| 1 Background and ObjectiveExecutive function refers to the conscious control of thinking and behavior in psychological process,including decision-making,attention,working memory,cognitive flexibility and other cognitive processes.Executive dysfunction widely exists in a variety of neuropsychiatric diseases,and is closely related to the decline of daily living ability and function.This study intends to explore the effect of low-frequency repetitive transcranial magnetic stimulation(rTMS)and cTBS stimulation on executive function and its neural mechanism by using Event related potential(ERP),so as to provide basis for further study on the relationship between cerebral cortex and executive function.2 MethodExperiment 1 Task switching paradigm was used to study the cognitive flexibility in executive function.Thirty one healthy subjects were randomly assigned to receive rTMS stimulation(1hz rTMS or sham rTMS)to the left dorsolateral prefrontal cortex(DLPFC)twice.Then the task switching procedure was immediately performed and the behavioral and ERP results were recorded.The sequence of real and sham stimuli was balanced,and the interval between the two stimuli was about one week.Experiment 2For the cTBS experiment,24 healthy subjects underwent a single blind crossover design.They received repetitive stimulation to the left DLPFC twice(cTBS stimulation and sham cTBS stimulation).Then the task switching procedure was immediately performed and the behavioral and ERP results were recorded.The sequence of real and sham stimuli was balanced,and the interval between the two stimuli was about one week.3 ResultExperiment 1 ERP analysis showed that there is a significant switching effect in frontal and central scalp locations,and the amplitude of P2 in switch trials was greater than that in non-switch trials.In the frontal scalp locations,the N2 amplitude in switch trials is more negative than that in non-switch trials in sham stimulation,but there was no significant difference in rTMS stimulation.In central and parietal channels,there was significant rTMS stimulation effect on P3 and LPC component.The amplitude of rTMS stimulation was smaller than that of sham stimulation.Experiment 2 For the cTBS experiment,ERP analysis showed that the stimulation effect of cTBS in P2(140-240ms)of central channels was statistically significant,the P2 amplitude of cTBS stimulation was smaller than that P2 evoked by sham cTBS(P<0.01);the stimulation effect of cTBS in N2(260-340ms)in frontal channels was significant,and the N2 amplitude of cTBS stimulation was more negative than that of N2 evoked by sham cTBS(P<0.01).There was also a significant difference in switching effect.the N2 amplitude of switch condition was more negative than that of nonswitch condition(P<0.05).In frontal,central and parietal channels,there was significant stimulation effect of cTBS on P3,and the P3 amplitude of cTBS stimulation was smaller than that of P3 induced by sham cTBS(P<0.05).There was also significant switching effect in the frontal channels.The P3 amplitude of nonswitch condition was larger than that of switch condition(P<0.01).In parietal channels,there was a significant cTBS stimulation effect of LPC component.The amplitude of cTBS stimulation was smaller than that of sham cTBS(P<0.05).4 ConclusionLow frequency rTMS of the left DLPFC can cause decline of executive function,resulting in the change of N2 effect and the decrease of P3,LPC component in the parietal region during task switching,which may damage the information processing and updating process in task switching.cTBS of the left DLPFC can cause decline of executive function,resulting in the decrease of P2 amplitude in central channels and parietal channels,the decrease of N2 amplitude in frontal channels and parietal channels,the decrease of P3,LPC in frontal,central and parietal channels.rTMS stimulation of the left DLPFC showed changes in the EEG components during task switching,especially cTBS stimulation,which is of positive significance for the evaluation and treatment of executive function. |
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