Interhemispheric facilitation of gesturing: A combined theta burst stimulation and diffusion tensor imaging study

Abstract

Background: Imaging studies point to a posture (finger vs. hand) and domain-specific neural basis of gestures. Furthermore, modulation of gestures by theta burst stimulation (TBS) may depend on interhemispheric disinhibition. Objective/Hypothesis: In this randomized sham-controlled study, we hypothesized that dual site continuous TBS over left inferior frontal gyrus (IFG-L) and right inferior parietal gyrus (IPL-R) predominantly affects pantomime of finger postures. Furthermore, we predicted that dual cTBS improves imitation of hand gestures if the effect correlates with measures of callosal connectivity. Methods: Forty-six healthy subjects participated in this study and were targeted with one train of TBS in different experimental sessions: baseline, sham, single site IFG-L, dual IFG-L/IPL-R, single site IPL-R. Gestures were evaluated by blinded raters using the Test for Upper Limb Apraxia (TULIA) and Postural Imitation Test (PIT). Callosal connectivity was analyzed by diffusion tensor imaging (DTI). Results: Dual cTBS significantly improved TULIA total (F [3, 28] ¼ 4.118, p ¼ .009), but did not affect TULIA pantomime. The beneficial effect was driven by the cTBS over IPL-R, which improved TULIA imitation (p ¼ .038). Furthermore, TULIA imitation significantly correlated with the microstructure (fractional anisotropy) of the splenium (r ¼ 0.420, p ¼ .026), corrected for age and whole brain volume. Conclusions: The study suggests that inhibition of IPL-R largely accounted for improved gesturing, possibly through transcallosal facilitation of IPL-L. Therefore, the findings may be relevant for the treatment of apraxic stroke patients. Gesture pantomime and postural gestures escaped the modulation by dual cTBS, suggesting a more widespread and/or variable neural representation.

Dysbalanced Resting-State Functional Connectivity Within the Praxis Network Is Linked to Gesture Deficits in Schizophrenia

“…The IFG is an important brain area for gesture in healthy subjects, lesion studies, and in schizophrenia. 13-15 , 18 , 22 , 23 , 68 For example, we have reported lower GM volume and cortical thickness of left IFG in patients with gesture deficit compared with controls in the present sample. 20 , 21 Patients also showed hypoactivation in bilateral IFG during planning of gestures.…”

Perspectives on Rehabilitation Using Non-invasive Brain Stimulation Based on Second-Person Neuroscience of Teaching-Learning Interactions

“…Vanbellingen et al investigated whether dual-site stimulation, which consists of left IFG stimulation immediately followed by right IPL stimulation, modulated the imitation process. The results indicated that dual-site stimulation using continuous theta bursts enhanced the performance of gesture imitation compared with sham or left IFG stimulation ( Vanbellingen et al, 2020 ). Consequently, the tACS approach to brain communication has attracted attention for modulating the imitation process.…”

Brain Stimulation and Group Therapy to Improve Gesture and Social Skills in Schizophrenia—The Study Protocol of a Randomized, Sham-Controlled, Three-Arm, Double-Blind Trial

“…A pilot study demonstrated that inhibitory cTBS over the right inferior parietal lobe (rIPL) improved gesture performance by comparing 3 rTMS protocols (including sham stimulation) in 20 patients ( 48 ). Due to interhemispheric rivalry, cTBS on the right IPL may induce a facilitatory effect on left IPL through transcallosal disinhibition ( 50 ). As such, inhibitory cTBS over the rIPL is a promising method to reduce gesture deficits in schizophrenia.…”