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Abstract:
Humans and animals use multiple control systems for decision-making, with the differential involvement of model-free (MF) and model-based (MB) systems casting light on psychiatric disorders. This involvement is subject to metacognitive regulation - as a form of control over control, meta-control. Here, we perturbed norepinephrine (NE) and dopamine (DA) neuropharmacologically with Propanalol and L-Dopa and examined control and metacontrol. We examined the effects of the drugs on choice and confidence ratings in two tasks: a conventional perceptual decision-making task used to study to confidence judgements, and a two-outcome task that offers an exquisitely fine decomposition of model-free and model-based choice and credit assignment. Using hierarchical Bayesian fitting, we found that Propranolol significantly decreased meta-cognitive ability while there was no effect of Levodopa-B. In the two-outcome task, Propranolol increased model-based behavior but had no effect on model-free behavior, while Levodopa-B had no effect on either. Regarding control over control, when control systems disagree, meta-control might naturally be exerted to determine which one should be favored. For instance, when decision-makers lack confidence, the model-based controller should be preferred because it is statistically superior. However, if decision-making is uncertain, the model-based system may not be reliable. In support of this hypothesis, we found that model-based behavior was less likely to increase after low confidence. Overall, we suggest that our study sheds new light on the role of noradrenergic and dopaminergic systems in different levels of control and points to potential avenues for mitigating dysfunction within and between these systems.
