Impairment of response inhibition and flexibility, effects of alcohol and information processing

Abstract

This thesis developed go-stop and change tasks to measure the effects of a moderate dose of alcohol on tasks of executive cognitive processes when low or high information processing was required to respond to go-signals. Two experiments, consisting of sixteen male social drinkers each, tested the performance of one group under .62g/kg alcohol (n=8) or under a placebo (n=8). Alcohol Study 1 demonstrated that alcohol impaired inhibitory control on a go-stop task, and the degree of impairment did not differ when the cognitive processing required to respond to a go-signal was increased. Alcohol Study 2 used a change paradigm task that replicated the findings of Alcohol Study 1 and demonstrated that alcohol impaired response flexibility by slowing the time required to make a second response following a failure to inhibit a first response. The results of the studies showed that alcohol can impair response inhibition and flexibility without affecting the reaction time to go-signals. Contrary to theories that propose alcohol impairment increases when information processing demands are greater, greater impairment under alcohol was not observed when the processing demands of the tasks were increased. Previous studies have typically used indirect, proxy measures of inhibitory control and response flexibility. In contrast, the present research built upon methods developed in cognitive science that directly measure response inhibition and flexibility. This approach made it possible to assess the effects of a moderate dose of alcohol on inhibitory control and response flexibility when the processing demands of the task were manipulated. The research has developed a novel approach for investigations of drug-effects on cognitive control of behaviour, and provides new information on the impairing effect of alcohol on cognitive processes.