| In the laboratory environment,conflict effect reflects the ability of conflict processing“within-trials”,which is referred to longer reaction times?RT?in incongruent trials?e.g.33433?compared with congruent trials?e.g.33333?.Conflict effect indicates the current ability of cognitive control in conflict conditions.As the foundation of cognitive control,the cognitive conflict occurred in early stage.The conflict monitoring theory suggests that the medial frontal cortex?MFC?and anterior cingulate cortex?ACC?monitor the conflict information and transmit signals to other brain regions.Meanwhile,the MFC modulates the conflict-relevant brain regions,and improves the levels of cognitive control to resolving the conflict.Previous studies have proved that the event-related potential?ERP?component Flanker N2,to some extent,indicates the conflict monitoring and the cognitive-related ability of conflict processing within-trials.N2 reflects the dynamic regulation information of cognitive modulated by ACC,and addresses the degree of conflict response.The conflict effect could be affected by feature repetition within continuous trials and contingency learning.However,the relationships between N2 as the index of conflict degree and white matter integrality are still nuclear.In addition,recently,several studies have investigated the test-retest reliability of conflict processing,using both behavioral and electrophysiological indices.Despite the robust trait-like characteristics of conflict processing,it is interesting that reaction times under all conditions are significantly shorter in the second session than in the first session,even when the sessions are two weeks apart.Differences in reaction times across two sessions may suggest practice-based improvement,reflecting the saying“practice makes perfect”.Thus,we tried to investigate?1?whether N2amplitudes were more negative in incongruent conditions compared with congruent conditions,excluding the effects of feature integration,contingency learning and previous incongruent trials,and?2?whether N2 amplitude related to white matter integrality in“pure”condition,and?3?whether conflict effect,as index of conflict processing abilities within trials,could be improved across two separate sessions to examining practice-based improvement effect,and?4?whether individual difference of conflict processing improvement related to white matter tracts within the conflict network.Thirty-seven participants completed the Flanker task.Simultaneously,the EEG data were recorded,and the DTI data were collected before the day of behavioral testing.All the participants were asked to complete the Flanker task again after two weeks.First,we analyzed the conflict effect of RT and N2 in“pure”condition,and the relationships between RT?CI-CC?and N2?CI-CC?amplitude.Then,we examined the relationships between the N2?CI-CC?amplitude and DTI parameters.Finally,we divided all participates into two groups depending on the direction of change in conflict effect,and assessed the between-group differences in the whole brain white matter.The current results showed significant conflict effect within RT?CI-CC?and N2?CI-CC?amplitude.The larger N2?CI-CC?amplitude was,the longer RT?CI-CC?was.The fractional anisotropy?FA?in the right superior longitudinal fasciculus?SLF?significantly positively correlated with N2amplitude cost.And individual variability in conflict effect improvement related with the axial diffusivity in the right SLF.Our findings indicate that the higher white matter integrity of right SLF,which may serve as the main fiber bundle connecting the frontal lobe to parietal lobe,means the higher intensity of information exchange between the two cortices contribute to the better behavior of individuals. |
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