The Effect of Transcutaneous Occipital Nerve Stimulation on a Core Brain Network via Functional Connectivity
Yoo, Hye Bin
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Transcutaneous electrical stimulation of the greater occipital nerve (ON-tES) has been clinically successful for ameliorating various chronic disorders, but the mechanism underlying its efficacy is unclear. This study aims at investigating its effect on the brain in terms of functional connectivity, focusing especially on changes within the default mode network (DMN) that is implied in processing self-related information and updating the internal reference point. Employing resting state functional magnetic resonance imaging, the differences in connectivity measures are evaluated across pre-, during-, and post-stimulation periods using a single-blinded, parallel study design. Two representative measures are used: static functional connectivity and dynamic connection variability. ON-tES was found to alter the DMN based on both measures. Static connectivity increased, and dynamic connection variability decreased, in particular during stimulation. This result suggests that ON-tES instantaneously enhances and stabilizes the functions of the DMN. Further investigation aimed to specify the roles of the anterior and posterior subdivisions of the DMN using ON-tES. The static functional connectivity of posterior DMN increased during stimulation and persisted after stimulation, but its dynamic connection variability did not alter by stimulation. The static functional connectivity of anterior DMN was not affected by the stimulation, but its dynamic connection variability decreased significantly during stimulation. The functional enhancement of posterior DMN may be important for the long-term effect of ON-tES, whereas the stabilization of anterior subdivision may be a dominant factor in the instantaneous effect of the stimulation. This study addresses for the first time the changes in both static and dynamic connectivity due to ON-tES. The present findings elucidate how the working mechanism of ON-tES relates to the reconstruction of a sound internal reference managed by the DMN. The results of this study will prove useful in guiding future clinical applications of ON-tES.