Competing neural representations of choice shape evidence accumulation in humans.

Making adaptive choices in dynamic environments requires flexible decision policies. Previously, we showed how the evidence accumulation process that drives decisions shifts when outcome contingencies change (1). Using in silico experiments, here we show how the cortico-basal ganglia-thalamic (CBGT) circuits can feasibly implement shifts in the evidence accumulation process. When action contingencies change, dopaminergic plasticity redirects the balance of power, both within and between action representations, to divert the flow of evidence from one option to another. This model predicts that when competition between action representations is highest, the rate of evidence accumulation is lowest. This prediction was validated in in vivo experiments on human subjects, using fMRI, which showed that 1) evoked hemodynamic responses can reliably predict trialwise choices and 2) competition between action representations, measured using a classifier model, tracked with changes in the rate of evidence accumulation. These results paint a holistic picture of how CBGT circuits manage and adapt the evidence accumulation process in mammals.