Active action selection in reward-modulated visual perception

Although studies have shown that reward modulates both visual processing and action selection, these components are often treated in isolation. It thus remains unclear how the visual processing links to the motor components. This study answers this question in a cue-target paradigm, where a cue indicates whether a response to the following target can lead to the receipt of a monetary reward or not. The target, a visual form with a left- or right-pointing head, required a corresponding left- or right-hand response, with the cue uninformative of the target direction. Electroencephalography (EEG) signals were recorded to show how the visual and motor activities were modulated by reward. Behavioral results showed facilitated reaction times in the reward condition than in the no-reward condition. EEG results showed that, during the cue-target interval, the activity amplitudes at the contralateral and the ipsilateral sides of the target direction were equally enhanced by reward over both the motor cortex and the visual cortex. After target onset, reward-enhanced motor cortex activity persisted for both sides, whereas this pattern was not observed over the visual cortex. Overall, selective processing of the target direction occurred earlier in the visual cortex than in the motor cortex, and this latency difference was shortened in the reward condition after visual sensory discrimination. Taken together, the derived results suggested that reward proactively enhanced the preparation of the target-relative motor candidates before the visual analysis and facilitated the integration of the analyzed visual information with motor components for action selection.