‘Oddballʹ event-related potentials and information processing during REM and non-REM sleep

Auditory stimuli consisting of the subjectʹs own name and an irrelevant word, counterbalanced in probabilities, were presented to 15 male subjects in the awake state and during natural sleep. Potentials recorded to these stimuli, as well as to clicks presented during sleep in a preceding night, were recorded and compared. Principal component analysis (PCA) was conducted on evoked potentials to distinguish temporally overlapping components, and ANOVA was applied on the eigenvector coefficients. During non-REM sleep a parietal P450, more prominent in stage 2, was observed in addition to the prominent waveform of a K-complex, which was also recorded in response to clicks and consisted of N350, N550 and P1000. During REM sleep, a fronto-central negativity which resembled non-REM N350, a parietal positivity at about 450 ms and a large N700 were detected. ANOVA on PCA coefficients showed a significant effect of verbal-stimulus type (name/irrelevant) on an eigenvector, which included all the components observed during stage 2 sleep. Coefficients during REM sleep showed a significant effect of stimulus probability on an eigenvector consisting of a prominent P450, suggesting a resemblance to the awake P300 component. This could not be demonstrated during non-REM sleep. The results indicate continued evaluation of auditory input salience during sleep, which diminishes during deep sleep, and is replaced by evaluation of stimulus context in a train of stimuli during REM sleep.