0169 Using serial awakenings to explore the spectral signature of sleep state misperception

Abstract

Abstract Introduction Sleep state misperception, or paradoxical insomnia, is a condition whereby an individual reports being awake even though polysomnographic evidence confirms they were asleep. Normally, an indication of sleep state misperception is determined by asking a patient to estimate the amount of wakefulness experienced after a full night of laboratory-monitored sleep. While clinically useful, this crude, post-hoc assessment does little to inform the neurobiological underpinnings of sleep state misperception. Here we used serial awakenings to exploit instances where a direct confirmation of sleep was followed by a subjective report of wakefulness. Methods 256 channel EEG with EMG, EOG and ECG was recorded in 19 primary insomnia (PI) subjects and 19 age- and sex-matched good sleeping controls (GSC) after a baseline sleep night ruled out comorbid disorders. After periods of stable sleep, participants were probed every 30 seconds with increasing intensity tones until a full awakening was achieved. Subjects were then asked to report whether they were awake or asleep before hearing the sound before going back to sleep. EEG data prior to the awakening was examined using multi-taper spectral analysis. Results Out of 464 serial awakenings (average 12 per subject, range 4-16), roughly 10% resulted in subjective wake reports during sleep (35 in NREM, 11 in REM; 24 in PI, 22 in GSC). Many of these occurrences included obvious arousals or other signs of wakefulness prior to the awakening tone. Altogether, 8 clean wake reports (4 in PI), occurred during stage N2 or N3 that could be matched with similarly clean data when the same subject reporting being asleep. Interestingly, spectral analysis of the 10 seconds prior to the awakening revealed significantly more alpha activity (9.1-11.3Hz paired t-test, p < .05) but no significant difference in slow wave activity. The alpha increase was localized to a mid-central region, similar to the alpha difference seen previously during deep sleep between PI and GSC groups, but also extended frontally. Conclusion Sleep state misperception may result from a localized increase in alpha activity while sleep persists. Serial awakenings are a useful tool for examining this paradoxical state. Support (If Any) Funded by the MERCK Sharp and Dohme Corporation.