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Subjective Alertness (subjective + alertness)
Selected AbstractsThe effects of caffeine on simulated driving, subjective alertness and sustained attentionHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 7 2001Carolyn Brice Abstract There is evidence that caffeine increases alertness and reduces fatigue. This may be especially so in low arousal situations (e.g. working at night or for prolonged hours). Caffeine has also been found to improve performance on vigilance tasks and simple tasks requiring sustained response. Again, these effects are often clearest when alertness is reduced, although there is evidence that benefits may still occur when the individual is unimpaired. Most studies to date have investigated the behavioural effects of caffeine in laboratory experiments using artificial tasks. In the current study 3,mg/kg caffeine was found to improve steering accuracy in a 1,h simulated drive. Measures of mood and performance on a sustained attention task also showed the benefits of caffeine. These findings suggest that laboratory results reflect a general benefit of caffeine that may also be observed in real-life situations. Other evidence examining the effects of caffeine on performance efficiency over the working day has shown the benefits of caffeine consumption on measures of sustained attention and alertness. This study also provided evidence suggesting that caffeine is often consumed when alertness is low to maximise alertness and performance efficiency. The implications of these findings for road safety are also considered. Copyright © 2001 John Wiley & Sons, Ltd. [source] Daytime sleepiness during Ramadan intermittent fasting: polysomnographic and quantitative waking EEG studyJOURNAL OF SLEEP RESEARCH, Issue 2 2003Rachida Roky Summary During the lunar month of Ramadan, Muslims abstain from eating, drinking and smoking from sunrise to sunset. We reported previously that Ramadan provokes a shortening in nocturnal total sleep time by 40 min, an increase in sleep latency, and a decrease in slow-wave sleep (SWS) and rapid eye movement (REM) sleep duration during Ramadan. During the same study, the effects of Ramadan intermittent fasting on daytime sleepiness were also investigated in eight healthy young male subjects using a quantitative waking electroencephalograph (EEG) analysis following the multiple sleep latency test (MSLT) procedure. This procedure was combined with subjective alertness and mood ratings and was conducted during four successive experimental sessions: (1) baseline (BL) 15 days before Ramadan, (2) beginning of Ramadan (R11) on the 11th day of Ramadan, (3) end of Ramadan (R25) on the 25th day of Ramadan, (4) recovery 2 weeks after Ramadan (AR). During each session, four 20-min nap opportunities (MSLTs) were given at 10:00, 12:00, 14:00 and 16:00 h and were preceded by rectal temperature readings. Nocturnal sleep was recorded before each daytime session. Subjective daytime alertness did not change in R25 but decreased in R11 at 12:00 h, and subjective mood decreased at 16:00 h, both in R11 and R25. During the MSLT, mean sleep latency decreased by an average of 2 min in R11 (especially at 10:00 and 16:00 h) and 6 min in R25 (especially at 10:00 and 12:00 h) compared with BL. There was an increase in the daily mean of waking EEG absolute power in the theta (5.5,8.5 Hz) frequency band. Significant correlations were found between sleep latency during the MSLT and the waking EEG absolute power of the fast alpha (10.5,12.5 Hz), sigma (11.5,15.5 Hz) and beta (12.5,30 Hz) frequency bands. Sleep latency was also related to rectal temperature. In conclusion, Ramadan diurnal fasting induced an increase in subjective and objective daytime sleepiness associated with changes in diurnal rectal temperature. [source] Diurnal variations in the waking EEG: comparisons with sleep latencies and subjective alertnessJOURNAL OF SLEEP RESEARCH, Issue 3 2000Lafrance Daytime measures of sleep latency and subjective alertness do not correlate with one another, suggesting that they assess different aspects of alertness. In addition, their typical diurnal variations show very different time courses. Quantitative analysis of the waking electroencephalogram (EEG) has been proposed as an objective measure of alertness, but it is not clear how it compares with other measures. In this study, the waking EEG was measured in the daytime to determine the presence of diurnal variations in the activity of standard frequency bands and to compare these variations with the temporal patterns typical of sleep propensity and subjective alertness. Alertness was evaluated in four men and 12 women, aged 19,33 y. Assessments were conducted every 2 h, from 10.00 to 24.00, in the following order: a visual analogue scale of alertness, a waking EEG recording and a sleep latency test. The waking EEG was recorded with eyes open. For each recording session, 32,60 s of artefact-free signals were selected from the C3/A2 derivation, then subjected to amplitude spectral analysis. Four EEG frequency bands showed significant diurnal variations: delta, theta, sigma and beta1. None of these variations showed a significant correlation with the temporal patterns of sleep latencies or subjective alertness. At the individual level, however, theta band activity increased when subjective alertness decreased, suggesting that the theta band can be used to monitor variations in alertness in a given individual, even at the moderate levels of sleepiness experienced during the daytime. [source] | ||||||||||