The relationship between sense of agency and sense of ownershipparameters and clinical features in patients with functional movement disorders

This cross-sectional study investigates the disturbance of sense of agency and sense of ownership, which are thought to play a role in the pathophysiology of Functional Movement Disorder (FMD), and examines the relationship of these parameters with the functional symptom severity and psychological traits which are believed to be the presidposing and sustaining factors of the disorder. The study includes 30 patients aged between 18-65 and 30 age- matched, sex-matched, education-matched healthy controls. The Structured Clinical Interview for DSM-5 (SCID-5), Toronto Alexithymia Scale (TAS), Symptom Checklist-90 (SCL-90), Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), Traumatic Experiences Scale (TES), Childhood Trauma Questionnaire (CTQ), Chalder Fatigue Scale (CFS), and Dissociative Experiences Scale (DES) were applied to all participants. Additionally, the Illness Perception Questionnaire (IPQ) and the Functional Movement Disorder Rating Scale (FMDRS) were applied to the patient group. Implicit sense of agency was examined through the "Intentional Binding Task," while sense of ownership was examined through the "Rubber Hand Illusion Task." The FMD group showed significantly lower overall binding scores, as well as action binding and outcome binding scores compared to healthy control group. No significant difference was found between the two groups in terms of the subjective and objective measurements of sense of ownership. The FMD group had significantly higher scores on TAS, BDI, BAI, SCL-90, CFS, TES, and DES scales compared to the control group. Emotional neglect sub-scale scores from the CTQ were higher in the patient group, while no difference was found in the other sub-scales of CTQ. No correlation was found between sense of ownership and sense of agency parameters with symptom severity or other clinical variables. These results suggest that the sense of agency was reduced in FMD patients compared to healthy controls while the sense of ownership is preserved. The finding that the reduced sense of agency in the FMD group is not correlated with symptom severity or other psychological traits suggests that the reduction in sense of agency may play an independent and persistent role in the pathophysiology as a trait, rather than being influenced by symptom severity or predisposing psychological traits. Further studies with larger samples and longitudinal designs will be beneficial to investigate the role of reduced sense of agency in the pathophysiology of FMD patients.