Behavioral Differences Across Theta Burst Stimulation Protocols. A Study on the Sense of Agency in Healthy Humans
Abstract
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.
Keywords
theta burst stimulation
30 Hz
50 Hz
sense of agency
behavioral differences Abbreviations: aMT
active motor threshold
APB
abductor pollicis brevis
CI
confidence interval
cTBS
continuous theta burst stimulation
FND
functional neurological disorders
iTBS
intermittent theta burst stimulation
JoA
judgment of agency
JoP
judgment of performance
MEP
motor evoked potentials
MNI
Montreal Neurological Institute
NIBS
noninvasive brain stimulation
rmANOVA
repeated measures analysis of variance
rMT
resting motor threshold
rPPC
right posterior parietal cortex
rTMS
repetitive transcranial magnetic stimulation
rTPJ
right temporo-parietal junction
SAS
summary agency score
SoA
TBS
theta burst stimulation
Domains
Neurons and Cognition [q-bio.NC]| Origin | Publication funded by an institution |
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