SOMATOSENSORY TARGET DETECTION TASK

We recorded somatosensory evoked fields (SEFs) from 10 healthy subject s to ulnar and median nerve stimuli presented at random intervals of 2 .4-21.6 s. The subjects either counted the stimuli or ignored them by reading a book. The stimuli activated in both conditions the contralat eral SI cortex, the ipsi- and contralateral SII cortices, and the post erior parietal cortex (PPC), in line with earlier observations. In add ition, a novel response was observed in nine subjects at 120-160 ms. I t was clearly enhanced by attention and was generated in the mesial co rtex of the paracentral lobule, close to the end of the central sulcus .