Dissociation between medial temporal lobe and basal ganglia memory systems in schizophrenia

Szabolcs Kéri, Orsolya Nagy, Oguz Kelemen, Catherine E. Myers, Mark A. Gluck

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45 Citations (Scopus)

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 et al. (2003) [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.

Original languageEnglish
Pages (from-to)321-328
Number of pages8
JournalSchizophrenia Research
Volume77
Issue number2-3
DOIs
Publication statusPublished - Sep 15 2005

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Keywords

  • Acquired equivalence
  • Antipsychotics
  • Basal ganglia
  • Learning
  • Medial temporal lobe
  • Memory
  • Parkinsonism
  • Schizophrenia

ASJC Scopus subject areas

  • Psychiatry and Mental health
  • Biological Psychiatry

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