Intermittent Theta Burst Stimulation Of The Cerebellar Hemisphere Modulates The Neural Network Related To Swallowing Function Of Healthy Subjects

Objective: To observe the effects of intermittent theta burst stimulation(i TBS)of dominant or non-dominant cerebellar hemisphere in the brain neural network related to swallowing of healthy subjects by using resting-state functional magnetic resonance imaging(rs-f MRI),and to explore the mechanisms of cerebellar i TBS in modulating swallowing function.Methods: In this study,a total of 38 healthy right handed subjects were selected and divided into three groups by random number table method: dominant cerebellum group(i TBS of the dominant cerebellum+sham stimulation of the non-dominant cerebellum,n=13),non-dominant cerebellum group(sham stimulation of the dominant cerebellum+i TBS of the non-dominant cerebellum,n=12),and sham group(sham stimulation of the bilateral cerebellar hemispheres,n=13).Before i TBS,the single-pulse TMS(sp TMS)was used to identify the cerebellar representation of the suprahyoid muscles and to measure resting motor threshold(r MT).And the dominant cerebellar hemisphere for swallowing was determined.Forty-eight hours after elution,i TBS protocols were completed: the i TBS paradigm consisted of bursts of three pulses at 50 Hz repeated at 5 Hz.During i TBS,a 2 s train was followed by an 8 s intermission;this pattern was repeated 20 times for approximately 190s(600 pulses).Rs-f MRI was performed before and after i TBS stimulation to observe changes in the fractional amplitude of low-frequency fluctuation(f ALFF)in the whole brain.Results: Compared to baseline,the dominant cerebellum group showed increased f ALFF in the ipsilateral cerebellum,and decreased f ALFF in the ipsilateral middle temporal gyrus and contralateral precuneus after i TBS,the difference was statistically significant(P<0.05);the i TBS of the non-dominant cerebellum group induced increased f ALFF in the ipsilateral superior frontal gyrus,the calcarine fissure and the surrounding cortex,and the contralateral inferior parietal lobule,the difference was statistically significant(P<0.05);and in the sham group,there was no significant difference in fALFF between baseline and after intervention(P>0.05).In the intergroup comparison,there were no statistically significant differences in f ALFF among the three groups before i TBS(P>0.05).After cerebellar i TBS,there were significant differences in f ALFF values of the contralateral calcarine fissure and the surrounding cortex and ipsilateral middle temporal gyrus among the three groups(P<0.05).Through subsequent post-hoc comparisons,we found that compared with the sham group,the dominant cerebellum group had decreased f ALFF in the contralateral calcarine fissure and the surrounding cortex,the difference was statistically significant(P<0.05);there was no significant difference in f ALFF between the non-dominant cerebellum group and the sham group(P>0.05);and there was no significant difference in f ALFF between the dominant cerebellum group and the non-dominant cerebellum group(P>0.05).Conclusion: Intermittent theta burst stimulation of the dominant cerebellar hemisphere for swallowing excited the ipsilateral cerebellum and caused transient inhibition of some cerebrocortical areas.Stimulation of the non-dominant cerebellar hemisphere increased the spontaneous neural activity of multiple cerebrocortical areas.In conclusion,regardless of which side of the cerebellum is stimulated,i TBS can facilitate part of the brain neural network related to swallowing.These findings provide supporting evidence that cerebellar i TBS is a potential method for regulating human swallowing.