title: Dissociation between medial temporal lobe and basal ganglia memory systems in schizophrenia.
abstract: The purpose of this study was to investigate basal ganglia (BG) and medial temporal lobe (MTL) dependent learning in patients with schizophrenia. Acquired equivalence is a phenomenon in which prior training to treat two stimuli as equivalent (if two stimuli are associated with the same response) increases generalization between them. The learning of stimulus-response pairs is related to the BG, whereas the MTL system participates in stimulus generalization. Forty-three patients with DSM-IV schizophrenia and 28 matched healthy controls participated. Volunteers received the Rutgers acquired equivalence task (face-fish task) by [Myers, C.E., Shohamy, D., Gluck, M.A. et al., 2003. Dissociating hippocampal versus basal ganglia contributions to learning and transfer. J. Cogn. Neurosci. 15, 185-193.], the California Verbal Learning Test (CVLT), and the n-back working memory test. The Rutgers acquired equivalence task investigates BG-dependent processes (stimulus-response learning) and MTL-dependent processes (stimulus generalization) with a single test. Results revealed that patients with schizophrenia showed a selective deficit on stimulus generalization, whereas stimulus-response learning was spared. The stimulus generalization deficit correlated with the CVLT performance (total scores from trials 1-5 and long-delay recall), but not with the n-back test performance. The number of errors during stimulus-response learning correlated with the daily chlorpromazine-equivalent dose of antipsychotics. In conclusion, this is the first study to show that patients with schizophrenia exhibit deficits during MTL-dependent learning, but not during BG-dependent learning within a single task. High-dose first generation antipsychotics may disrupt BG-dependent learning by blocking dopaminergic neurotransmission in the nigro-stiratal system.
authors.affiliation: Department of Psychiatry, University of Szeged, Semmelweis u. 6, Szeged, H-6725, Hungary. szkeri@phys.szote.u-szeged.hu
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Kéri
authors.forename: Orsolya
authors.initials: O
authors.lastname: Nagy
authors.forename: Oguz
authors.initials: O
authors.lastname: Kelemen
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Myers
authors.forename: Mark A
authors.initials: MA
authors.lastname: Gluck
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D014150:Antipsychotic Agents / Q000009:adverse effects; D001245:Association Learning / Q000187:drug effects; D001479:Basal Ganglia / Q000473:pathology*; D016022:Case-Control Studies; D018492:Dopamine Antagonists / Q000009:adverse effects; D005260:Female; D005793:Generalization, Psychological; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000139:chemically induced / Q000473:pathology*; D012559:Schizophrenia / Q000188:drug therapy / Q000473:pathology*; D013702:Temporal Lobe / Q000473:pathology*; D014163:Transfer, Psychology
chemical_list: D014150:Antipsychotic Agents; D018492:Dopamine Antagonists