Information processing in sleep based on event-related activities of the brain

Abstract

The study investigates information processing operations in rapid eye movement (REM) sleep and stages of non-REM sleep. An eclectic approach was used in the study whereby the effect of external auditory stimuli was investigated on both the peaks in the event-related potentials (ERP) waveform and on the oscillatory responses that contribute to the morphology of this waveform. Data on overnight sleep were acquired from 12 healthy, young adult, volunteer men; those on the awake stage were obtained from 21 matched men. Brain activity was obtained in response to auditory stimuli (2000 Hz deviant and 1000 Hz standard stimuli: 65 dB, 10 msec r/f time, 50 msec duration) under the passive oddball paradigm in sleep and the active and passive oddball paradigms in wakefulness. The effect of the experimental variables (stimulus type, sleep stage) on ERP peak amplitudes was studied through analysis of variance for repeated measures. The contribution of the oscillatory responses to the ERP peaks was studied using stepwise multiple regression. As represented with the amplitude of the ERP peaks and the oscillatory responses, auditory information processing selectively varied in different stages of sleep. Processing took longer in sleep: comparable peaks were obtained at longer latencies and later components appeared that did not exist in wakefulness. With a long-duration theta activity and greater differentiation between the deviant-and standard-elicited stimuli, Stage 2 appeared to represent effortful cognitive processing. As represented with only the earlier peaks and the insignificant delta activity, REM represented less extended cognitive processing.

Oscillatory responses representing differential auditory processing in sleep

“…In wakefulness, the delta response represents effortful cognitive processing (Başar, 1999;Başar-Eroğlu et al, 1992;Karakaş et al, 2000a,b;Parnejford and Başar, 1999;Schürmann et al, 1995) and contributes principally to P300 (Karakaş et al, 2000a,b). As a sign of delayed processing in sleep (Atienza and Cantero, 2001;Loewy et al, 1996;Karakaş et al, 2007), the delta oscillation contributed not to P3 but to the late negative N3 component of the present study. The maximum delay occurred in Stage 2 (676.44 ms).…”

“…Except for the two studies by Karakaş et al ( , 2007, the literature does not presently provide findings on the functional correlates of sleep oscillations (Feige et al, 1997;Röschke and Aldenhoff, 1991;Röschke et al, 1995). In their studies, Karakaş and colleagues based their arguments on ERP components in sleep, and oscillatory responses and ERP components in both sleep and wakefulness.…”

“…Compared to the theta response, the cognitive meaning of N1 has been more thoroughly studied in the literature. As in wakefulness (for review see Muller-Gass and Campbell, 2002;also Alcaini et al, 1994;Giard et al, 1994;Karakaş, 1997;Naatanen, 1992;Naatanen and Winkler, 1999;Woods, 1995), N100-P200 complex was induced in sleep by sensory stimulation of all types and was accordingly accepted to be an index of the presence (or absence) of sensory stimulation (Karakaş et al, 2007;Kevanishvili and Specht, 1979;Niiyama et al, 1996;Weitzman and Kremen, 1965); in other studies, it was considered as a representation of a general increase in sensory sensitivity associated with the arousal factor of the orienting response (Atienza et al, 2001a,b). The amplitude decrease throughout Stages 1, 2 and 4 was interpreted as the loss of attentional capacity with sleep (for review see Campbell and Colrain, 2002).…”

Analysis of non-REM sleep staging with electroencephalography bispectral index

“…The current results showed a significant correlation between non‐REM sleep stages and BIS values in the early sleep period. In light of the results from the present study and the few other existing studies, BIS or BIS‐like 15,29–32 assessments may become applicable for multi‐methodological study designs demanding higher temporal resolution and online assessment, which can further be applied to the psychophysiology 12 of the normal human brain under different states of consciousness, as well as pathological areas (neurology, psychiatry, anesthesia) and further studies on consciousness.…”

“…Recently, electrophysiological oscillatory results in the sleep environment have been presented 11–14 . The findings include the role of gamma oscillatory activity in sensory/perceptual processing and with respect to long‐duration theta activity, differentiation between the deviant‐ and standard‐elicited stimuli in sleep information processing.…”