Phase-tuned modulation during reward expectancy in human anterior insular cortex.

Reward expectancy engages the anterior insular cortex (AIC) to coordinate cognitive allocation. Using intracranial electroencephalographic data from epilepsy patients navigating a virtual T-maze, we identified reward-specific brain patterns (RBPs) that were preactivated in the AIC prior to reward onset. This pre-activation was followed by phase-amplitude coupling (PAC) between theta oscillations and gamma activity, with coupling strength positively correlated with the pre-activation level across contacts. Furthermore, this PAC exhibited a phase-precession-like effect (PPLE), characterized by a progressive shift of peak gamma activity to earlier theta phases across successive navigation rounds. Participants exhibiting stronger PPLE in the AIC showed greater trial-by-trial improvements in reward-collection performance. Taken together, these findings reveal a precise phase-tuned timing mechanism in the AIC that supports reward-directed behavior. Specifically, oscillatory coordination initiated by representational pre-activation, is dynamically refined through PPLE across successive exposures to the same reward. This mechanism accelerates responses to impending rewards, thereby optimizing adaptive behavior.