Profiles of cognitive dysfunction in chronic amphetamine and heroin abusers

Groups of subjects whose primary drug of abuse was amphetamine or heroin we re compared, together with age- and IQ-matched control subjects. The study consisted of a neuropsychological test battery which included both conventi onal tests and also computerised tests of recognition memory, spatial worki ng memory, planning, sequence generation, visual discrimination learning, a nd attentional set-shifting. Many of these tests have previously been shown to be sensitive to cortical damage (including selective lesions of the tem poral or frontal lobes) and to cognitive deficits in dementia, basal gangli a disease, and neuropsychiatric disorder. Qualitative differences, as well as some commonalities, were found in the profile of cognitive impairment be tween the two groups. The chronic amphetamine abusers were significantly im paired in performance on the extra-dimensional shift task (a core component of the Wisconsin Card Sort Test) whereas in contrast, the heroin abusers w ere impaired in learning the normally easier intra-dimensional shift compon ent. Both groups were impaired in some of tests of spatial working memory. However, the amphetamine group, unlike the heroin group, were riot deficien t in an index of strategic performance Oil this test. The heroin group fail ed to show significant improvement between two blocks of a sequence generat ion task after training and additionally exhibited more perseverative behav ior oil this task. The two groups were profoundly, but equivalently impaire d on a test of pattern recognition memory sensitive to temporal lobe dysfun ction. These results indicate that chronic drug use may lead to distinct pa ttens of cognitive impairment that may be associated with dysfunction of di fferent components of cortico-striatal circuitry. (C) 2000 American College of Neuropsychopharmacology. Published by Elsevier Science Inc. All rights reserved.