A Mechanistic Investigation of Cerebellar Intermittent Theta-Burst Stimulation-Induced Changes in Pharyngeal Motor...

Previous studies have shown that intermittent theta burst stimulation (iTBS) can promote the recovery of swallowing function in stroke patients. However, the therapeutic mechanism is not well understood. No study has elucidated the swallowing mechanism of iTBS and its cortical excitability changes in controlled healthy samples. Changes in cortical excitability can reflect the improvement of swallowing function. The purpose of this study was to observe the activation of the cerebral cortex during voluntary swallowing in healthy adults and to investigate the direct effect of cerebellar iTBS on the excitability of the pharyngeal motor cortex, to explore further the potential mechanisms by which cerebellar iTBS improves swallowing function. Thirty healthy subjects were recruited for this study and randomized to left and right cerebellar iTBS stimulation. The order of stimulation of the left and right cerebellum was randomized, and the stimulation interval was approximately one week. Functional near-infrared spectroscopy (fNIRS) was used to assess brain activation before and after iTBS stimulation and the parameter "β-value." fNIRS was paradigmatized as a classical block task, and the whole procedure consisted of three identical blocks, each consisting of a 30-s swallowing task and a 30-s rest period. Bilateral superior temporal gyrus (STG), middle temporal gyrus (MTG), primary motor cortex (PMC), pre-motor and supplementary motor cortex (PSMC), primary somatosensory cortex (PSC), pars triangularis (PTG), frontopolar area (FPA), frontal eye fields (FEF), and dorsolateral prefrontal area (DLPFC)were significantly activated during the performance of a voluntary swallowing task. Compared with pre-stimulation, the beta values significantly increased in channels 5 (P = 0.013), 17 (P = 0.025), 18 (P = 0.027), 19 (P = 0.046), 34 (P = 0.045), and 37(P = 0.045) after left cerebellar stimulation; After cerebellar right side stimulation, the beta values significantly increased in channels 3 (P = 0.043), 18 (P = 0.022), 20 (P = 0.047), 38 (P = 0.032), 46 (P = 0.028), and 48 (P = 0.028). Bilateral STG, MTG, PMC, PSMC, PSC, PTG, FPA, FEF, and DLPFC were involved in regulating volitional swallowing. Both iTBS to the left and right cerebellum significantly increased the excitability of swallowing cortical areas under a swallowing-specific task.