http://download.neurosky.com/docs/papers/bcq/Klimesch_1999_EEG_alpha_and_theta_oscillations_reflect_cognitive_and_memory_performance.pdf

EEG alpha and theta oscillations reflect cognitive and memory performance: a review and analysis

Sleep deprivation severely compromises the ability of human beings to respond to stimuli in a timely fashion. These deficits have been attributed in large part to failures of vigilant attention, which many theorists believe forms the bedrock of the other more complex components of cognition. One of the leading paradigms used as an assay of vigilant attention is the psychomotor vigilance test (PVT), a high signal-load reaction-time test that is extremely sensitive to sleep deprivation. Over the last twenty years, four dominant findings have emerged from the use of this paradigm. First, sleep deprivation results in an overall slowing of responses. Second, sleep deprivation increases the propensity of individuals to lapse for lengthy periods (>500ms), as well as make errors of commission. Third, sleep deprivation enhances the time-on-task effect within each test bout. Finally, PVT results during extended periods of wakefulness reveal the presence of interacting circadian and homeostatic sleep drives. A theme that links these findings is the interplay of “top-down” and “bottom-up” attention in producing the unstable and unpredictable patterns of behavior that are the hallmark of the sleep-deprived state.

Sleep Deprivation and Vigilant Attention

Premises of creation of Internet portal designed to provide access to participants of educational and scientific process for the joint creation, consolidation, concentration and rapid spreading of educational and scientific information resources in its own depository are considered. CMS-based portal content management systems’ potentiality is investigated. Architecture for Internet portal of MES of Ukraine’s information resources is offered.

Створення порталу інформаційно-довідкових ресурсів міністерства освіти і науки україни

Vigilance, alertness, or sustained attention: physiological basis and measurement.

Fundamental Statistics in Psychology and Education

Nine paid volunteers were sleep deprived over a period of 40 hours. Every 2 hours during total sleep deprivation (TSD) and after recovery sleep, oral temperature (OT), reaction time (RT) in a vigilance task and electroencephalogram (EEG) with eyes open and closed (C3, C4, T3 and T4) were recorded. Ten artifact-free samples from each condition were Fourier transformed. Absolute power was calculated for six bands. Analyses of variance with deprivation and time of day as factors showed the following significant results : 1) TSD induced an increase in RT, of theta power in all derivations, of beta power in both centrals and a decrease of alpha power with eyes closed ; OT was not affected. 2) All bands showed a peak of power at 1800 hours, 2 hours in advance of the OT acrophase at 2000 hours. All variables recovered baseline values after 1 night of sleep. Significant linear correlations of hours of wakefulness with EEG and RT, and of EEG power with OT and RT, were observed. The present findings show a linear increase in EEG power and RT with TSD, and a diurnal oscillation of EEG power, which is independent of TSD.

Effect of total sleep deprivation on reaction time and waking EEG activity in man

Nine young adult male (23-30 years old) paid volunteers were subjected to total sleep deprivation (TSD), after two consecutive nights in the laboratory, for 40 hours (from 0800 hours on the first day to 2400 hours on the following day). Oral temperature (OT), reaction time (RT) in a visual vigilance task, and electroencephalogram (EEG ; C3, C4, T3, and T4) while performing the task were recorded every 2 hours during TSD and after recovery sleep. One second of EEG, before target and non-target stimuli for every subject and condition was visually inspected, and artifact-free epochs were Fourier transformed. Absolute power (AP) was calculated for 4-20 Hz (full band) and for theta, alpha1, alpha2, and beta1. Analyses of variance (ANOVAs), with TSD and time-of-day as factors, showed the following significant results : TSD induced an increase in RT and AP of the full band at C3 and C4, of all bands at C3, of theta at T3, and of beta1 at T4 (p < 0.009 for all comparisons). No time-of-day effects nor interactions were found. OT was not affected by TSD. All variables returned to baseline values after recovery sleep. RT and EEG power showed a linear increase with accumulating hours of wakefulness. The increment in RT also correlated with the increase in EEG power. The results demonstrate that the increment in RT is associated with the increase in AP, particularly in the left central cortex ; that the EEG may be used to identify sleepiness ; and that EEG during task performance is more sensitive to TSD than during relaxed wakefulness.

Time course of reaction time and EEG while performing a vigilance task during total sleep deprivation.

12 sessions of EEG activity, one every second day, were recorded at F3, F4, C3, C4, P3, P4, O1 and O2 in 9 women with regular menstrual cycles. The following significant oscillations were observed: 1) absolute power was lower during periovulatory period; 2) absolute power of delta theta and alpha1 was higher during premenstrual period whereas absolute power of alpha2, betal and beta2 was higher during menstruation; 3) relative power of low alpha frequencies was lower and that of high frequencies was higher during premenstrual period; 4) interhemispheric correlation between frontals was higher during ovulation and between occipitals was higher during premenstrual phase; 5) no significant power asymmetries were observed. The present findings suggest higher activation of centro-parietal regions during menstruation and lower activation of frontal regions during premenstrual phase.

EEG oscillations during menstrual cycle.

EEG activity of 16 adult volunteers. 8 male and 8 females was monopolarly recorded at P3 and P4 at rest and during solution of three series of tasks: one analytic, one spatial and one mixed demanding both kinds of processing. The following main effects were observed: Men showed significantly higher beta relative power than women, while women showed significantly higher alpha relative power than men during all conditions. Alpha relative power decreased, while theta relative power increased during tasks solution in both sexes. Beta relative power was significantly higher at the left parietal only in men. Interparietal correlation was significantly higher in women than in men during all conditions and bands. For the theta band it increased from baseline values during tasks solution in men, while in women it decreased during the analytic task.

Gender differences in the EEG during cognitive activity.

Correlation patterns between the electroencephalographic activity of both hemispheres in adult subjects were obtained. The morphology of these patterns for one subject was compared with another subject's patterns during control situations without communication, and during sessions in which direct communication was stimulated. Neither verbalization nor visual or physical contact are necessary for direct communication to occur. The interhemispheric correlation patterns for each subject were observed to become similar during the communication sessions as compared to the control situations. These effects are not due to nonspecific factors such as habituation or fatigue. The results support the syntergic theory proposed by one of the authors (Grinberg-Zylberbaum).

J. Ramos

Papers

Effect of total sleep deprivation on reaction time and waking EEG activity in man

Time course of reaction time and EEG while performing a vigilance task during total sleep deprivation.

EEG oscillations during menstrual cycle.

Gender differences in the EEG during cognitive activity.

Patterns of interhemispheric correlation during human communication.