Behavioral Differences Across Theta Burst Stimulation Protocols. A Study on the Sense of Agency in Healthy Humans

• Published in: Frontiers in neuroscience Vol. 15; no. 26; p. 658688
• Main Authors: Zito, Giuseppe A., Worbe, Yulia, Lamy, Jean-Charles, Kälin, Joel, Bühler, Janine, Weber, Samantha, Müri, René M., Aybek, Selma
• Format: Journal Article
• Language: English
• Published: Lausanne Frontiers Research Foundation 09.07.2021; Frontiers; Frontiers Media S.A
• Subjects: 30 Hz; 50 Hz; Achievement tests; behavioral differences; Cognitive ability; Cortex (parietal); Life Sciences; Neurons and Cognition; Neuroscience; sense of agency; Synaptic plasticity; theta burst stimulation; Transcranial magnetic stimulation; United States > US; resting motor threshold; SAS; SoA; MNI; active motor threshold; JoP; right temporo-parietal junction; cTBS; 50 Hz; rMT; summary agency score; functional neurological disorders; sense of agency; noninvasive brain stimulation; repetitive transcranial magnetic stimulation; judgment of performance; rPPC; TBS; abductor pollicis brevis; CI; judgment of agency; NIBS; rTPJ; iTBS; behavioral differences Abbreviations: aMT; rmANOVA; intermittent theta burst stimulation; 30 Hz; Montreal Neurological Institute; APB; motor evoked potentials; continuous theta burst stimulation; MEP; repeated measures analysis of variance; right posterior parietal cortex; confidence interval; FND; JoA; rTMS; theta burst stimulation
• ISSN: 1662-453X; 1662-4548; 1662-453X
• DOI: 10.3389/fnins.2021.658688

Background Theta burst stimulation (TBS) is a non-invasive brain stimulation method. Various stimulation protocols have been proposed, for instance, stimulation at 50 Hz with pattern at 5 Hz, or at 30 Hz with pattern at 6 Hz. To identify better stimulation parameters for behavioral applications, we investigated the effects of 50-Hz continuous TBS (cTBS) on the sense of agency (SoA), and compared them with a previously published study with 30-Hz cTBS. Methods Based on power analysis from a previous sample using two applications of 30-Hz cTBS, we recruited 20 healthy subjects in a single-blind, Vertex-controlled, randomized, crossover trial. Participants were stimulated with one application of 50-Hz cTBS over the right posterior parietal cortex (rPPC), a key area for agency processing, and the vertex, in a random order. A behavioral task targeting the SoA was done before and after stimulation. After controlling for baseline differences across samples, we studied the effect of stimulation in the two protocols separately. Results Compared to the previously published 30-Hz protocol, 50-Hz cTBS over the rPPC did not reveal significant changes in the SoA, similar to sham Vertex stimulation. Conclusion One application of 50-Hz cTBS was not sufficient to elicit behavioral effects, compared to two applications of 30-Hz cTBS, as previously described. This may be due to a mechanism of synaptic plasticity, consolidated through consecutive stimulation cycles. Our results are relevant for future studies aiming at modulating activity of the rPPC in cognitive domains other than agency, and in patients affected by abnormal agency, who could benefit from treatment options based on TBS.