Caffeine Maintains Arousal Level and Prevents Change of Electroencephalogram Spectral Powers with Time at Rest

Abstract

Caffeine is one of the most commonly used central stimulants. It is frequently used for its mood and performance enhancing effects. The daily caffeine intake of Korean university students and North American adults are approximately 120 mg and 200 mg, respectively. 1,2 Caffeine increases vigilance and diminishes sleepiness, and administration of these doses stimulates attention and restores performance degraded by factors such as fatigue and boredom. 3 Central stimulating effects of caffeine have been evaluated by quantitative electroencephalography (qEEG) analysis. Although many studies have used qEEG analysis, inconsistencies still remain regarding the effects of caffeine on electroen-cephalography (EEG) spectral powers. 4 These inconsistencies could be attributed to experimental differences between studies. Many studies have been conducted to clarify the effects of various parameters, such as, dose-dependency, 5-7 eyes open or closed, 6,8,9 and vigilance control. 9 However, recording duration for qEEG analysis has not been well considered. According to multiple sleep latency test (MSLT) studies, sleep latency in normal adults during the day is around 15 min. 10 Considering that the duration of the EEG recordings are generally 10-30 min, sleep can occur during recording and thus EEG rhythms can change. Accordingly, the selection of a part from a recording for qEEG analysis can affect the outcome of studies on the effects of caffeine on EEG spectral powers. In contrast to subjective questionnaires or neuropsychological tests, qEEG analysis has the advantage of being able to provide objective descriptions of temporal changes. Therefore, we examined the effect of caffeine effect on temporal change by qEEG by dividing the recording period into two segments and by comparing the qEEG parameters of Objectives: Although many studies have used quantitative electroencephalography (qEEG) analysis, some inconsistencies remain regarding the effects of caffeine. Among variables producing inconsistencies, the effect of selecting analyzing segment on caffeine study was examined by comparing the first and second halves of a recording session. Methods: Eleven subjects underwent two EEG recording sessions for decaf-feinated (control group) and caffeinated coffee (caffeine group) with at least a 48 hr interval. The log absolute powers (BA) and log relative powers ratio (BRr) of 8 frequency bands were compared between groups and between the first 5-min (c1) and second 5-min (c2) recording segments. Results: As BA's were compared between groups, Delta2 and Theta1 were lower at both segments in the caffeine group and these differences were greater at c2. Increased differences were mainly due to temporal change in the control group. As BRr's were compared, Delta2 was lower at both segments and the difference was greater at c2 in the caffeine group. Theta1 was lower at c2, Beta BRr was higher at c1, while Alpha2 BRr was higher at c2 in the caffeine group. The dissimilarity indices between groups increased about twofold with. The dissimilarity indices between segments were about three-times larger in the control group than in the caffeine group. Conclusions: The results indicate that selection of analyzing segment is one important factor for quantitative EEG, and suggest that caffeine prevent decline of arousal, and that the simple 'dissimilarity index' can well represent the effect of caffeine on EEG spectral powers. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licens-es/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.