Lateralization of Brain Function in Task Switching:Evidence Based on tDCS and TMS Technology
Task switching is one component of executive function.It refers to the process of switching from one cognitive task to another,emphasizing the ability to flexibly switch between tasks,goals or psychological settings.Because task switching is the most basic daily cognitive activity of human beings,it is of great importance to study its neural mechanisms.In the research on the neural mechanism of task switching,researchers have made some research achievements in the two research fields by using transcranial direct current stimulation(tDCS)to explore the lateralization effects of the two hemispheres of the brain.Firstly,researchers concluded that the frontal lobe is the core brain area of task switching,in which the left hemisphere plays an important role.The main method is to change the tDCS montage.For example,to separate the contribution of left and right DLPFC,researchers put anode in the left DLPFC and cathode in the right OFC for a group,and in the other group,cathode was put in the left DLPFC and anode was put in the right OFC.All participants received tDCS for 15 minutes at 1 mA intensity and the results showed that the left DLPFC receiving anode stimulation could improve the ability of task switching.However,not all experiments obtained similar results.For example,some studies used the elderly as the participants and took the cue paradigm as the switching task.All participants received tDCS for 30 minutes at 1 mA intensity each day with 10 consecutive days.However,it was found that the individual switching cost did not decrease and the performance of task switching did not improve.Therefore,it could not be proved that the left hemisphere of DLPFC is the dominant hemisphere of task switching.It was speculated that the reason for the controversy in these studies may be that tDCS is only an auxiliary tool for cognitive training rather than an independent cognitive regulation tool.As a result,in some studies,the advantages of left DLPFC in task switching cannot be highlighted.In addition,even if the anode tDCS on left DLPFC may improve the performance of task switching independently of training.However,some variables weaken the effect of tDCS,such as aging factors.Secondly,the left and right hemispheres of the frontal region cooperate to form neural loop movement to support task switching.By changing the tDCS montage,researchers found that the endogenous preparation in the process of task switching needs the main force of the right DLPFC to participate in and inhibit the inappropriate task setting.Meanwhile,the exogenous regulation relies on the left DLPFC to perform a top-down adaptation process.In addition,different task types will affect the neural circuit movement in the right and left hemispheres.Future studies should be improved in five aspects.First of all,it is of significant to improve the application level of tDCS technology.For example,researchers should pay attention to the effectiveness of tDCS stimulation,experimental ethics and individual differences.Moreover,in addition to the frontal lobe,it is necessary to study other brain regions,such as the parietal lobe.Moreover,other neural regulation technologies such as Transcranial Magnetic Simulation(TMS for short)and biofcedback could be used in future studies,and future studies with functional magnetic resonance(fMRI)combined with online tDCS should be performed to test the asymmetric involvement of right and left hemispheres in task switching.Besides,researchers should explore the mystery of brain function lateralization in task switching from the perspectives of physiological anatomy,molecular genetics,psychiatry,and other disciplines.Last but not least,future studies should take deductive reasoning and inductive reasoning as the guiding ideology.
task switchinglateralization of brain functiontDCSTMS
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