Effects of Caffeine on EEG Theta/Beta Ratio and Cognitive Control

Cognitive control driven by the prefrontal cortex (PFC) of the brain is thought to be important for goal-directed control over stimulus-driven processes. EEG-measured spontaneous theta/beta ratio (TBR) may potentially be used as an electrophysiological marker for this PFC-mediated cognitive control. In the present study the investigators further examine TBR as an electrophysiological marker for cognitive control, by administering caffeine to forty healthy female participants. After a first training session, participants will visit the lab twice in separate weeks, during which they will orally consume one capsule containing 200mg of caffeine, and one capsule containing a placebo substance (double-blind and random order of administration). EEG will be measured before and after capsule consumption, and cognitive control tasks will be administered after capsule consumption. Generally, the investigators expect that caffeine will decrease TBR and thereby increase cognitive control. Additionally, the investigators expect that individual differences in baseline frontal (reflected by TBR) and central dopaminergic (reflected by spontaneously-measured eye-blink rates; EBR) activity will moderate the relationship between caffeine and cognitive control. Furthermore, the effects of caffeine on specifically hypervigilance for threatening distractors (taking into account a possible moderating role of trait anxiety) were examined as a separate research question.