Elsevier

Biological Psychiatry

Volume 62, Issue 7, 1 October 2007, Pages 756-764
Biological Psychiatry

Original Article
Selective Reinforcement Learning Deficits in Schizophrenia Support Predictions from Computational Models of Striatal-Cortical Dysfunction

https://doi.org/10.1016/j.biopsych.2006.09.042Get rights and content

Background

Rewards and punishments may make distinct contributions to learning via separate striatal-cortical pathways. We investigated whether fronto-striatal dysfunction in schizophrenia (SZ) is characterized by selective impairment in either reward- (Go) or punishment-driven (NoGo) learning.

Methods

We administered two versions of a probabilistic selection task to 40 schizophrenia patients and 31 control subjects, using difficult to verbalize stimuli (experiment 1) and nameable objects (experiment 2). In an acquisition phase, participants learned to choose between three different stimulus pairs (AB, CD, EF) presented in random order, based on probabilistic feedback (80%, 70%, 60%). We used analyses of variance (ANOVAs) to assess the effects of group and reinforcement probability on two measures of contingency learning. To characterize the preference of subjects for choosing the most rewarded stimulus and avoiding the most punished stimulus, we subsequently tested participants with novel pairs of stimuli involving either A or B, providing no feedback.

Results

Control subjects demonstrated superior performance during the first 40 acquisition trials in each of the 80% and 70% conditions versus the 60% condition; patients showed similarly impaired (<60%) performance in all three conditions. In novel test pairs, patients showed decreased preference for the most rewarded stimulus (A; t = 2.674; p = .01). Patients were unimpaired at avoiding the most negative stimulus (B; t = .737).

Conclusions

The results of these experiments provide additional evidence for the presence of deficits in reinforcement learning in SZ, suggesting that reward-driven learning may be more profoundly impaired than punishment-driven learning.

Section snippets

Relevance of Dopamine System Function Models to SZ

This framework has the potential to offer a differentiated account of feedback-driven learning deficits in SZ. Whereas PD involves mainly BG hypofunction brought on by dopamine depletion, SZ may be characterized by DA dysfunction in both PFC and the BG. While the severity and consequences of PFC hypofunction in schizophrenia appear to be profound (Weinberger 1987, Weinberger and Berman 1988), BG dysfunction in schizophrenia may be more mild, based on findings of relatively intact procedural

Patients

Forty outpatients with a diagnosis of schizophrenia, based on the Structured Clinical Interview for DSM-IV (SCID-I) (First et al. 1997), were recruited from the Maryland Psychiatric Research Center (MPRC) (Table 1). All patients were clinically stable, as determined by their treating clinician. All patients were tested while receiving stable medication regimens (no changes in type or dose within 4 weeks of study). Most patients (28/40) were on antipsychotic monotherapy, while 12 patients were

Acquisition of Contingencies

In our first experiment, patients demonstrated dramatic impairment in the acquisition of probabilistic contingencies, whereas healthy subjects demonstrated clear learning of the two most frequently rewarded stimuli. Two-way ANOVAs for data from both early acquisition and postacquisition tests revealed main effects of group (see Supplementary text and Supplementary Figure 1 for details), indicating that patients performed worse than control subjects in experiment 1, regardless of reinforcement

PSS Task Performance

We examined the performance of patients and control subjects on two probabilistic learning and transfer tasks. In the first version, using Hiragana characters, patients exhibited profound impairment in the acquisition of probabilistic contingencies. This seemed to reflect impairments in the use of feedback to modify behavior on a trial-by-trial basis, consistent with models of PFC/OFC dysfunction. In the second experiment (using clip art stimuli), patients showed impairment in the early

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      Many studies have examined reward processing of positive and negative outcomes in schizophrenia using various reinforcement or reward learning paradigms (Abohamza et al., 2020). In a series of studies, Gold, Waltz, and colleagues (Gold et al., 2012; Strauss et al., 2011; Waltz et al., 2007) found consistent evidence that motivation impairments in schizophrenia were associated with reduced learning ability to positive outcomes (such as poor performance on a Go-learning task), but intact learning from negative, or loss, outcomes (NoGo-learning). Thus, people with schizophrenia may engage in fewer motivated behaviors than healthy comparison participants because they are less sensitive or less able to learn how to obtain rewards but successful in knowing how to avoid losses or punishments (Strauss et al., 2014).

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