Movement Agency in Functional Movement Disorder Patients and Healthy Individuals

Abstract

Functional movement disorders (FMD) refer to movement abnormalities not being triggered by a neurologic disease [1]. Most common FMD symptom are sudden movements which patients experience involuntary although they are not caused by brain lesions or damage like in other neurological disorders. FMD are a consequence of an issue with how signals are sent throughout the brain and in the brain’s motor centres [2]. It is the function and not physiological lesion causing the disorder.

With this study, our goal is to test the hypothesis that it is more difficult for patients with FMD compared to healthy individuals to distinguish voluntary movement from an involuntary, i.e., a TMS-induced one.

A group of patients with FMD and a group of healthy participants will be investigated using transcranial magnetic stimulation (TMS). Age and gender will differ as little as possible between the two groups. Before the experimental session, for each participant, a hotspot will be measured using neuronavigation method to reduce bias. During the session, participants will be instructed to move a random hand at a set time point and concurrently, TMS will be applied to cause movement in either the same or the opposite hand. Then, volunteers will report on which hand they remember they moved voluntarily, and which was moved by TMS. The experimental design as will mostly be based on Jensen et al. [3].

Our aim is to compare two groups and test for data distribution. Based on the results gained, either parametric or non-parametric tests will be implemented for analysis.

FMD present a large burden in neurology as well as psychiatry and despite their commonness in neurological practice, their prognosis is poor [1]. We hope this study will shed light on movement volition and agency in FMD patients and help for further clinical approach of FMD.

References

[1] T. Pringsheim and M. Edwards, “Functional movement disorders,” Neurology: Clinical Practice, vol. 7, no. 2, pp. 141–147, 2017.doi:10.1212/cpj.0000000000000350

[2] “Functional movement disorders,” Stanford Health Care (SHC) - Stanford Medical Center, https://stanfordhealthcare.org/medical-conditions/brain-and-nerves/functional-movement-disorders.html (accessed May 9, 2023).

[3] M. Jensen, E. Vagnoni, M. Overgaard, and P. Haggard, “Experience of action depends on intention, not body movement: An experiment on memory for Mens Rea,” Neuropsychologia, vol. 55, pp. 122–127, 2014. doi:10.1016/j.neuropsychologia.2013.07.022