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Disrupting sleepiness and fatigue during the post-lunch dip by environmental factors may result in a decrease in human errors and accidents, and enhance job performance. Recent studies have shown that both red white light as well as blue white light can have a positive effect on human alertness and mental functioning. In the present study, the light intervention was evaluated for its effectiveness on alleviating the post-lunch dip. Twenty healthy volunteers experienced 117 min of four light conditions preceded by a 13-min initial dim light while performing a continuous performance test (CPT) and undergoing recording of the electroencephalogram (EEG): blue-enriched white light (12,000 K, 500 lx, BWL), red saturated white light (2,700 K, 500 lx, RWL), normal white light (4,000 K, 500 lx, NWL), and dim light (<5 lx, DL) conditions. Other outcome measures were subjective sleepiness, mood, and performance tests (working memory, divided attention, and inhibitory capacity). We found that exposure to both BWL and RWL conditions decreased the lower alpha-band power compared to the NWL and DL conditions. No significant differences were observed in subjective sleepiness and mental performance during sustained attention, working memory, and inhibitory capacity tasks between NWL, RWL, and BWL conditions. The present findings suggest that both RWL and BWL, compared to NWL condition, can improve the physiological correlates of alertness in EEG measurements. However, these changes did not translate to improvements in task performance and subjective alertness. [ABSTRACT FROM AUTHOR]

Twelve male students who normally ate a large lunch and 12 who normally ate only a light lunch performed a sustained attention task before and after eating a light lunch and before and after eating a heavy lunch. The speed and accuracy of performance were measured; so also were temperature, pulse rate and subjective estimates of tension, alertness and hunger. The changes brought about by the meals were examined. Speed alone showed no change over the lunch interval. Of the remaining seven measures, only temperature, which seems to reflect endogenous processes, was unaffected by the size of the lunch that was eaten. Accuracy, pulse rate and hunger were influenced by the size of the habitual lunch as well as by the size of the experimental lunch. Tension and alertness were responsive only to the size of the experimental lunch. The results are discussed in relation to diurnal rhythms, with a particular emphasis on the acquisition of endogenous component processes, as exemplified by habits of eating. [ABSTRACT FROM AUTHOR]