Event-related potentials were recorded from 11 subjects
after ingesting caffeine (250 mg) or placebo. Subjects were
instructed to attend selectively to stimuli with a specified
color (red or blue) in order to react to the occurrence of a
target within the attended category. Reaction times revealed
faster responses for the caffeine condition, whereas no
differences in strategy were observed. Color attention effects
were identified as frontal selection positivity, occipital
selection negativity, and N2b, whereas target detection was
reflected in P3b. Effects of treatment were found as a more
positive-going frontal P2 component in the caffeine condition.
In addition, an interaction between attention and treatment
could be observed on the N2b component. This pattern of results
suggests that caffeine yields a higher overall arousal level,
more profound processing of both attended and unattended
information, and an acceleration of motor processes.