Topographical spectral power changes associated with NREM parasomnia episodes - a high-density EEG study.

Objectives/Introduction: Arousal disorders are NREM parasomnias characterized by incomplete awakenings from slow wave sleep (SWS) and abnormal behavior. Previous work suggested that parasomnia episodes (PE) display features of both sleep and wake in different brain areas. However, these observations are based on single episodes/patients and techniques that are not widely available (SPECT, intracranial recordings). Here we asked whether we could identify consistent changes in brain activity associated with PE using high-density (hd)-EEG. Methods: Six subjects (4F, age 24.3 ± 5.3, 18-33) presenting NREM parasomnia episodes (sleepwalking, confusional arousals or night terrors) at least 1×/week underwent a baseline and a second sleep recording after 24 h total sleep deprivation (hd-EEG with 256 electrodes). During the latter, acoustic stimulations were administered to provoke PE. Selected EEG segments corresponding to PE were cleaned from artifacts using independent component analysis. Channels with artifacts were removed and interpolated. Topographical spectral power (2-35 Hz) of PE was compared with SWS (60 s preceding each episode) and daytime wakefulness (20 s with eyes open) using paired t-tests. A cluster- and probability based correction for multiple comparisons was applied. Results: 26 clear-cut PE in 6 subjects were recorded (confusional arousals and night terrors). Compared to SWS, PE were characterized by significantly lower delta (2-4 Hz) and higher beta power (18-30 Hz) in a centro-frontal region (p < 0.05). With respect to wakefulness, this area showed significantly increased delta activity during PE (p < 0.05). Alpha power was also significantly increased in temporal regions (p < 0.05) during PE. No significant differences were found for other frequency bands. Conclusions: Our results suggest that it is possible to use hd-EEG recordings to study regional brain activity during behavioral episodes. EEG during episodes displays both features of wake (increased high-frequency activity with respect to sleep) and sleep (increased low-frequency activity with respect to wake). The most consistent changes were restricted to a circumscribed fronto-central brain region, which is known to receive major projections from arousal-related structures.