Modulation Of Verbal Fluency By Transcranial Alternating Current Stimulation

Verbal fluency is a cognitive function that facilitates knowledge retrieval in memory.It describes how fluently an individual uses language to convey information,it is an important indicator of human verbal ability.Transcranial alternating current stimulation（tACS）is a non-invasive neurostimulation technique in which weak,periodically varying electrical currents are applied to specific areas of the brain.It has been shown to modulate the excitatory activity of the cerebral cortex.The tACS technique has been shown to have positive effects on language ability.Therefore,this article proposes to investigate the attenuating effect of the tACS technique on verbal fluency by combining the tACS technique and verbal fluency.This thesis consists of two main studies as follows: the main purpose of Study 1 is to investigate the modulatory effects of transcranial alternating current stimulation of the left prefrontal lobe on verbal fluency.In this study,we administered 10 Hz tACS stimulation,40 Hz tACS stimulation,and sham stimulation on the prefrontal cortex to12 healthy subjects,and then asked them to complete a phonemic fluency task and a semantic fluency task.The results showed that 10-Hz tACS significantly improved phonemic fluency,including the number of words produced and the speed of response to reach a fixed word,but tACS did not have an effect on the semantic fluency task.The main purpose of Study 2 is to investigate the effects of tACS at different alpha frequencies on verbal fluency.In the present study,we respectively performed 8Hz tACS stimulation,10 Hz tACS stimulation,and 12 Hz tACS stimulation on the prefrontal cortex.The results showed that 8-Hz tACS significantly improved the subjects’ phonemic fluency and semantic fluency,including the number of words produced and the speed of response to reach a fixed word,compared to 10-Hz stimulation.Combining the experimental results of Study 1 and Study 2,the main findings of this thesis are as follows: first,our study demonstrated the specific effect of tACS in improving verbal fluency（both phonemic fluency and semantic fluency）;second,it demonstrated that the effect of different frequencies of tACS on verbal fluency was different,the alpha band had a significant modulating effect on verbal fluency.