| Cognitive control encompasses a variety of processes involved in generating and maintaining task-relevant goals and suppressing task-irrelevant goals,and conflict control is a critical part of it.The prefrontal cortex and other regions underpin it.The prefrontal cortex areas show protracted maturation during the adolescent period,and the performance on tasks requiring cognitive control during this stage of life can still be deficient compared with adult performance.Yet developmental studies of the conflict control process(including conflict resolve and conflict adaption)are scarce.By means of ICA decomposition in the revised Simon task,our EEG analyses identified two independent fmθ generators simultaneously active in or near the prefrontal(MPFC&MFC).And we separated theta power immediately before/after motor responses,identifying the neural development of conflict resolution and conflict adaptation.Furthermore,on this basis,links to reward and punishment provide insight into the motivation-control interactions that occur during adolescence.Study participants included 28 adolescents(M=12.47±0.33 years,11 females)and 24 adults(M=21.32±2.02 years,14females).In the adapted Simon task,participants had first to detect and localize the target(defined by a unique color or shape)before they could extract the information(the target’s vertical vs horizontal stripe orientation)that specified the required motor action:response to the target(one of the 6 location)using either their left-or their right-hand index finger,depending on the stripe orientation.Thus participants may react to lateralized target with a button press using either ipsilateral(congruent condition)or the contralateral(incongruent condition)index finger.As in previous studies,the conflict effect was the difference between congruence and incongruence.Conflict adaptation effects were also studied by analyzing the effect of the previous trial’s congruence in current interference.All participants completed the above task in three situations:baseline,reward,and punishment.Consistent with previous studies,behavioral results showed that adults had greater accuracy and faster response times than adolescents in all situations.And adolescents showed greater behavioral conflict effects and adaptation effects than adults.We dissociated pre-and post-response MPFC and MFC theta power as indices of the development of conflict control.And we found:On the MFC,both adolescents and adults showed higher pre-theta power than post-response;however,on the MPFC,adults showed a higher relative post-response theta power,whereas adolescents,similar to the MFC,had a higher pre-theta power than post-response.This finding may mirror developmental differences in conflict resolution and conflict adaptation due to the degree of differentiation of the prefrontal cortex as age.In the pre-response theta power of adolescents and adults,we found:(1)In the baseline situation,conflict effects were observed only on the MFC in both adults and adolescents,with no similar manifestations in MPFC.It suggests that both age groups may use MFC to solve the current conflict;(2)Reward and punishment regulate conflict control differently for the two age groups in the prefrontal.In the reward situation,conflict effects are still observed in adolescents’ MFC and MPFC for adults.The adult conflict effect of theta activity was positively correlated with the conflict effect at response time.In the punishment situation,in contrast to the absence of conflict effects in adolescents’ prefrontal activity,conflict effects were observed in both prefrontal clusters in adults.Motivation promotes the use of MPFC by adults to achieve conflict resolution,while the role of MFC is critical in conflict resolution in punishment situation.In the post-response theta power of adolescents and adults,we found:(1)In the baseline situation,conflict adaptation effects were observed in MFC in adolescents but not in adults;(2)Reward and punishment regulate conflict control mainly in adults’ prefrontal activities.Adaptation effects were observed in the MPFC of adults in the reward situation and in the MFC of adults in the punishment situation.Besides,the finding of both adaptation effects and a correlation with response time in MPFC and MFC suggests that two regions may be involved in conflict resolution and conflict adaptation in the motivation situation.(3)Relative to the baseline context,no adaptation effects were observed in the post-response theta activity of adolescents in the reward and punishment situation.This finding may be explained by the relatively large influence of motivation on adolescents’ current conflict resolving,but it does not promote adaptive post-conflict regulation.Based on the above,we concluded that(1)individual’s development contributes to the functional specialization of the two prefrontal regions;and(2)adults can cooperate flexibly with the two regions to complete conflict control in different motivational situations compared to adolescents. |
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