Study Objectives: The mismatch negativity (MMN) component of the event-rela
ted potentials reflects the automatic detection of sound change. Only a few
researchers have investigated the MMN elicitation during sleep in adult hu
man and some of them reported that MMN amplitude was decreased in sleep com
pared to in waking. However, it is not clear that the decrease of MMN ampli
tude was due to increased drowsiness or long-term response decrement. Two e
xperiments were conducted to clarify whether or not the MMN was elicited in
each sleep stage. We presented auditory stimuli to subjects continuously f
rom waking until sleep state (Experiment 1). Using the same experimental co
ndition, we examined whether or not MMN amplitude was influenced by long-te
rm stimulus presentation (80min.) and by vigilance level (Experiment 2).
Measurements & Results: Experiment 1. MMN was obtained in both drowsiness a
nd REM sleep. MMN was significantly smaller in amplitude and shorter in lat
ency in the both stages than in the waking state. However, MMN was not foun
d in another sleep stage. Experiment 2: Amplitudes were no different among
0-20 min., 20-40 min., 60-80 min. But it was decreased in 40-60 min. and po
wer value of alpha-wave was decreased in 40-60 min.
Conclusions: To obtain the reliable data, by using the automatic spectral a
nalysis, we confirmed that MMN was elicited in REM sleep. MMN was not influ
enced by long-term stimulation. The result suggested that auditory stimuli
could be processed in the preattentive sensory memory even in REM sleep.