2021 Volume 39 Issue 1 Pages 65-78
The exact functions of the K-complex are under investigation; however, the K-complex, unique to Stage 2 sleep, reportedly plays a role in arousal induction and sleep protection. Event-related potentials (ERPs),appearing when externally evoked K-complexes are observed, have a monomodal (N300-P900 or N550-P900) or a bimodal (N300-P400-N550-P900) morphology. Studies have indicated the involvement of P400 in these morphological differences. P400 reflects information processing about external stimuli, which decays or disappears as sleep-depth increases. We compared the ERP waveforms and the functions of auditory evoked K-complex by dividing Stage 2 sleep of the first sleep cycle into first and second half sections. Results indicated that P400 amplitude attenuated in the second compared to the first half. Concomitantly, we observed a bimodal (N300-P400-N550-P900) ERP waveform in the first half, whereas a monomodal (N300-P900) waveform was observed in the second half of the first sleep cycle. These findings suggest that the function of the K-complex in the first half of Stage 2 sleep might predominantly be arousal induction, whereas its function in the second half is sleep protection.
