The recovery cycle of the averaged auditory evoked response during sleep in normal children

Abstract

1. 1. The recovery cycle of the averaged auditory evoked response (AER) to paired clicks was studied during Stage 2 and REM sleep in 23 normal 22–67-month-old children. Stimulus separations of 250, 160, 80, 40, 20 and 10 msec were used. The paired clicks were alternated with single clicks every 2.0 sec througout the night. The amplitude and latency of wave N 2 of the averaged response to the second click of each pair was measured after subtraction of the overlapping components of the averaged response to the first click. 2. 2. the 50% or greater attenuation of amplitude recovery reported for the waking state with stimulus separations of 500 msec was not obtained during sleep until stimulus separations shorter than 40 msec were used. 3. 3. In Stage 2 sleep, significant reduction of amplitude recovery occurred at stimulus separations of 250 and 20 msec. During REM sleep, there was significant reduction of amplitude recovery at all stimulus separations. The reduction of amplitude recovery was significantly greater during REM sleep than during Stage 2 sleep at stimulus separations equal to and shorter than 80 msec. However, the amplitude recovery cycle in the two sleep stages was similar, with lows of relative suppression at 250 msec and 40-20 msec separated by a peak of relative facilitation at 160-80 msec. The amplitude recovery cycle was best described by a combination of linear and cubic components. 4. 4. In Stage 2 sleep, the only significant effect on latency recovery was a slight delay at an 80 msec stimulus separation. During REM sleep, significant delays in recovery occurred at 80, 40 and 20 msec. There were no significant differences in latency recovery between the two sleep stages at any stimulus separation. The latency recovery cycle showed a significant linear delay in recovery with shorter stimulus separations in both sleep stages. In Stage 2 sleep a cubic component was also required to describe the latency recovery cycle while in REM sleep there was also a strong quadratic component. 5. 5. Within the age range of the subjects, significant age-related effects were limited to increased amplitude recovery and delay in recovery during REM sleep at a 250 msec stimulus separation with increasing age.