Effects of Dietary Caffeine on Topographic EEG after Controlling for Withdrawal and Withdrawal Reversal

Abstract

Background/Aims: Despite several decades of research into the effects of caffeine on EEG, few consistent findings have emerged. Notwithstanding the likelihood that differences in methodology may explain some of the inconsistency, confidence in the published findings is undermined by the failure in previous studies to control for the effects of caffeine withdrawal and withdrawal reversal. Methods: Participants (n = 22) alternated weekly between ingesting placebo and caffeine (1.75 mg/kg) 3 times daily for 4 consecutive weeks. EEG activity was measured at 32 sites during eyes closed, eyes open, and performance of a vigilance task. Results: Caffeine was found to have few and modest effects on EEG in the theta and alpha bandwidths, and no effects in the delta and beta bandwidths. Evidence was found of withdrawal, withdrawal reversal, and tolerance in relation to observed increases in theta power during task performance; withdrawal and withdrawal reversal in relation to increases in alpha power during all three behavioural conditions (eyes closed, eyes open, and task performance), and withdrawal-induced adverse effects in relation to aspects of subjective mood. Conclusion: The finding of similar increases in theta power following caffeine challenge and acute caffeine withdrawal casts doubt on whether caffeine may be viewed as having direct stimulant effects. Results could suggest that change in drug state, whether in the form of acute caffeine withdrawal or challenge, may be disruptive to electrophysiological activity in the brain.

Effects of dietary caffeine on EEG, performance and mood when rested and sleep restricted

“…Consistent with these speculations, Keane et al (2007) found that caffeine generally had few and modest effects on EEG power in a study that controlled for withdrawal reversal in ways similar to recent studies of the effects of caffeine on performance, mood and blood pressure (James and Gregg, 2004a,b;. Furthermore, while increases in theta activity were found following caffeine withdrawal (possibly indicating withdrawalinduced sleepiness), similar increases were also observed after acute caffeine challenge following long-term abstinence.…”

“…James, 1998;. Whereas we have previously examined acute and chronic effects of caffeine ingestion and caffeine withdrawal (James, 1998;Keane et al, 2007), the present study focused on chronic effects while introducing the additional variable of sleep restriction. In brief, with participants serving as their own controls over the successive weeks of the experiment, effects were examined while participants were normally rested and when sleep restricted, with and without caffeine.…”

“…Performance was measured using two versions of the sustained attention to response task (SART; Robertson et al, 1997), consisting of the numbers 1-9 presented individually in random order (Random SART) and in a fixed order from 1 to 9 repeated (Fixed SART; see Keane et al, 2007 for a full description). SART has the characteristics of simplicity, monotony and repetitiveness typical of tasks that previous research has shown are sensitive to the effects of caffeine (e.g.…”

Electrophysiological Studies in Healthy Subjects Involving Caffeine

“…It is possible that a direct effect on muscle fiber or lower motor neuron is relevant [5,9]. On the other hand, the central effect is large and well documented [19,[27][28][29][30][31][32][33][34]. CSP as estimated using low intensities is a sensitive method to detect the influence of caffeine on the central nervous system [18].…”

“…However, the EEG changes are not striking and are possibly influenced by acute caffeine withdrawal or ingestion [33,34].…”