The Neural Mechanisms Underlying The Effects Of Reward On Externally And Intentionally Initiated Control Processes

Control processes refers to the top-down processes driven explicitly or intentionally via that people perform actions flexibly and strategically during goal-directed behavior.Previous action control model has distinguished between endogenously driven,intentional action and exogenously driven,habitual,or automatic action.As a traditional motivation incentives in daily life,reward always enhance human performance.Previous studies primarily aim to investigate the effects of reward on control processes driven by exogenous cues,there is little known about the effects of reward on control processes driven by human intention.Moreover,several studies have claimed that the effect of reward on specific-aspect of control processes(e.g.,cognitive flexibility)can be modulated by the sequential changes in reward value,not only by the directly comparisons between the high-and low-reward value.Even though this evidence extend our understanding of the relationship between the reward and flexibly control processes,the neural basis of this phenomenon is still unclear.Apart from that,prior work suggest that although reward prompt human performance in most cases,motivational level(always induced by reward)has no effects on human behavior in some specific case(e.g.,in unconsciously triggered decision-making task),therefore,it should be futher discussed whether reward elicit extensive influence on human control processes(especially the unconsciously triggered control processes)Building on the aforementioned work,we,therefore,developed four studies(totally 5 experiments)to detect how reward influence external and intentional control processes systematically using event-related potentials and time-frequency analysis.In the first study and second study,we investigated the influence of the “absolute value” of reward on the conscious and unconscious externally triggered(in the first study)as well as intentionally initiated(in the second study)inhibitory control by comparing human performance straightforwardly in highand low-value reward condition.In the third study and forth study,we further explored the influence of the “relative value” of reward on the externally triggered(in the third study)and intentionally initiated(in the forth study)control processes,while adding the factor of sequential changes in reward value into the independent variables and by using the task-cuing paradigm(in the third study)and the voluntary task-switching paradigm(in the forth study).In the first study,we combined the high-and low-value reward stimuli(presentation in block-wise fashion)and a modified Go/No-Go paradigm to detect whether the reward can influence conscious and unconscious externally initiated inhibitory control.The results showed that the high-value reward can promote both consciously and unconsciously triggered externally inhibitory control,as expressed by the enhanced frontal P3 amplitude and theta oscillation for high-value reward relative to low-value reward.These findings suggest that frontal P3 component/theta oscillation may be implicated in the modulation of reward on conscious and unconscious externally triggered inhibitory control.In the second study,we tried to delineate the neural mechanisms underlying the effect of reward on conscious/unconscious intentional inhibition via two experiments.In the Experiment 1,we used a modified of Go/No-Go/Choose task to detect the neural basis of conscious/unconscious intentional inhibition.The results showed that conscious intentional inhibition resulted in an enhanced reversed N2 and a later P3 amplitudes as well as heightened low beta oscillatory activity in consciously presented No-Go trials relative to consciously presented Go trials,reflecting the early-stage processing of decision making and late-stage processing of motor execution.Besides,we observed that the intentional inhibitory processing can operate without consciousness,as evidenced by enhanced P3 amplitude and theta oscillation in unconsciously presented No-Go trials relative to unconsciously presented Go trials.In the Experiment 2,we combined the high-and low-value reward stimuli(presentation in block-wise fashion)and the modified Go/No-Go/Choose paradigm to detect whether the reward can influence conscious and unconscious intentional inhibition.The results suggested that high-value reward enhanced unconscious intentional inhibition,as exhibited by larger inversed N2 and P3 as well as stronger early-stage and late-stage low beta oscillations in consciously presented No-Go trials relative to consciously presented Go trials.Unfortunately,although we also observed the intentional inhibition can operate without consciousness,the reward had no effects on the unconsciously initiated intentional inhibition,this result imply the boundary effect of reward-induced unconscious control processes.In the third study,we manipulated the sequential change in reward value,and combined reward stimuli and a task-cuing switching paradigm to investigate how the sequential changes in reward influence human cognitive flexibility.The behavioral results showed that the increased in reward value(increased condition)elicited smaller switch cost than remain-high in reward value(remain-high condition),suggesting that increased in reward could enhance human cognitive flexibility.In the phase of cue-target,we observed a larger frontal contingent negative variation(CNV)and a stronger frontal theta oscillation for increased condition than for remain-high condition,and observed an evident parietal alpha oscillation for both increased condition and remain-high condition.In the phase of post-target,we observed a larger frontal N2 and a stronger frontal theta oscillation for increased condition than for remain-high condition.These findings demonstrate that the frontal theta oscillation may be implicated in the top-down regulation of sequential change in reward value on human externally triggered flexibly control processes,whereas the parietal alpha oscillation may be involved in the extraction and updating in working memeory and task-sets in the duration of task-preparation.In the forth study,we also manipulated the sequential change in reward value,and combined the reward and a voluntary task switching paradigm to investigate how the sequential changes in reward influence human voluntary cognitive flexibility.The behavioral results showed that the increased in reward value(increased condition)elicited smaller voluntary switch cost and larger “voluntary switching rate” than remain-high in reward value(remainhigh condition),suggesting that increased in reward could enhance human cognitive flexibility.In the phase of cue-target,we observed a smaller frontal theta oscillation and a stronger parietal low beta oscillation for increased condition than for remain-high condition.In the phase of posttarget,we observed a larger frontal N2 and a smaller frontal theta oscillation for increased condition than for remain-high condition.These findings demonstrated that individual deployed more cognitive resources strategically on the phase of task-preparation occurring in the parietal cortex to improve performance via reducing the interference of information of previous taskset on current task in human perfrontal cortex.In sum,these findings suggest that the neural signatures of reward-modulated externally driven and intentionally initiated control processes were distinct,the prefrontal theta oscillation was implicated in the modulation of reward on externally driven control processes,whereas the prefrontal/parietal low beta oscillation was involved in the modulation of reward on intentinally initated control processes.Furthermore,we proposed that reward can mediate the control processes persistently via the feature of “absolute value”,and can modulate the control processes flexibility and strategically via the feature of “relative value”,implying that reward can extensively influence human control processes.However,we also observed the null-effect of reward on the processing of unconscious decision-making,suggesting the boundary effect of reward-modulated control processes.