Abstract
We aimed at better understanding the brain mechanisms involved in the processing of alerting meaningful sounds during sleep, investigating alpha activity. During EEG acquisition, subjects were presented with a passive auditory oddball paradigm including rare complex sounds called Novels (the own first name - OWN, and an unfamiliar first name - OTHER) while they were watching a silent movie in the evening or sleeping at night. During the experimental night, the subjects’ quality of sleep was generally preserved. During wakefulness, the decrease in alpha power (8–12 Hz) induced by Novels was significantly larger for OWN than for OTHER at parietal electrodes, between 600 and 900 ms after stimulus onset. Conversely, during REM sleep, Novels induced an increase in alpha power (from 0 to 1200 ms at all electrodes), significantly larger for OWN than for OTHER at several parietal electrodes between 700 and 1200 ms after stimulus onset. These results show that complex sounds have a different effect on the alpha power during wakefulness (decrease) and during REM sleep (increase) and that OWN induce a specific effect in these two states. The increased alpha power induced by Novels during REM sleep may 1) correspond to a short and transient increase in arousal; in this case, our study provides an objective measure of the greater arousing power of OWN over OTHER, 2) indicate a cortical inhibition associated with sleep protection. These results suggest that alpha modulation could participate in the selection of stimuli to be further processed during sleep.
Highlights
Sleep and wakefulness are two physiological states accompanied by different levels of consciousness
Components like the N1 elicited by pure tones [6], the MMN elicited by deviant pure tones [3], the P300 elicited by the own first name presented among other first names [7], the P3a, elicited by deviant pure tones [3], the N400 elicited by semantically incongruent pairs of words [8], were found to be maintained but modified during sleep
Our study shows that complex sounds have a different effect on the alpha power during wakefulness and during REM sleep
Summary
Sleep and wakefulness are two physiological states accompanied by different levels of consciousness. Components like the N1 elicited by pure tones (marker of lowlevel auditory processing) [6], the MMN elicited by deviant pure tones (marker of sensory memory) [3], the P300 elicited by the own first name presented among other first names (marker of word discrimination) [7], the P3a, elicited by deviant pure tones (marker of attention orienting) [3], the N400 elicited by semantically incongruent pairs of words (marker of semantic processing) [8], were found to be maintained but modified during sleep These studies strongly argued in favor of the maintenance of perceptive and complex cognitive processes during sleep. Adrian (1937) cited by Brain (1958) [9] and Formby (1967) [10] showed that a young mother is more awaken by her infant’s screams than by other sounds or other baby cries These behavioral and electrophysiological data suggest that the sleeping brain can filter auditory information so that only alerting and/or significant stimuli reach higher-level processing
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