Reward Improves Cognitive Control By Enhancing Signal Monitoring

Reward plays a crucial role in enhancing response inhibition.While it is generally assumed that the process of response inhibition involves signal monitoring and the stopping of action.Stopping in response to a stop signal requires a subject to attend to a cue,appreciate its significance,and engage response inhibition.However,it is unclear whether this reflects a direct impact of reward on response inhibition or rather an indirect mediation via signal monitoring.In addition,some literature employed pretask reward cueing to study the effect of reward,but the role of pretask reward cueing on cognitive control was influenced by response strategies rather than stimulus processing.To address the above issues,the present study designed four novel variants of the classical stop signal task that combined the reward with certain stimuli or stimulus features and held stimulus-processing demands constant while varying attention demands.The first part of this study is consisted of three experiments.For experiment 1,participants tried to cancel responses on trials that were interrupted by the infrequent triangle but not to slow the initiation of the response.The results indicated that the SSRTs could be further accelerated if successful response inhibition were rewarded.Experiment 2 involved separation of signal monitoring from the stop signal task.Participants responded by pressing the left or right button when the trials were interrupted by the infrequent triangle.The results showed that participants could monitor a signal faster when the signal was associated with reward and conflicted with current behavior tendencies.Accordingly,we considered that the individual could more quickly activate behavior in correspondence with the signal and control the conflict because the signal monitoring was enhanced by reward,which indicated that the process needs more attention.Experiment 3 is the same as the second experiment,except that when trials were interrupted by an inverse triangle,participants made a dual button press.We found that the reaction time of the reward-related signal was shorter than that of the reward-unrelated signal in Go trials,even though the processing of the stop signal depletes the attention resource.These findings indicate that the reward-related signal captures more attention and enhances signal monitoring.The second part of this study used functional magnetic resonance imaging(fMRI)to investigate the neurocognitive mechanism of reward effect on response inhibition.Here,we employed a revised stop-signal task(SST)that separated these two cognitive elements,byincluding a continue signal that required the same motor response as in go trials,but also attention to a cue,as in stop trials.We first confirmed the engagement of the right inferior frontal gyrus(IFG)during stop and continue trials,both of which required the attentional capture of the task-relevant cue,but only one of which required motor inhibition.The pre-supplementary motor area(pre-SMA)was specifically activated by the contrast of the stop trials with the continue trials.The results indicated that the IFG played an important role in attentional capture by unexpected stimuli,while the pre-SMA was responsible for the direct control of motor inhibition.Behavioral performance of the SST was improved by reward,and moreover,reward induced an increase in IFG activity.In addition,this advantageous reward effect was associated with enhanced connectivity between the anterior cingulate cortex and the IFG.These results indicated that the reward facilitation effect on response inhibition was indirect,occurring via a change in attentional processing.The present data confirm the specific function of the IFG and pre-SMA in response inhibition and provide straightforward evidence that reward can increase attentional capture-related activation in the IFG,which in turn improves the performance of response inhibition.In summary,these findings show that the reward-related signal captures more attention than bias for the enhancement of signal monitoring,thereby leading to more efficient stimulus processing and improving cognitive control.