Giuseppe A. Zito, PhD; Laura B. Anderegg, MD; Kallia Apazoglou, PhD; René M. Müri, MD; Roland Wiest, MD; Martin grosse Holtforth, PhD; Selma Aybek, MD
Background: The sense of agency is an important aspect of motor control. Impaired sense of agency has been linked to several medical conditions, including schizophrenia and functional neurological disorders. A complex brain network subserves the sense of agency, and the right temporoparietal junction is one of its main nodes. In this paper, we tested whether transcranial magnetic stimulation over the right temporoparietal junction elicited behavioural changes in the sense of agency.
Methods: In experiment 1, 15 healthy participants performed a behavioural task during functional MRI, with the goal of localizing the area relevant for the sense of agency in the right temporoparietal junction. In the task, the movement of a cursor (controlled by the participants) was artificially manipulated, and the sense of agency was either diminished (turbulence) or enhanced (magic). In experiment 2, we applied transcranial magnetic stimulation in 20 healthy participants in a sham-controlled, crossover trial with excitatory, inhibitory or sham (vertex) stimulation. We measured the summary agency score, an indicator of the sense of agency (lower values correspond to diminished sense of agency).
Results: Experiment 1 revealed a peak of activation during agency manipulation in the right temporoparietal junction (Montreal Neurological Institute coordinates x, y, z: 68, −26, 34). Experiment 2 showed that inhibition of the right temporoparietal junction significantly reduced the summary agency score in both turbulence (from −14.4 ± 11.4% to −22.5 ± 8.9%), and magic (from −0.7 ± 5.8% to −4.4 ± 4.4%).
Limitations: We found no excitatory effects, possibly because of a ceiling effect (because healthy participants have a normal sense of agency) or noneffectiveness of the excitatory protocol.
Conclusion: Our experiments showed that the network subserving the sense of agency was amenable to neuromodulation in healthy participants. This sets the ground for further research in patients with impaired sense of agency.
Clinical trial identification: DRKS00012992 (German clinical trials registry).
Submitted May 21, 2019; Revised Oct. 9, 2019; Accepted Nov. 11, 2019; Published online Apr. 24, 2020
Acknowledgements: The authors acknowledge the Swiss National Science Foundation (SNSF), the Fondation Leenaards, the University Hospital Inselspital Bern and the University of Bern for their support and thank all the study participants.
Affiliations: From the Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Switzerland (Zito, Anderegg, Müri, Holtforth, Aybek); the Support Centre for Advanced Neuroimaging (SCAN), University Institute for Diagnostic and Interventional Neuroradiology, Inselspital, Bern University Hospital, University of Bern, Switzerland (Zito, Wiest); Department of Neuroscience, Faculty of Medicine, University of Geneva, Switzerland (Apazoglou); the Perception and Eye Movement Laboratory, Department of Neurology and Biomedical Research, Inselspital, Bern University Hospital, University of Bern, Switzerland (Müri); and the Institute of Psychology, University of Bern, Bern, Switzerland (Holtforth).
Competing interests: R. Müri declares funding from the Swiss National Foundation, outside of the submitted work. No other competing interests were declared.
Contributors: G. Zito, R. Müri, R. Wiest, M. Holtforth and S. Aybek designed the study. G. Zito and L. Anderegg acquired the data, which G. Zito, K. Apazoglou, R. Müri, R. Wiest, M. Holtforth and S. Aybek analyzed. G. Zito and S. Aybek wrote the article, which all authors reviewed. All authors approved the final version to be published and can certify that no other individuals not listed as authors have made substantial contributions to the paper.
Correspondence to: G.A. Zito, Support Centre for Advanced Neuroimaging (SCAN), University Institute for Diagnostic and Interventional Neuroradiology, Department of Neurology, Bern University Hospital Inselspital, Sahli Haus 1, Freiburgstrasse, CH-3010 Bern, Switzerland; email@example.com