[Reproducibility of somatosensory evoked potentials in normal humans]

The authors have applied the somatosensory evoked potentials (SEP) as an index of the brain function, and studied the reversibility of the ischemic brain dysfunction from the SEP changes under the drug-induced conditions. From the previous experiences, the authors are now doing the quantitative analysis of the amplitude of the early negative component (N1-amplitude) on SEP, and evaluating the reversibility of the brain dysfunction. The early components of SEP, including N1, were reported that responses were reasonably constant in normal subjects. Responses recorded at different times in the same subject were usually very similar and there were not significant differences among the responses recorded in different subjects. In the consecutive SEP recordings, however, the reproducibility of N1-amplitude has not yet fully studied. It is necessary to know the standard values when the significant changes of N1-amplitude are evaluated under the drug-induced conditions. The purpose of this paper is to study the reproducibility of N1-amplitude of SEP in the consecutive recordings, and also, stimulating and recording methods of SEP. Subjects were 15 normal volunteers, from 21 to 38 (mean: 29) years old. Two stimulating needle electrodes were inserted to the skin at the wrist, and the somatosensory stimulation was applied to the median nerve with 1 msec duration of square pulse. Monopolar EEGs were recorded from the scalp of the parietal region (P3 or P4) contralateral to the stimulation, and SEPs were recorded by averaging those EEGs with computer technique. N1-amplitude was determined by the vertical distance between peaks of P1 and N1 components.(ABSTRACT TRUNCATED AT 250 WORDS)