Timing of caffeine's impact on autonomic and central nervous system measures: clarification of arousal effects.
The timing of caffeine effects on arousal levels was examined. From previous work in our laboratory, an increase in skin conductance level (SCL) was used as the marker of arousal increase, and we sought to identify the timing of this and related effects following caffeine ingestion. A single oral dose of caffeine (250 mg) was used in a randomised double-blind placebo-controlled repeated-measures cross-over study. Eyes-closed resting electroencephalogram (EEG) and autonomic data (SCL, heart rate, respiration rate, and systolic and diastolic blood pressure) during 2 min epochs that commenced every 4 min after ingestion, were analysed. The SCL placebo data were used to identify potential arousal measures prior to examining caffeine effects. Caffeine was associated with increased SCL, increased respiratory rate and a global reduction in alpha power. There were no significant cardiovascular effects of caffeine-induced arousal. These caffeine results are consistent with our recent electrodermal and EEG studies of arousal, and confirm the potential use of caffeine as a simple means of experimentally modifying arousal levels without task-related confounds.
Barry
Robert J
RJ
Brain & Behaviour Research Institute and School of Psychology, University of Wollongong, Wollongong, NSW 2522, Australia. robert_barry@uow.edu.au
Clarke
Adam R
AR
Johnstone
Stuart J
SJ
Rushby
Jacqueline A
JA
D000293:Adolescent; D000328:Adult; D000513:Alpha Rhythm / Q000187:drug effects; D001143:Arousal / Q000187:drug effects*; D001341:Autonomic Nervous System / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D002110:Caffeine / Q000097:blood / Q000494:pharmacology*; D002490:Central Nervous System / Q000187:drug effects*; D000697:Central Nervous System Stimulants / Q000097:blood / Q000494:pharmacology*; D003700:Delta Rhythm / Q000187:drug effects; D004311:Double-Blind Method; D004569:Electroencephalography / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D013826:Theta Rhythm / Q000187:drug effects
D000697:Central Nervous System Stimulants; D002110:Caffeine