[Somatosensory cortical evoked potentials in normal subjects to single and double median nerve stimulation (author's...

On the wrist the median nerve of 42 normal subjects was stimulated by single and double stimuli and the contralateral cortical evoked potentials (SRAP) were evaluated with regard to peak-latencies, amplitudes and refractory period. SRAP after single nerve stimulations has 4-6 peaks in the first 100 ms, in 19 of 42 subjects there is an early peak ("peak 14-15") of the brain stem. The peak-latencies of minimum 1, maximum 1 and minimum 2 increase with the age not significantly. There are no right/left differences of the SRAP-amplitudes or -latencies. The duration of the relative refractory period was determined through the lengthening of latency respectively through the loss of minimum 1. The relative refractory time is independent of age, the absolute refractory time increase with advanced age. The refractory times of the first 4 peaks are not different for the right and left hemisphere. A slow alpha-rhythm correlate significantly with a higher absolute refractory time.