Differential effects of alcohol, cocaine, and opioid abuse on event-related potentials recorded during a response competition task.

The present study examined the abilities of cocaine-dependent and opioid-dependent patients and healthy, non-dependent volunteers to execute a task requiring rapid shifts in cognitive set. Sixty-six residential treatment program patients, characterized by a history of either cocaine (n=37) or opioid (n=29) dependence, and 18 non-drug-dependent community volunteers were evaluated. The task involved the execution of right- or left-hand button press responses that were either spatially-compatible or incompatible with a directional cue. Performance and event-related electroencephalographic (EEG) activity were recorded throughout the task. Analyses revealed that button press responses were significantly slower and less accurate for all of the groups when spatial conflict was introduced. The amplitude of a slow EEG potential (SP), emerging approximately 500 ms after stimulus onset, showed the normal effect of spatial conflict for the opioid-dependent and non-dependent groups, but not for subjects in the cocaine-dependent group. Correlational analyses restricted to data from the cocaine-dependent group showed that this abnormal SP amplitude was not related to the quantity, frequency, or recency of their cocaine use; it only correlated with their comorbid alcohol use. The results of the major analyses, in combination with the results of a neuroanatomical localization algorithm applied to the SP data, suggest that comorbid alcohol use disrupts normal task-related activation of the anterior cingulate, cerebellum, and prefrontal cortex. The present results have implications for the assessment of specific cognitive problems which could foster drug abuse.