[P300 and auditory information processing during natural sleep]. / P300 y procesamiento de información auditiva durante el sueño.

INTRODUCTION: The P300 is elicited, in the waking state and during an 'attention condition', in response to deviant stimuli of an oddball paradigm. This component of event related potentials (ERP) may be a useful research tool in the assessing of cortical sensory processing during normal sleep since a subject does not need to be awake or totally conscious in order to generate a measurable response. OBJECTIVE: This study used an classical oddball paradigm as a means to assess the auditory information processing during sleep. PATIENTS AND METHODS: The auditory ERP were registered in twelve healthy volunteers during the waking state and sleep stages II, III-IV and REM. The amplitude, latency and scalp distribution parameters of the positivity observed were contrasted with the results obtained in the waking state. RESULTS: A 'P300-like' with a significantly smaller peak amplitude and an increment of latency was elicited during stage II and the REM stage of sleep. As in the waking state, the positivity during this sleep stages was maximal at central-parietal regions. CONCLUSIONS: The response obtained seems to correspond both for the morphology of the potential as for the centro-parietal predominance with a waking P3b component. These results suggest that certain processes of attention and memory-related operations involved in the auditory processing of simple signals remain operative during these sleep stages.

[Subjective sleep quality and spectral analysis of electroencephalography during nocturnal sleep]. / Calidad subjetiva de sueño y análisis espectral del electroencefalograma de sueño nocturno.

INTRODUCTION: The relation between subjective sleep quality and the stages of polysomnography is unclear. Computerized sleep analysis provides a reliable tool for the study of sleep dynamics. OBJECTIVE: To study the relation between subjective sleep quality and spectral EEG parameters during nocturnal sleep. MATERIAL AND METHODS: Nocturnal sleep were recorded ambulatory in 26 subjects aged from 8 to 63. The following variables were extracted from EEG signal (Fz-Pz) quantified through the Fast Fourier Transformation (FFT): delta maximum, spectral peak, delta sleep time, efficiency and desynchronized sleep. A sleep diary was administered in the morning to assess the subjective sleep quality. Multiple regression and Anova were used for statistical analysis. RESULTS: Efficiency and delta maximum became significant predictors accounting for 54% of subjective sleep variance. The item 'how was your sleep?' was answered in a different way according to the delta maximum. CONCLUSIONS: Sleep depth, measured by spectral analysis, is an important predictor of the subjective sleep quality. The sleep classification in discrete stages ignores this feature.

Auditory event-related potentials to semantic priming during sleep.

The present study uses the N400 component of event-related potentials (ERPs) as a processing marker of single spoken words presented during sleep. Thirteen healthy volunteers participated in the study. The auditory ERPs were registered in response to a semantic priming paradigm made up of pairs of words (50% related, 50% unrelated) presented in the waking state and during sleep stages II, III-IV and REM. The amplitude, latency and scalp distribution parameters of the negativity observed during stage II and the REM stage were contrasted with the results obtained in the waking state. The 'N400-like' effect elicited in these stages of sleep showed a mean amplitude for pairs of unrelated words significantly greater than for related pairs and an increment of latency. These results suggest that during these sleep stages a semantic priming effect is maintained actively although the lexical processing time increases.

[Age as source of variation in various parameters of 'delta sleep']. / La edad como fuente de variación en algunos parámetros del 'sueño delta'.

INTRODUCTION: The clinic usefulness of a diagnostic test is in relationship to the precision with which measures the studied phenomenon. The lack of precision involve the reliability upon causing confounded results of the normal and diseased populations. OBJECTIVE: Since the sleep varies in function of the age, to find sleep parameters that fit better to the changes that the aging produces in the sleep. MATERIAL AND METHODS: Spectral analysis through the Fast Fourier Transformation of the ambulatory EEG of 28 healthy subjects. RESULTS: Maximum value of power (maximum depth) in a frequency of ended in a point of the sleep goes losing in a way specifies and systematical with the age. CONCLUSIONS: The variance accounted by this parameter is of the 87%, what, being tried to a phenomenon so variable as the sleep, supposes a interesting starting point to be applied to some pathologies in those which is presumed that the slow sleep (to which is attributed a paper in the cerebral restoration) is decreased.