Reduced model-based decision-making in schizophrenia

Abstract

Individuals with schizophrenia have a diminished ability to use reward history to adaptively guide behavior. However, tasks traditionally used to assess such deficits often rely on multiple cognitive and neural processes, leaving etiology unresolved. In the current study, we adopted recent computational formalisms of reinforcement learning to distinguish between model-based and model-free decision-making in hopes of specifying mechanisms associated with reinforcement-learning dysfunction in schizophrenia. Under this framework, decision-making is model-free to the extent that it relies solely on prior reward history, and model-based if it relies on prospective information such as motivational state, future consequences, and the likelihood of obtaining various outcomes. Model-based and model-free decision-making was assessed in 33 schizophrenia patients and 30 controls using a 2-stage 2-alternative forced choice task previously demonstrated to discern individual differences in reliance on the 2 forms of reinforcement-learning. We show that, compared with controls, schizophrenia patients demonstrate decreased reliance on model-based decision-making. Further, parameter estimates of model-based behavior correlate positively with IQ and working memory measures, suggesting that model-based deficits seen in schizophrenia may be partially explained by higher-order cognitive deficits. These findings demonstrate specific reinforcement-learning and decision-making deficits and thereby provide valuable insights for understanding disordered behavior in schizophrenia. (PsycINFO Database Record

Figure 1

A. Sample trial diagram: binary choice at stage one (spaceships) leads probabilistically to one of two second stage states (aliens) each with two choices that probabilistically result in reward/no-reward (treasure). B. Task structure: Each stage one choice has a common or rare transition to each of the second stage states.

Figure 2

First-stage choice behavior (coded as stay/shift) averaged across individuals within each group. Note: Error Bars are presented as standard errors.

Figure 3

Second-stage reaction time by transition type for each group Note: Error Bars are presented as standard errors.