THE MISMATCH NEGATIVITY TO FREQUENCY DEVIANT STIMULI DURING NATURAL SLEEP

Eight subjects spent a single night in the sleep laboratory. Event-rel ated potentials (ERPs) were recorded during the presentation of two au ditory 'oddball' stimulus conditions in which tonal frequency was mani pulated. In the first condition, 1000 Hz 'standard' and 2000 Hz 'devia nt' tones were presented. In the second condition, the deviant tone wa s reduced to 1050 Hz. In both conditions, deviant probability was 0.2. Stimuli were presented every 600 ms during wakefulness and stages 2, 4, and REM of sleep. A distinctive N1 wave was visible in both stimulu s conditions when the subject was awake. The deviant stimuli elicited a 'mismatch negativity' (MMN) that inverted in polarity at the mastoid . In REM sleep, an N1 and a MMN were also elicited in both conditions. In the large deviance condition, the MMN had a slightly attenuated am plitude and was shorter in duration while in the small deviant conditi on, its peak latency was unusually early. Neither the N1 nor the MMN c ould be recorded in non-REM sleep.