Academic journal article Cognitive, Affective and Behavioral Neuroscience

Reduced Susceptibility to Confirmation Bias in Schizophrenia

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Reduced Susceptibility to Confirmation Bias in Schizophrenia

Article excerpt

Published online: 31 January 2014

© Psychonomic Society, Inc. 2014

Abstract Patients with schizophrenia (SZ) show cognitive impairments on a wide range of tasks, with clear deficiencies in tasks reliant on prefrontal cortex function and less consistently observed impairments in tasks recruiting the striatum. This study leverages tasks hypothesized to differentially recruit these neural structures to assess relative deficiencies of each. Forty-eight patients and 38 controls completed two reinforcement learning tasks hypothesized to interrogate prefrontal and striatal functions and their interaction. In each task, participants learned reward discriminations by trial and error and were tested on novel stimulus combinations to assess learned values. In the task putatively assessing fronto-striatal interaction, participants were (inaccurately) instructed that one of the stimuli was valuable. Consistent with prior reports and a model of confirmation bias, this manipulation resulted in overvaluation of the instructed stimulus after its true value had been experienced. Patients showed less susceptibility to this confirmation bias effect than did controls. In the choice bias task hypothesized to more purely assess striatal function, biases in endogenously and exogenously chosen actions were assessed. No group differences were observed. In the subset of participants who showed learning in both tasks, larger group differences were observed in the confirmation bias task than in the choice bias task. In the confirmation bias task, patients also showed impairment in the task conditions with no prior instruction. This deficit was most readily observed on the most deterministic discriminations. Taken together, these results suggest impairments in fronto-striatal interaction in SZ, rather than in striatal function per se.

Keywords Schizophrenia · Reward · Decision-making


The psychological impairments observed in schizophrenia (SZ) involve most, but not all, cognitive functions (Gold, Hahn, Strauss, & Waltz, 2009). Deficits in tasks thought to rely on the integrity of the frontal lobes, such as working memory and executive control (Barch & Ceaser, 2012; Lesh, Niendam, Minzenberg & Carter 2011), have been repeatedly observed and modeled (Cohen & Servan-Schreiber, 1992). Episodic memory deficits, likely related to both prefrontal and medial temporal lobe abnormalities, are also prominent (Ragland et al., 2009). In contrast, deficits in reinforcement learning and reward-based decision making, dependent on both the basal ganglia and prefrontal cortex, have been observed in some cases, but not in others (Averbeck, Evans, Chouhan, Bristow & Shergill 2011;Goldetal.,2009; Somlai, Moustafa, Kéri, Myers & Gluck 2011; Waltz, Frank, Robinson, & Gold, 2007; Weickert et al., 2002).

When studying patient impairments in cognitive function, it is important to distinguish between global performance deficits and selective alterations in particular processes putatively related to underlying neural mechanisms. Notably, several reinforcement learning studies have reported that patients with SZ exhibit selective deficits in learning from probabilistic rewards/gains, and not punishments/losses (Gold et al., 2012; Strauss et al., 2011; Waltz et al., 2007; Waltz, Frank, Wiecki, &Gold,2011; Waltz et al., 2010). While initial reports attributed this pattern to deficiencies in striatal dopaminergic function similar to those observed in Parkinson's disease (Waltz et al., 2007; Waltz et al., 2011), subsequent studies have implied that the source of dysfunction may lie in reward-processing areas of the prefrontal cortex and fronto-striatal communication (Gold et al., 2012; Strauss et al., 2011; Waltz et al., 2010). Here, we employed tasks designed to assess the function and interaction of the prefrontal cortex and striatum in an attempt to assess their relative perturbation in SZ. These tasks were chosen to assess biases in learning and decision-making processes that arise in healthy individuals-biases that are thought to reflect the signatures of striatal function or prefrontal-striatal communication. …

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