Subliminal Reward Modulate Cognitive Control

In our daily life, we often use cognitive control to regulate behaviors when we are in the face of changing environment or complicated task demands or varied information. Cognitive control is the ability to configure ourselves for the performance of specific tasks through appropriate adjustments in perceptual selection, response biasing, and the online maintenance of contextual information. The Dual Mechanisms of Control (DMC) theory suggests that cognitive control consists of two modes:proactive control (anticipatory and sustained control during cue encoding and maintenance periods) and reactive control (control engaged just-in-time during task probe or response periods) and there is a tradeoff between these two kinds of control to optimize task performance. The DMC account provides a strong prediction about the temporal dynamics and location of brain activity under proactive versus reactive control. Proactive control should be associated with sustained and/or anticipatory activation of lateral PFC, by contrast, reactive control should be reflected intransient activation of lateral PFC, along with a wider network of additional brain regions.It is very important to investigate the mechanism of reward modulating human behaviors. Several researches had shown that reward could modulate cognition by increase attention, working memory, executive control. The reward context was associated with a shift towards proactive control. Recently, some researchers began to study on how does subliminal reward cue impact cognition, and they found that awareness of reward cue is not necessary for it works. Reward cue can improve working memory and cognitive control even when it occurs outside of conscious. Unfortunately, the study on subliminal reward were rarely and behavioral study mostly.Therefore, it is necessary to investigate the mechanism of subliminal reward modulating cognitive control. In this study, participants engaged in a reward version of AX-CPT task, which introduced some reward-related cue and feedback. These reward-related cue and feedback were presented supraliminally (284ms followed by a mask for16ms) or subliminally (16ms followed by a mask for284ms) before and after each cue-probe sequence of AX-CPT task. Participants were told to complete baseline condition, supraliminal reward condition and subliminal reward condition one by one. In baseline condition, the reward-related cue was presented subliminally and participants performed the AX-CPT task without any instruction that future blocks would be performed with financial incentives. During subsequent two condition participants would gain some money if they response correctly and fastly. The only different between supraliminal and subliminal reward condition was the presentation of reward-related cue and feedback, the former was supraliminal while the latter subliminal. We use fMRI to record the brain activity when participants performed.The behavioral results revealed that subliminal reward cue could improve cognitive control and led to the proactive control perference just like supraliminal reward cue did. Yet supraliminal reward cue also improve the performance in non cognitive control trails while subliminal reward cue have no affects.The fMRI result revealed that supraliminal reward condition increase the activity of frontal region,such as bilateral inferior frontal gyrus, bilateral insula, medial frontal gyrus and anterior cingulate cortex while subliminal reward condition increase the activity of left hippocampal. In addition, ROI showed significant proactive control activition in supraliminal reward condition while no significant in subliminal reward condition. These results indicated that supraliminal and subliminal reward may be different in neuro mechanism, and hippocampal may play an important role in subliminal reward condition.