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We used a novel computerized decision-making task to compare the decision-making behavior of chronic amphetamine abusers, chronic opiate abusers, and patients with focal lesions of orbital prefrontal cortex (PFC) or dorsolateral/medial PFC. We also assessed the effects of reducing central 5-hydroxytryptamine (5-HT) activity using a tryptophan-depleting(More)
Groups of subjects whose primary drug of abuse was amphetamine or heroin were compared, together with age- and IQ-matched control subjects. The study consisted of a neuropsychological test battery which included both conventional tests and also computerised tests of recognition memory, spatial working memory, planning, sequence generation, visual(More)
RATIONALE There is converging evidence for impairments in decision-making in chronic substance users. In the light of findings that substance abuse is associated with disruptions of the functioning of the striato-thalamo-orbitofrontal circuits, it has been suggested that decision-making impairments are linked to frontal lobe dysfunction. We sought to(More)
Cognitive function was assessed in chronic drug users on neurocognitive measures of executive and memory function. Current amphetamine users were contrasted with current opiate users, and these two groups were compared with former users of these substances (abstinent for at least one year). Four groups of participants were recruited: amphetamine-dependent(More)
Reinforcing properties of psychoactive substances are considered to be critically involved in the development and maintenance of substance dependence. While accumulating evidence suggests that the sensitivity to reinforcement values may generally be altered in chronic substance users, relatively little is known about the influence reinforcing feedback(More)
OBJECTIVE Previously, we reported that opiate users enrolled in methadone treatment made 'risky' choices on a decision-making task following a loss of points compared with heroin users and healthy volunteers. One possible explanation for this behaviour is that methadone users were less sensitive to punishment on immediately preceding unsuccessful trials. (More)