Exploring the impact of tACS on the neural oscillations involved in speech motor control: a proof-of-concept study

Abstract

<p>Brain oscillations reflect synchronized neuronal activity and are linked to various cognitive and behavioral functions. In motor control, Beta and Alpha band power from the motor cortex is associated with motor planning, differing in individuals with speech motor control deficits like stuttering. This proof-of-concept study aims to investigate the speech motor system's neural networks by applying transcranial alternating current stimulation (tACS) over the speech motor cortex in 20 typically fluent adults and adults who stutter. The goal is to explore whether tACS can entrain Beta and Alpha frequency bands and examine its effects on speech motor planning and execution. The study will compare the effects of single sessions of active tACS at 20 Hz and 6 Hz for 20 minutes to a sham condition over the left premotor cortex, with a one-week interval between sessions. Electrodes will be placed to simultaneously target the left supplementary motor area and left inferior frontal gyrus for cortical oscillation entrainment. Resting-state EEG will be recorded for five minutes before and after tACS to monitor changes in neural oscillations. Participants will complete a sentence completion task requiring to produce a direct object (e.g., The man drinks a__), with a preparation time of 800-1000 milliseconds. EEG recordings during the task performance will be conducted to detect changes in neural oscillations, and response times and accuracy will be measured after stimulation. Additionally, an oral diadochokinetic task will assess the impact of stimulation on speech motor execution. This research provides insights into intact and impaired speech motor systems, such as stuttering, and contributes to the development of neuroscience-based intervention methods in the future.<br></p>