• Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In order to establish validity of an objective scale of alertness-sleepiness, one is forced to somehow calibrate it using subjective scales, such as the Karolinska Sleepiness Scale (KSS). We evaluated the effects of prolonged wakefulness on the extent of disagreement between objective and subjective KSS assessments, and tested whether calibration of an objective alertness-sleepiness scale can be established in despite of the limited reliability of subjective reports. Starting from 7p.m., the resting electroencephalogram (EEG) was recorded with 2-hour interval over the last 32-50 hours of 44-61-hour wakefulness of 15 healthy study participants. Frontal and occipital scores on the 2nd principal component of the EEG spectrum and occipital alpha-theta power difference were computed for one-min intervals of 5-min eyes-closed EEG recordings. To obtain alertness scale's scores in the range from 5 to 0, positive and negative values of these EEG indexes were assigned to 1 and 0, respectively, and then summed. Although correlation between time courses of objective and subjective (KSS) scores was very strong, evidence for systematic errors in both the mean and the calibration was also found. Correction of these errors resulted in strengthening of correlation (r=0.99) and establishing one-to-one correspondence between the steps of objective and subjective scales. The results indicate that scores from 5 to 0 on the objective alertness scale can be anchored to minimal, mild, moderate, marked, severe, and disabling levels of sleepiness.
    International journal of psychophysiology: official journal of the International Organization of Psychophysiology 08/2014; DOI:10.1016/j.ijpsycho.2014.07.010 · 2.65 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Attenuation of alpha rhythm in occipital derivation serves as a reliable electroencephalographic (EEG) marker of sleep onset. If such attenuation not only coincides with but also anticipates sleep onset, objective evaluation of sleepiness of permanently waking individuals might be facilitated by probing alpha attenuation right after eyes closing. We tested whether alpha-based EEG indexes reflect self-scored sleepiness and objectively measured waking ability. Fifteen young adults self-scored their sleepiness before and after recording of their resting EEG with a 2-hour interval in the course of 43-61-hour wakefulness. For each EEG record, power spectra were calculated on two-minute interval of eyes open section and on 5 following one-minute intervals of eyes closed section. Waking ability was assessed as latency to sleep onset marked by zero-crossing decline of such EEG indexes as alpha-theta power difference in occipital derivation and scores on the 2nd principal component of the EEG spectrum in frontal and occipital derivations. Alpha attenuation during the first minute with eyes closed was found to be significantly related to the levels of subjective sleepiness and waking ability. The relationship between alpha attenuation and subjective sleepiness was confirmed by analyzing one-minute eyes closed EEG recordings obtained with a 3-hour interval in the course of 24-hour sustained wakefulness of 130 adolescents and adults. We concluded that such one-minute eyes closed EEG recordings might be used for simple and quick measurements of sleepiness and waking ability in experimental and field studies of permanently waking individuals.This article is protected by copyright. All rights reserved.
    Clinical and Experimental Pharmacology and Physiology 09/2014; 41(12). DOI:10.1111/1440-1681.12311 · 2.41 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose Quantitative EEG measurement of sleepiness must be regarded both as fundamentally and practically important. In a search for the markers of physiological sleepiness, we tested whether the time course of self-perceived sleepiness/alertness correlates with the time courses of scores on principal components of the EEG spectrum. Subjects and methods The resting EEG was recorded in 15 healthy subjects with 2 h intervals in frontal and occipital derivations for the last 32–50 h of 44–61 h wakefulness. The correlation coefficients were calculated to test associations of the time course of self-perceived sleepiness/alertness with the time courses of spectral powers and scores on the two largest principal components of the EEG spectrum. Results and conclusion The results demonstrate that objective markers of sleepiness can be derived by means of principal component analysis of the EEG spectrum. A score on the 2nd principal component appears to be the most reliable correlate of sleepiness, because it exhibits the fastest decline at the boundary between wakefulness and sleep. A score on the 1st principal component was characterized by a decline before sleep onset followed by a rapid rise after it. These two scores were interpreted as the pure representatives of the wake and sleep drives, respectively, while spectral powers in separate frequency bands appear to reflect simultaneous influences of both drives.
    Somnologie - Schlafforschung und Schlafmedizin 06/2012; 16(2). DOI:10.1007/s11818-012-0561-1

Full-text (2 Sources)

Download
31 Downloads
Available from
Jun 3, 2014