The Effects Of Theta Transcranial Alternating Current Stimulation On Visual Working Memory Performance

Visual working memory is the ability to store and process visual information within a short period of time.Visual working memory ability is closely related to people’s daily life.Studies have shown that visual working memory ability is significantly positively correlated with people’s intelligence,attention and other executive control abilities.Therefore,how to improve the performance of visual working memory has always been a hot topic for researchers.Previous studies have found that transcranial Alternating Current Stimulation（tACS）can significantly improve the performance of individual visual working memory.However,it is unclear whether the improvement in working memory performance is due to the quantity or quality of working memory.This paper explores this issue using a color recall paradigm capable of simultaneously measuring quality and quantity.Experiment 1 applied tACS at 4 Hz and 7 Hz to the right parietal brain regions of participants with high and low working memory capacity to explore the effect of tACS on the quantity and quality of working memory in individuals with different memory capacities.The results showed that the low-frequency theta（4Hz）tACS mainly improved the working memory quality of the participants,while the high-frequency theta（7Hz）tACS mainly decreased the participants’ working memory quantity.The results of this study show that tACS can regulate the theta frequency of the participants and further regulate the memory resources of the participants,providing new experimental evidence for the theta-gamma coupling theory.In addition,cognitive strategies and individual characteristics also influenced participants’ working memory performance when electrical stimulation was applied to modulate participants’ working memory performance.In experiment 2,the low-frequency theta tACS was applied to the right parietal brain region of the participants combined with color recall paradigm,to explore whether different tACS regulation methods would affect individuals’ cognition of their own working memory ability,and then affect the quantity and quality of working memory.The participants were randomly divided into two groups and received different stimulation methods,including first stimulation followed by practice and first practice followed by stimulation.The results of the study replicate the findings of Experiment 1,showing that low-frequency theta tACS can improve the participants’ working memory performance.The participants were then influenced by different cognitive expectations to selectively improve the quantity or quality of their working memory.The results of experiment 2 found that the pre-stimulation group could improve the quantity of participants’ working memory,while the post-stimulation group could improve the quality of participants’ working memory.This suggests that the effect of tACS on working memory performance is mediated by one’s own cognitive expectations.Taken together,different frequencies of theta tACS are able to modulate working memory resources and then selectively affect the quantity and quality of memory representations.Low-frequency theta tACS can increase the participant’s working memory resources,improve the participant’s working memory performance,and further selectively improve the quantity or quality of memory representations.This paper verifies the theta-gamma coupling theory again,which further supplements the experimental evidence for theta-gamma coupling theory.More importantly,individual characteristics,cognitive strategies,and cognitive level expectations may be key factors to consider when exploring the effects of tACS on working memory performance.