Objective: Previous research has shown that caffeine produces a general increase in arousal. The present study examined caffeine-induced
arousal effects on performance and auditory ERPs. We sought components showing amplitude changes without topography changes, as
would be expected of a pure arousal amplification of source activity.
Methods: The effects of a single oral dose of caffeine (250 mg) were examined in a randomised double-blind placebo-controlled repeatedmeasures
cross-over study. Subjects abstained from caffeine for 4 h before the testing sessions, which were conducted, in the afternoon,
one week apart. A simple auditory Go/NoGo task was used, with a random mix of 75 tones at 1000 Hz and 75 at 1500 Hz. All tones were
60 dB SPL, 50 ms duration (rise/fall time 5 ms), with SOA 1100 ms.
Results: There was a reduction in RT, but no effects on omission or commission errors. The major ERP effects of caffeine were focal
rather than global increases in P1, P2 and P3b amplitudes to Go stimuli, with no changes in latency. There were no effects on N1 or
N2 to Go stimuli, and no effects on any components in response to NoGo stimuli.
Conclusions: The results suggest that caffeine differentially improves aspects of the processing related to response production and task
performance, contrary to the widespread amplification of ERP component amplitudes, and latency reductions, expected of an increase
in general arousal.
Significance: These results add auditory ERP data to the list of complex effects of caffeine on brain function and behaviour. They appear
to rule out a simple arousal interpretation, and suggest directions for future research.