Caffeine and selective visual processing.

This work addressed five issues: a) Does caffeine modulate electroencephalogram (EEG) background activity in a manner consistent with the idea of cortical "arousal"? b) Is performance in a simple speeded task improved under caffeine? c) Is visual processing more selective under caffeine? d) Does caffeine affect sensory discrimination? and e) Does it affect motor processes? We presented 16 subjects with a visual selection task under conditions of either caffeine or placebo. Background EEG data, gathered before administration of the task, revealed that caffeine resulted in lower slow-alpha power, relative to placebo, which is consistent with the idea of increased cortical "arousal." During the selection task, subjects had to respond manually to a given target conjunction of spatial frequency and orientation.