| Objective: Although human behavior is regularly executed in a relativelyautomatic fashion, individuals often have to assert control over their attention,thoughts and behaviors in order to flexibly adapt to current goals—a processknown as cognitive control. Cognitive control is an essential aspect ofexecutive function and closely related to social and emotional functioning,self-regulation and mental health. Thus, it is not surprising that deficits incognitive control characterize many disorders, including cerebrovasculardisease，Parkinson’s disease，schizophrenia and depression. To find a way toimprove the cognitive control is becoming an important aspect of CognitiveNeuroscience.An increasing number of studies found that repetitivetranscranial magnetic stimulation (rTMS) as a non-invasive tool is effectivefor the improvement of cognition.But the related mechanisms are verycomplex,which is related with the history of synaptic activity in the stimulatedregion and the rTMS protocols. Based on the above background, our studyfocus on the effects of10Hz rTMS on left DLPFC in healthy youth, andcombine it with ERPs to explore the underlying mechanisms of rTMS and theduration of the effects.Methods: Specialized neurologists registered routine demographicdetails,including age,gender, education levels etc. Hamilton Anxiety Scale（HAMA），Hamilton Depression Scale（HAMD）, Mini-Mental StateExamination(MMSE), Montreal Cognitive Assessment (MoCA) were usedrespectively for the emotional and cognitive evaluation.Make sure that thereare no significant differences between the two groups in the demographicdetails, emotional and cognitive levels. Exclude the individuals withemotional and/or cognitive problems. Thirty-two healthy youth were randomly divided into two groups, receiving10Hz rTMS and sham rTMS respectivelyfor7consecutive days. The stimulation time was balanced among subjects andfixed in every participants. A computerised Stroop task was performed beforestimulation, immediately after stimulation and7days after stimulation.Meanwhile, the EEG was recorded. We would analyse the behavioural andelectrophysiological data in the three time points to explore the influence ofhigh-frequency rTMS on cognitive control.We used Independent-samples T-Test to compare the behavioural andelectrophysiological data of the same time point, repeated measures analysisof variance (ANOVA) for those of different time points and Post-hoc Newman–Keuls for multiple comparison.Results: First, both behavioral (RT and accuracy)(P＞0.05)and ERP (N2)data(P＞0.05)were not significant different between rTMS group and shamrTMS group at baseline. Second, both behavioral (RT and accuracy) and ERP(N2) data confirmed expected Incongruency effects in all time points(P＞0.01)(e.g., longer RT, lower accuracy and larger N2for incongruent vs. congruenttrials) and Gratton effects in the first time point(P＞0.05)(e.g., longer RT,lower accuracy for congruent trials following incongruent trials(C-I trials)then incongruent trials following incongruent trials (I-I trials)), indicating thattasks elicited the intended effects. Third, there are no significant differencebetween the two groups in behavioral data, as manifested by robust shorteningof RT and absence of Gratton effect in both groups at the second time point,without time×group interaction effect(P＞0.05). Fourth, most importantly,following7consecutive days stimulation, the mean amplitude of N2wassignificantly larger in both groups, more remarkable in the sham rTMSgroup(P＞0.05). In contrast, when came to the7days after stimulation, therewere no significant differences between the two groups(P＞0.05), indicatingthat the effect of rTMS can not last for7days. Finally, control analysesindicated that pre-to-post reductions in both RT and N2were not the result ofpractice effects, as manifested by no differences in RT(P＞0.05)，accuracy(P＞0.05)and N2(P＞0.05)between the first and third block before stimulation. Conclusion: The healthy youth can recuit more cognitive control toachieve better performance of Stroop task. High-frequency repetitivetranscranial magnetic stimulation can enhance the efficiency of Left DLPFCto improve cognitive control of healthy youth,because of the relative declineof the N2amplitude and absence of Gratton effect in rTMS group immediatelyafter stimulation. |
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