CAFFEINE EFFECTS ON PERCEPTUAL AND MOTOR PROCESSES

The effects of a single dose of caffeine on specific information proce ssing operations were examined by using a visual selective attention t ask in which subjects were asked to select between a left and right ha nd response on the basis of two different target letters. The target w as presented on a predefined position in the visual field and was eith er presented alone or with flanker letters, calling for the correct, t he incorrect or no specific response. A dose of 3 mg/kg body weight ca ffeine or lactose, dissolved in a cup of decaffeinated coffee, was adm inistered double blind and deceptively to overnight abstinence coffee drinkers. Behavioural measures were supplemented by psychophysiologica l measures. The present results replicated the basic findings obtained in this paradigm. The results indicated that the time to localise the target decreased and response preparation started earlier after caffe ine than after placebo. These caffeine effects did not interact with t he time subjects spent on the task or with the reaction time distribut ion, which might be due to a high level of practice. (C) 1997 Elsevier Science Ireland Ltd.