Abstract
A large body of research attributes learning deficits in schizophrenia (SZ) to the systems involved in value representation (prefrontal cortex, PFC) and reinforcement learning (basal ganglia, BG) as well as to the compromised connectivity of these regions. In this study, we employed learning tasks hypothesized to probe the function and interaction of the PFC and BG in patients with SZ-spectrum disorders in comparison to healthy control (HC) subjects. In the Instructed Probabilistic Selection task (IPST), participants received false instruction about one of the stimuli used in the course of probabilistic learning which creates confirmation bias, whereby the instructed stimulus is overvalued in comparison to its real experienced value. The IPST was administered to 102 patients with SZ and 120 HC subjects. We have shown that SZ patients and HC subjects were equally influenced by false instruction in reinforcement learning (RL) probabilistic task (IPST) (p-value = 0.441); however, HC subjects had significantly higher learning rates associated with the process of overcoming cognitive bias in comparison to SZ patients (p-value = 0.018). The behavioral results of our study could be hypothesized to provide further evidence for impairments in the SZ-BG circuitry; however, this should be verified by neurofunctional imaging studies.
Highlights
Humans learn how to behave both through rules and instructions as well as through environmental daily experiences
The authors of this study showed reduced confirmation bias among patients in comparison to healthy control (HC) participants, which has been attributed by the authors to reduced prefrontal-striatal communication that led to a paradoxical improvement in patients’ performance on the task
We found no significant associations between the performance on the Instructed Probabilistic Selection Task (IPST) task and clinical measures or general functioning of the patients; behavioral results obtained in our study depend on the sampling methods, such as the percentage of patients with first-episode psychosis or schizoaffective disorder, the predominant symptomatology, or currently prescribed treatment
Summary
Humans learn how to behave both through rules and instructions as well as through environmental daily experiences. There are various dual-process models describing separable decision-making systems that contribute to rule-based/instructed choices versus those based on experience/procedural learning [1]. Systems dependent on the PFC encode task instructions and rapidly update representations based on single outcomes for flexible control of choices [5], while systems based on the BG integrate reinforcement contingencies slowly by trial and error to support maximally adaptive responses to current stimuli [6,7]. SZ has been associated with reduced functional connectivity across fronto-temporal networks supporting verbal encoding [9], hippocampal-prefrontal and prefrontal-thalamic networks during working-memory tasks [10,11], occipito-temporal networks supporting semantic processing [12], and dysfunctional integration between brain regions involved in reinforcement learning [13,14]. In recent years, studies have looked into impairments in several systems with the focus on dysfunctional interactions between them in order to gain deeper understanding of the neural basis of cognitive impairments in SZ [16]
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