EEG changes associated with subjective under- and overestimation of sleep duration.

: Feeling awake although sleep recordings indicate clear-cut sleep occurs sometimes in good sleepers and to an extreme degree in patients with so-called paradoxical insomnia. It is unknown what underlies sleep misperception, as standard polysomnographic (PSG) parameters are often normal in these cases. Here we asked whether regional spectral power changes could account for the mismatch between objective and subjective total sleep times (TST). To set cutoffs and define the norm, we first evaluated sleep perception in a population-based sample, consisting of 2092 individuals who underwent a full PSG at home and estimated TST the next day. We then compared participants with a low mismatch (normoestimators, n=1147, ±0.5 SD of mean) with those who severely underestimated (n=52, 97.5th percentile). Compared to normoestimators, underestimators displayed increased EEG activation (beta/delta power ratio) in both REM and NREM sleep, while overestimators showed decreased EEG activation (significant in REM sleep). To spatially map these changes, we performed a second experiment, in which 24 healthy subjects (HS) and 10 insomnia patients underwent high-density sleep EEG recordings. Similarly to underestimators, patients displayed increased EEG activation during NREM sleep, which we localized to central-posterior brain areas. Our results indicate that a relative shift from low- to high-frequency spectral power in central-posterior brain regions, not readily apparent in conventional PSG parameters, is associated with underestimation of sleep duration. This challenges the concept of sleep misperception, and suggests that instead of misperceiving sleep, insomnia patients may correctly perceive subtle shifts towards wake-like brain activity.