Raised visual contrast thresholds with intact attention and metacognition in functional motor disorder.

Functional motor disorders (FMDs) are distinguished by signs that lack congruence with recognised patterns of organic disease and show inconsistency over time. Their pathophysiology is poorly understood, but there is evidence that irregularities in perceptual and cognitive processing lie at the heart of these conditions. Here, we draw on a predictive coding account of functional neurological disorders to study perceptual decision-making in three groups: 20 patients with FMDs (14 with functional movements and 6 with functional weakness), 20 with phenotypically-matched organic motor disorders, and 20 age-matched healthy controls. We examine four cognitive domains with putative roles in FMD pathogenesis: attention, expectations, sensory processing (perceptual sensitivity), and metacognition (introspective evaluation of performance). We augmented a dual-task paradigm, manipulating the visual contrast required for target detection to examine these domains in one design. With sensory input (stimulus contrast) psychometrically adjusted to staircase target detection at a fixed level for all groups, the FMD group exhibited statistically equivalent attentional, expectational and metacognitive processing to healthy controls. However, we demonstrate Bayesian evidence and a frequentist trend that FMD patients require higher visual contrast than controls to maintain the same detection sensitivity (BF

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Declaration of Competing Interest We declare we have no competing interests.