Effects of chlorpromazine on lateralization,cued reaction time,and dichotic listening

In a double-blind cross-over design sixteen subjects took 50 mg of chlorpromazine or placebo in tablet form 2 hours prior to completing a dichotic listening and simple reaction time task with and without warnings. In the simple reaction time task, blocks of 80 stimuli were presented to each ear with and without warning cue under drug and placebo conditions. On the dichotic listening task the expected right ear advantage for reporting digits was obtained. While the drug had no main effect on the number of errors, there were more trials on which an ear advantage was present than in the placebo condition. In the reaction time task there were main effects of drug, warning cue and foreperiod: warnings facilitated reaction; chlorpromazine retarded reaction; and reaction times were most facilitated by warning foreperiods in excess of 1200ms. Several findings were of interest: On uncued trials, with placebo, right ear responses were faster than those for stimuli presented to the left ear. Drug also interacted with foreperiod duration. These results were interpreted in the light of Tucker and Williamson’s (1984) review of the role of Pribram and McGuinness’s Arousal and Activation sytems in lateralized behavior.