The Neural Oscillation Mechanism Of Inhibiting Distractors In Working Memory

Working memory is a system for short-term storage and processing of information.It is the basis of various advanced cognitive functions,and is very important for people’s daily work and learning behavior.A plethora of studies on working memory have found that the resources of working memory are extremely limited,and task-irrelevant information(distractors)has a significant impact on the representation of working memory.It is also suggested that inhibition of distractors in working memory is related to alpha oscillation,while the processing of target is related to theta oscillation.However,these are all correlative studies,which cannot confirm the causal role of cortical oscillation for cognitive behavior.In this study,transcranial alternative current stimulation(tACS)and electroencephalography(EEG)were combined to investigate neural oscillation mechanisms for the process to inhibiting distractors in working memory.tACS was delivered with the frequency of 5 Hz(theta band)and 10 Hz(alpha band)over the left or right frontal parietal network.The working memory ‘recall task’ was performed both during(online)and after tACS(offline).There are two levels of distractors in the task,one is the gray squares with less similarity to the target(low level distractor condition,LD),the other is colorful squares with high similarity to the target(high level distractor condition,HD).The results are as below.(1)Both theta and alpha-tACS had effects on the working memory behavior during stimulation,specifically,alpha-tACS enhanced the accuracy of working memory in HD,and theta band weakened the working memory accuracy in HD.(2)Fitting data with Swap model showed that,the main influence of alpha-tACS on working memory performance are as follows: increasing the response probability of target item(Pt)in HD,reducing the response probability of non-target items(Pnt)in HD and reducing random guess probability(Pu)in LD.The influence of theta-tACS on online working memory performance are as follows: reducing Pt in HD,increasing Pnt in HD and reducing Pu in LD.(3)Contralateral Delay Activity(CDA)can be influenced in HD,and alpha-tACS can reduce CDA amplitude,whiletheta-tACS can increase CDA amplitude.(4)Furthermore,alpha and theta-tACS can regulate the corresponding induced oscillation activities,and alpha-tACS can specifically improve alpha power during the memory retention phase;theta-tACS applied on the target side can specifically reduce the contralateral(ipsilateral to distractor)theta power during the stimulus presentation phase.In conclusion,the neural mechanism of working memory is separated in the alpha and theta band oscillations.Alpha-tACS mainly improves alpha power in memory retention phase,enhances the inhibition of distractors in working memory,and then improves the accuracy of working memory.The theta oscillation is mainly responsible for processing the information of working memory,and works together with the alpha oscillation to complete the cognitive processing of working memory.The results of this study provide experimental evidence for the causal relevance of alpha oscillation for inhibition of distractors in working memory.tACS has a significant effect on behavior and suggests the possibility of future clinical application research,which has important scientific significance and application value.