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Abstract
Negative symptoms in schizophrenia have been linked to selective reinforcement learning deficits in the context of gains combined with intact loss-avoidance learning. Fundamental mechanisms of reinforcement learning and choice are prediction error signaling and the precise representation of reward value for future decisions. It is unclear which of these mechanisms contribute to the impairments in learning from positive outcomes observed in schizophrenia. A recent study suggested that patients with severe apathy symptoms show deficits in the representation of expected value. Considering the fundamental relevance for the understanding of these symptoms, we aimed to assess the stability of these findings across studies. Sixty-four patients with schizophrenia and 19 healthy control participants performed a probabilistic reward learning task. They had to associate stimuli with gain or loss-avoidance. In a transfer phase participants indicated valuation of the previously learned stimuli by choosing among them. Patients demonstrated an overall impairment in learning compared to healthy controls. No effects of apathy symptoms on task indices were observed. However, patients with schizophrenia learned better in the context of loss-avoidance than in the context of gain. Earlier findings were thus partially replicated. Further studies are needed to clarify the mechanistic link between negative symptoms and reinforcement learning.
Highlights
Value-based decision-making relies on a learning mechanism at the time of outcome, which relates to relevant previous situations (PE signaling in the midbrain) and a “storage unit” that holds a representation of the expected value of choice options
Selective reinforcement learning deficits with reduced learning from positive, but intact learning from negative outcomes has been reported in patients with schizophrenia[15,16,17], which is in line with a proposed neurocomputational model of dopamine induced basal ganglia-cortex interactions[15,18]
The present study aimed to investigate probabilistic reinforcement learning in the context of gain and loss-avoidance in a sample of schizophrenia patients and how learning and valuation relates to the severity of apathy
Summary
The selective learning deficit in the context of reward constitutes a plausible factor causing and/or maintaining negative symptoms, especially motivational deficits manifesting themselves as apathy It is unclear whether these findings reflect impairments in positive PE signaling during outcomes or in the precise representation of expected reward values to guide decision-making. Based on the paper of Gold and colleagues[20], we expected that in the transfer test phase high apathy patients, compared to low apathy patients and controls, would show a weaker preference for rewarded stimuli over the stimuli that avoided loss, which would be indicative of impaired expected value representation
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