Evoked potential latency change with age suggests differential aging of primary somatosensory cortex.

The latencies of the first two cortical peaks in the somatosensory evoked potential were examined in subjects of various ages. Recent work on specialization of primary sensory cortex in primates implicates the cortical site of origin of the second cortical peak, P25, in the selective sensory losses of old age. The latency of the P25 peak changed significantly with age. The latency of the preceeding N20 peak, also of cortical origin but originating from a different site, showed no significant age-related change. Sex differences were present in both N20 and P25 latencies but were independent of the age effect in the latter. Our results provide electrophysiological evidence for differential aging of anatomically separate areas of somatosensory cortex.