Competition between action plans tracks with evidence accumulation during flexible decision-making

The ability to change your mind when the local environment changes relies critically on cortico-basal ganglia-thalamic (CBGT) circuits. In silico experiments on the CBGT pathways show how shifts in decision policy are driven by learning-induced changes in competition between action plans, both within and across action representations. We empirically validate this idea, using whole-brain hemodynamic imaging in homo sapiens to show how competition between action representations in CBGT circuits adaptively shifts the rate of evidence accumulation in response to action-outcome contingency changes. Significance Statement The world changes. Therefore, successful adaptation requires flexible decision making, and the knowledge that the world shifts should be taken into consideration when we weigh the evidence for staying with what we know against that for exploring new options. Using simulations and high-powered human neuroimaging, we show that a change in the best choice induces competition between action plans, slowing evidence accumulation to promote adaptive exploration. ### Competing Interest Statement The authors have declared no competing interest.