The Neurophysiological Basis of the Discrepancy between Objective and Subjective Sleep during the Sleep Onset Period: an EEG-fMRI study.

Sleep. 2018 Mar 24;:

Authors: Hsiao FC, Tsai PJ, Lane TJ, Wu CW, Lee HC, Chen LC, Lee WK, Lu LH, Wu YZ, Yang CM

Abstract
Subjective perception of sleep is not necessarily consistent with EEG indications of sleep. The mismatch between subjective reports and objective measures is often referred to as "sleep state misperception" (SSM). Previous studies evince that this mismatch is found in both insomnia patients and in normal sleepers, but the neurophysiological mechanism remains unclear. The aim of the study is to explore the neurophysiological basis of this mechanism, from the perspective of both EEG power and fMRI fluctuations. Thirty-six healthy young adults participated in the study. Simultaneous EEG and fMRI recordings were conducted while the participants were trying to fall asleep in an MRI scanner at approximately 9:00 PM. They were awakened after achieving stable N1 or N2 sleep, or after 90 minutes without falling into stable sleep. Next they were asked to recall their conscious experiences from the moment immediately prior to awakening. Sixty-one instances of scheduled awakenings were collected: twenty-nine of these after having achieved stable stage N2 sleep; twelve, during stage N1 sleep; and, twenty during the waking state. Relative to those awakenings without subjecitve-objective discrepancy, these awakenings with discrepancy were associated with lower theta power, as well as higher alpha, beta, and gamma power. Moroever, we found that participants who exhibited the discrepancy, compared to those who did not, evinced a higher amplitude of low-frequency fluctuation (ALFF) levels in the prefrontal cortex. These results lend support to the conjecture that the subjective-objectve discrepancy is associated with CNS hyperarousal.

PMID: 29590443 [PubMed - as supplied by publisher]