Electroencephalographic and Electromyographic Events During Spontaneous and Final Arousal from Sleep: Study of the Sequence of Appearance and Significance

Objective Though there are excellent reviews on the functional significance of spontaneous arousals during sleep, associated electroencephalographic (EEG) and electromyographic (EMG) changes need further studies. Moreover, a comparison of these changes with early morning arousal from sleep will help in improving our understanding of sleep–wake regulations. Methods The study conducted on 15 healthy young volunteers showed that the spontaneous arousals, with associated EEG and EMG changes, occurred almost uniformly throughout non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. Results EEG changes preceded EMG changes in majority of the events. There was a delay of more than a second in between EEG and EMG changes, in both spontaneous arousals and early morning awakenings. Compared to the pre-arousal values, there was a significant increase in the delta power and all the frequency bands during spontaneous arousals. Though similar changes in EEG happened during the early morning awakenings, there were significant differences in beta and sigma EEG powers and computed root mean square EMG during the early morning awakenings. Conclusion The differences in the characteristic features of EEG and EMG changes during spontaneous arousal and early morning arousal indicated the probable role of these changes in facilitating the continuance of sleep in the former, and waking up from sleep in the case of the latter.