Central somatosensory conduction time from 10 to 79 years.

Somatosensory evoked potentials were recorded simultaneously from the neck and scalp following stimulation of the median nerve at the wrist in 83 normal subjects aged 10-79 years. The central somatosensory conduction time was measured by subtracting the peak latency of the major response from the upper cervical area (N14) from that of the primary cortical response (N20). The central conduction time remained constant between 10 and 49 years but increased abruptly by approximately 0.3 msec between the fifth and sixth decades. Following this increase there was no further change in the central conduction time. Changes with age in the amplitude of N14 and N20 differed both from the changes in latency and from each other. The amplitude of N14 was stable between 10 and 39 years but then declined progressively. The amplitude of N20 deceased between 10 and 39 years and then increased until the end of the seventh decade.