Cortical mechanisms of action selection: the affordance competition hypothesis

TLDR

Animals must choose among possible actions and specify their parameters, yet neurophysiological evidence challenges a serial decision‑making model. This study proposes that the brain specifies multiple potential actions in parallel rather than serially. The authors model a system where dorsal visual inputs generate competing action representations in fronto‑parietal cortex, biased by prefrontal and basal ganglia signals. Simulations of the model reproduce key neurophysiological patterns and behavioral phenomena, supporting the affordance competition hypothesis.

Abstract

At every moment, the natural world presents animals with two fundamental pragmatic problems: selection between actions that are currently possible and specification of the parameters or metrics of those actions. It is commonly suggested that the brain addresses these by first constructing representations of the world on which to build knowledge and make a decision, and then by computing and executing an action plan. However, neurophysiological data argue against this serial viewpoint. In contrast, it is proposed here that the brain processes sensory information to specify, in parallel, several potential actions that are currently available. These potential actions compete against each other for further processing, while information is collected to bias this competition until a single response is selected. The hypothesis suggests that the dorsal visual system specifies actions which compete against each other within the fronto-parietal cortex, while a variety of biasing influences are provided by prefrontal regions and the basal ganglia. A computational model is described, which illustrates how this competition may take place in the cerebral cortex. Simulations of the model capture qualitative features of neurophysiological data and reproduce various behavioural phenomena.