EEG characteristics prior to and following the evoked K-Complex.

This study was designed to determine if the K-Complex reflects an arousal from sleep or a sleep protection mechanism. Ten participants were presented auditory stimuli every 20 s while asleep. Trials were sorted according to the presence or absence of a K-Complex. A fast Fourier Transformation of the data was computed on EEG segments prior to and following stimulus onset. The log power of activity in delta, theta, alpha, sigma, and beta bandwidths was computed. When a K-Complex was elicited, there were no differences in EEG activity prior to and following the stimulus. However, during slow wave sleep, when a K-Complex was not elicited, there was a significant overall increase in theta, alpha, sigma, and beta activity following stimulus. These results tend to support the notion that the K-Complex appears to prevent arousal.