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Reduced drift rate: a biomarker of impaired information processing in functional movement disorders.

Sadnicka, A; Daum, C; Meppelink, A-M; Manohar, S; Edwards, M (2020) Reduced drift rate: a biomarker of impaired information processing in functional movement disorders. Brain, 143 (2). pp. 674-683. ISSN 1460-2156 https://doi.org/10.1093/brain/awz387
SGUL Authors: Sadnicka, Anna

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Abstract

Functional neurological disorder is a common and phenomenologically diverse condition. Resultant disability is caused by both the dominant clinical presentation, e.g. paralysis or tremor and additional symptomatology such as cognitive symptoms. Recently the similarity of neuropsychiatric profiles across a range of functional syndromes has been highlighted. This is suggestive of a common underlying mechanism with a theoretical deficit of information processing proposed. Identification of an experimental biomarker for such deficits could offer novel assessment and therapeutic strategies. In this study, we took the temporal discrimination threshold as a paradigm that can be used to model sensory processing in functional movement disorders. Our hypothesis was that we would be able to delineate markers of slowed information processing in this paradigm removed from the phenomenological presentation with a movement disorder. We recorded both response accuracy and reaction time in a two-choice temporal resolution/discrimination task in 36 patients with functional movement disorders and 36 control subjects. A psychometric function was fitted to accuracy data for each individual revealing both abnormally high threshold values (P = 0.0053) and shallow psychometric slopes in patients (P = 0.0015). Patients with functional movement disorders also had significantly slower response times (P = 0.0065). We then used a well-established model for decision-making (the drift diffusion model) that uses both response accuracy and reaction time data to estimate mechanistic physiological dimensions of decision-making and sensory processing. This revealed pathologically reduced drift rate in the patient group, a parameter that quantifies the quality and rate of information accumulation within this sensory task (P = 0.002). We discuss how the deficits we observed in patients with functional movement disorders are likely to stem from abnormal allocation of attention that impairs the quality of sensory information available. Within a predictive coding framework sensory information could be down-weighted in favour of predictions encoded by the prior. Our results therefore offer a parsimonious account for a range of experimental and clinical findings. Reduced drift rate is a potential experimental marker for a generalized deficit in information processing across functional disorders that allows diverse symptomatology to be quantified under a common disease framework.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced version of an article accepted for publication in Brain following peer review. The version of record Anna Sadnicka, Corinna Daum, Anne-Marthe Meppelink, Sanjay Manohar, Mark Edwards, Reduced drift rate: a biomarker of impaired information processing in functional movement disorders, Brain, Volume 143, Issue 2, February 2020, Pages 674–683 is available online at: https://doi.org/10.1093/brain/awz387
Keywords: biomarker, decision modelling, functional neurological disorder, psychogenic, temporal discrimination threshold, Neurology & Neurosurgery, 11 Medical and Health Sciences, 17 Psychology and Cognitive Sciences
SGUL Research Institute / Research Centre: Academic Structure > Molecular and Clinical Sciences Research Institute (MCS)
Journal or Publication Title: Brain
ISSN: 1460-2156
Language: eng
Dates:
DateEvent
February 2020Published
22 December 2019Published Online
17 October 2019Accepted
Publisher License: Publisher's own licence
PubMed ID: 31865371
Go to PubMed abstract
URI: http://openaccess.sgul.ac.uk/id/eprint/111522
Publisher's version: https://doi.org/10.1093/brain/awz387

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