Background Patients with functional neurological disorders often report adverse physical events close to the onset of functional symptoms. However, the mechanism via which a triggering event may set off a functional condition is lacking. One possibility is that patients make abnormal inferences about novel information provided by physical triggering events. In this study, the authors aimed to specifically investigate whether patients with functional movement disorders have abnormalities in probabilistic reasoning.
Methods The authors used a well-studied probabilistic reasoning paradigm, ‘the bead task’, in 18 patients with functional movement disorders and 18 healthy agematched controls. The authors assessed the number of beads that participants needed to reach a decision and changes in the certainty of their decisions when confronted with confirmatory or contradictory evidence.
Findings Patients with functional movement disorders requested on average significantly fewer beads before reaching a decision than controls (3 vs 6 beads). When confronted with potentially disconfirmatory evidence, patients showed a significantly greater reduction in confidence in their estimates than controls. 40% of patients reached a decision after one or two beads whereas no controls showed this bias.
Interpretation Patients with functional movement disorders requested less information to form a decision and were more likely to change their probability estimates in the direction suggested by the new evidence. These findings may have relevance to the manner with which patients with functional neurological disorders process novel sensory data occurring during physical triggering events commonly reported at onset of symptoms.
- Functional movement disorders
- ‘jumping to conclusion’ bias
- decision making
- motor control
- motor physiology
- movement disorders
- paroxysmal disorder
- Parkinson's disease
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Funding This work was performed at University College London Hospitals/University College London, which received a proportion of funding from the Department of Health's National Institute for Health Research Biomedical Research Centres Funding Scheme; TAS was supported by a National Institute for Health Research Training Fellowship; MJE was supported by a National Institute for Health Research Clinician Scientist Fellowship.
Correction notice This article has been corrected since it was published Online First. The wrong version of this paper's abstract was originally published and this has now been substituted for the correct one.
Competing interests None.
Ethics approval NHNN/ION Joint Research Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.