[Changes in components of the auditory long-latency evoked potentials at different stages of the slow-wave sleep]

In accordance with the present views, during sleep, analysis of external stimuli continues at the subconscious level, because the need to estimate the biological significance of external stimuli in order to maintain a flexible contact of a sleeping subject with the environment persists during sleep. It is known that new components of the auditory evoked potentials (AEP) appear as sleep deepens. However, the common procedure of analysis of event-related potentials averaged for a group of subjects has some drawbacks because of the interindividual variability of the event-related potentials. Therefore, an additional analysis of the interindividual variability of the AEP shape and component structure can simplify the detection of individual components of group-averaged AEP at different stages of the slow-wave sleep. The AEPs were recorded in healthy volunteers (n = 26) during falling asleep in the evening from eight EEG derivations (F3, F4, C3, C4, P3, P4, O1, O2) in reference to a linked mastoid electrode. Computer-generated sound stimuli (50 ms-pulses with the frequency of 1000 Hz, 60 dB HL) were presented binaurally through earphones with interstimulus intervals of 20-40 s. Selective summation of AEPs for all the subjects was performed for each stage of the slow-wave sleep individually for each of the eight derivations. It was shown that the account made for interindividual variability of the AEP shape facilitated the identification of individual components of the group-averaged AEP typical of wakefulness (P1, N1, P300) and those which appeared during sleep onset and at different stages of the slow-wave sleep (P2, N350, P450, N550, N900).