Separable influences of reward value on visual processing and choice

Abstract

Primate vision is characterized by constant, sequential processing and selection of visual targets to fixate. Although expected reward and reward value are known to influence both processing and selection of visual targets, the relationship between these effects remains unclear. Using a novel paradigm, we simultaneously measured the effects of expected reward on target selection and sensitivity to visual motion in monkeys. Monkeys freely chose between two visual targets and received a juice reward with varying probability for eye movements made to either of them. Targets were stationary apertures of drifting gratings, causing the endpoints of eye movements to these targets to be systematically biased in the direction of motion. We used this motion-induced bias as a measure of sensitivity to visual motion on each trial and utilized multiple measures to examine global and local effects of reward outcomes on choice and sensitivity to motion. Specifically, we used different reinforcement learning models to fit choice behavior and estimate reward values based on the integration of reward outcomes over multiple trials. Moreover, to compare the effects of reward value on choice and sensitivity to motion directly, we considered correlations between each of these variables and integrated reward outcomes on a wide range of timescales. We found that in addition to choice, sensitivity to visual motion was also influenced by reward value. However, choice was determined by the difference in reward values of the two options whereas sensitivity to motion was influenced by the sum of values. Moreover, models that best predicted visual processing and choice used sets of reward values based on different types of reward integration and timescales. Together, our results demonstrate separable influences of reward value on visual processing and choice, and point to the presence of multiple brain circuits for integration of reward outcomes.