DOPAMINE DYNAMICS IN HUMAN ANTERIOR CINGULATE CORTEX ARE SHAPED BY PAVLOVIAN BIASES DURING MOTIVATIONAL BEHAVIOUR

A large body of research indicates that dopamine (DA) within the striatum and other subcortical regions support action and valence processing, including signalling reward prediction errors (RPEs). However, its role in cortical regions, and in particular in the human brain, is less clear. We obtained electrochemical estimates of sub-second DA fluctuations from clinical depth electrodes implanted into the anterior cingulate cortex (ACC) – a region involved in behavioural control and conflict processing – in epilepsy patients. The patients performed a motivational Go/NoGo task in which they had to learn to press a button (Go) or refrain from pressing a button (NoGo) following a visual cue in order to obtain a reward (Win) or avoid a punishment (Avoid). Computational modelling revealed that, while patients learned the cue-response mappings in an instrumental manner, they were also subject to Pavlovian biases to Go in anticipation of reward and NoGo in anticipation of punishment. Neurally, DA reflected this Pavlovian modulation: DA levels increased after the visual cue when the upcoming action was congruent with Pavlovian biases (Go-to-Win and NoGo-to-Avoid); while DA levels preceding a Go scaled positively with instrumentally learned cue-action values, this response was stronger in anticipation of reward; and DA levels following feedback scaled positively with RPEs in Pavlovian-congruent states (Go-to-Win and NoGo-to-Avoid) but negatively in Pavlovian-incongruent states (Go-to-Avoid and NoGo-to-Win). These results indicate that DA at the level of the ACC is part of a control process that adjusts behavioural policies towards actions that are more beneficial than those dictated by Pavlovian biases.