Tasks that are often used to measure inhibitory control are the go/no-go task and the stop signal reaction time task (SSRT). In the go/no-go task, cocaine-addicted individuals showed more errors of omission and commission than controls and this has been attributed to hypoactivation in dACC during stop trials109. In another study, this inhibitory behavioural deficit in cocaine users was exacerbated by a higher working-memory load; again, dACC hypoactivation was associated with deficient task performance110. Similarly, heroin-addicted men showed slower reaction times in the go/no-go task, along with hypoactivation in ACC and medial PFC111. Results from the SSRT are more difficult to interpret. For example, the ACC was hypoactive during successful response inhibitions compared to failed response inhibitions in cocaine-addicted men, and their behavioural performance was similar to that of controls112. The ACC was also hypoactive during both careful behavioural adjustment and risk taking on this task in abstinent alcoholics, particularly in subjects with higher alcohol urge at the time of the fMRI scan113. By contrast, the ACC was hyperactive during inhibition errors113, possibly because the abstinent alcoholics exercised a greater
