Somatosensory evoked potentials of the normal human neonate in REM sleep, in slow wave sleep and in waking.

Abstract Averaged cerebral potentials evoked by electrical stimulation of the fingers were investigated in thirty-four full-term normal human newborns. The stimuli were delivered at intervals of at least 3 sec and generally 5–12 sec to avoid sequential interactions between the responses. They were of adequate intensity to evoke consistent responses both at the contralateral parietal projection and at the vertex, but did not interfere with the normal cycles of Slow Wave Sleep (SWS) and of Rapid Eye Movement Sleep (REMS). The sleep stages were identified by a number of established criteria: pattern of respiration, eye, face and limb movements, spontaneous EEG, submental EMG and also by the histogram of heart beat intervals (Fig. 5, 8, 9, 11). The somatosensory evoked potentials present genuine and consistent features in typical REMS and SWS runs. The mean latency and voltage of the initial surface negative component, N 1 , which is characteristic of the newborn response but is no longer developed in the adult, do not differ significantly in the two sleep stages (Fig. 2, 3). The latency to the peak and the duration of N 1 are significantly increased in SWS (Fig. 4). The positive component P 1 which follows N 1 is recorded in both sleep stages. However, a second component P 2 is present only in SWS and it provides the most typical feature of that stage of sleep (Fig. 1, 5, 7, 9). As a result, the total duration of the positive deflection is much longer in SWS than in REMS (Fig. 4, E ). Late negative N 2 and positive P 3 components are also influenced by the sleep stages. Interesting correlations appear between the evoked potentials recorded at the hand projection and at the vertex (Fig. 9, 10). In waking the evoked potentials appear rather similar to those in activated REMS (Fig. 7, 8). The evoked somatosensory potentials in newborns permit a consistent analysis of both "primary" and late components of the cerebral responses and the sleep stages represent one of the major parameters to be considered in their investigation.