title: Working memory contributions to reinforcement learning impairments in schizophrenia.
abstract: Previous research has shown that patients with schizophrenia are impaired in reinforcement learning tasks. However, behavioral learning curves in such tasks originate from the interaction of multiple neural processes, including the basal ganglia- and dopamine-dependent reinforcement learning (RL) system, but also prefrontal cortex-dependent cognitive strategies involving working memory (WM). Thus, it is unclear which specific system induces impairments in schizophrenia. We recently developed a task and computational model allowing us to separately assess the roles of RL (slow, cumulative learning) mechanisms versus WM (fast but capacity-limited) mechanisms in healthy adult human subjects. Here, we used this task to assess patients' specific sources of impairments in learning. In 15 separate blocks, subjects learned to pick one of three actions for stimuli. The number of stimuli to learn in each block varied from two to six, allowing us to separate influences of capacity-limited WM from the incremental RL system. As expected, both patients (n = 49) and healthy controls (n = 36) showed effects of set size and delay between stimulus repetitions, confirming the presence of working memory effects. Patients performed significantly worse than controls overall, but computational model fits and behavioral analyses indicate that these deficits could be entirely accounted for by changes in WM parameters (capacity and reliability), whereas RL processes were spared. These results suggest that the working memory system contributes strongly to learning impairments in schizophrenia.
authors.affiliation: Department of Cognitive, Linguistics, and Psychological Sciences, Brown University, Providence, Rhode Island 02912, and anne_collins@brown.edu.
authors.forename: Anne G E
authors.initials: AG
authors.lastname: Collins
authors.affiliation: Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, Maryland 21201.
authors.forename: Jaime K
authors.initials: JK
authors.lastname: Brown
authors.affiliation: Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, Maryland 21201.
authors.forename: James M
authors.initials: JM
authors.lastname: Gold
authors.affiliation: Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, Maryland 21201.
authors.forename: James A
authors.initials: JA
authors.lastname: Waltz
authors.affiliation: Department of Cognitive, Linguistics, and Psychological Sciences, Brown University, Providence, Rhode Island 02912, and.
authors.forename: Michael J
authors.identifier: http://orcid.org/0000-0001-8451-0523
authors.initials: MJ
authors.lastname: Frank
mesh_terms: D000328:Adult; D014150:Antipsychotic Agents / Q000008:administration & dosage / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D059032:Learning Curve; D007859:Learning Disabilities / Q000209:etiology / Q000523:psychology*; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008960:Models, Psychological; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012054:Reinforcement, Psychology; D012559:Schizophrenia / Q000150:complications / Q000188:drug therapy; D012565:Schizophrenic Psychology
chemical_list: D014150:Antipsychotic Agents
keywords: computational model; reinforcement learning; schizophrenia; working memory