Dopamine, Affordance and Active Inference

TLDR

Dopamine’s role in behaviour and decision‑making is typically framed by reinforcement learning and optimal decision theory. The study proposes a Bayes‑optimal view of dopamine and uses simulations of cued sequential movements to demonstrate how tonic dopamine changes can produce diverse behavioural outcomes. Dopamine modulates cue precision, balancing sensory input and prior beliefs within a hierarchical generative model that predicts movements, allowing context changes to alter agent behaviour. The simulations provide a Bayes‑optimal model of contextual uncertainty and set switching, and show that altering prediction‑error precision can mimic Parkinsonian‑like pathological behaviours.

Abstract

The role of dopamine in behaviour and decision-making is often cast in terms of reinforcement learning and optimal decision theory. Here, we present an alternative view that frames the physiology of dopamine in terms of Bayes-optimal behaviour. In this account, dopamine controls the precision or salience of (external or internal) cues that engender action. In other words, dopamine balances bottom-up sensory information and top-down prior beliefs when making hierarchical inferences (predictions) about cues that have affordance. In this paper, we focus on the consequences of changing tonic levels of dopamine firing using simulations of cued sequential movements. Crucially, the predictions driving movements are based upon a hierarchical generative model that infers the context in which movements are made. This means that we can confuse agents by changing the context (order) in which cues are presented. These simulations provide a (Bayes-optimal) model of contextual uncertainty and set switching that can be quantified in terms of behavioural and electrophysiological responses. Furthermore, one can simulate dopaminergic lesions (by changing the precision of prediction errors) to produce pathological behaviours that are reminiscent of those seen in neurological disorders such as Parkinson's disease. We use these simulations to demonstrate how a single functional role for dopamine at the synaptic level can manifest in different ways at the behavioural level.