While a Monkey Waits: Electrocortical Events Recorded During the Foreperiod of a Reaction Time Study

Emanuel Donchin, University of South Florida
D. Otto
L. K. Gerbrandt
K. H. Pribram


Electrical potentials in frontal, motor and parietal cortex of young rhesus monkeys during three foreperiod reaction time tasks were studied using transcortical Pt-PtCl electrodes, long time-constant amplifiers and computer-averaging techniques. A prominent positive-negative-positive wave form was observed maximally in postcentral cortex when monkeys held a key down during a fixed interval between two stimuli. When response was withheld until the second stimulus, sustained negativity occurred frontally but not postcentrally. The relationship of contingent negative variation, motor potentials and the observed electrocortical patterns is discussed.