| Adaptive adjustment in response to changes in the environment is an essential feature of cognition control,and separable adjustment of proactive and reactive control may also rely on dissociable mechanisms,which has also become one of the important topics of interest for researchers.Within the corflict-control literature,research has focused on so-called proportion congruent(PC)effects as indices of adaptive regulation of cognitive control PC effects refer to the observation that interference effects are reduced in mostly incongruent conditions(high conflict)compare in mostly congruent conditions(low conflict),which can reflect the adaptive regulation of proactive and reactive control with appropriate experimental manipulations,respectively.Based on that,the present study investigate the differences in the neural dynamic corresponding to the adjustment of proactive and reactive control in Study Ⅰ,and the possible different modulatory effects of reward-an important moderator of cognitive control-on proactive and reactive control and their corresponding neural underpinning were further examined in Study Ⅱ,with the aid of EEG research techniques with high temporal resolution.In Study Ⅰ and Study Ⅱ,the proportion of incongruent trials in the task was varied by List Wide(LW)and Item Specific(IS)manner on the color-word Stroop task to elicit adaptive adjustment of proactive and reactive control,respectively.The LW task design is characterized by changing the global conflict frequency,as evidence by a significant reduction in interference effect in mostly incongruent block when most of the trials in a task block are incongruent,as compared with a mostly congruent block,reflecting adaptive adjustment of proactive control The IS task design was characterized by changing conflict frequency at the item level,as shown by the observation that the interference effect in mostly incongruent stimuli is smaller than that of mostly congruent stimuli whthin one task block,reflecting adaptive adjustment of reactive control.Thirty-one college students(mean age 21,SD=1.93,25 female)particpated in the LW task and IS task of Study Ⅰ.Consistent with previous studies in terms of behavioral results,PC effects steadily emerged for both the LW task and the IS task in terms of mean response time and accurcy.The results of neurophysiological indicators in the LW task that modulated the level of proactive control showed that the high-conflict block had 1)less differences in P2 amplitude between conflict and non-conflict trials related to visual early selective attention,and 2)lower theta rhythms power in frontal midline region(FMθ)reflecting stimulus-evoked control demands,compared to the low-conflict block.The result suggests that the enhanced proactive control in the high-conflict block facilitated early selection of task-relevant information and also led to a reduction in interference from conflict information,as evidenced by a reduction in stimulus-induced control demands.In contrast,the main neural manifestation in the IS task was that the MPN component related to conflict processing and the FMθ related to the control demands in the high-conflict stimulus differed less between conflict and non-conflict trials relative to the low-conflict stimulus,Suggesting that high-conflict stimuli in the IS task brought about elevated reactive control reduced the interference effects of the stimuli,reflected by the MPN component and FMθ.Study Ⅱ investigated the role of reward in the adaptive regulation of proactive control and reactive control as well as its neural dynamic.A total of 46 college students(mean age 23.04 years,SD=2.61,29 females)completed the LW task and IS task of Study Ⅱ,which added a manipulation of the reward condition to Study Ⅰ.Results showed that in the LW task that modulated proactive control:1)reward increased the accurcy of all conditions and 2)in the low-conflict block,reward reduced the difference in acurrcy between conflict and non-conflict trials,and increased the difference in lock-time on response FMθ power between the two.And in the IS task that modulated reactive control:1)reward improved accurcy in all conditions,and 2)reward also improved FMθ power that lock-time on stimulus and response.These results show that reward facilitates both proactive and reactive control and thus improves performance.However,in proactive control,reward facilitated the control process of motor execution preparation and reduced behavioral interference effects in the low proactive control condition In contrast,the facilitative effect of reward in reactive control was independent of the moderating effect of stimulus conflict level on reactive control and promoted behavioral performance and control engagement in all conditions.In conclusion,the current study provides adaptive and motivational regulation of proactive and reactive control of neural dynamic that deepen our knowledge of underlying mechanisms of cognitive control regulation.Specifically,conflict-induced proactive control acts in the perceptual selection phase and is characterized by a reduced control demand.In contrast,conflict-induced reactive control acts at the response execution stage and is characterized by an enhanced control demand.In addition,reward motivation enhances general attention processes and can facilitate the effective allocation of cognitive control to optimize behavioral performance at different levels of conflict. |
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