Response inhibition in patients with functional neurological symptom disorder.

Abnormal response inhibition has been demonstrated in psychogenic movement disorders (PMD) and is a plausible mechanism for other forms of functional neurological symptom disorder (FNSD), in which response inhibition has not yet been investigated. Response inhibition was therefore studied in patients with FNSD, including patients with psychogenic non-epileptic seizures (PNES), functional weakness (FW) or both. Twenty-nine patients with FNSD and 29 age and sex-matched healthy volunteers underwent a go-nogo task, a stop-signal reaction time (SSRT) task, and a negative priming flanker task. The Attentional Resource Allocation Scale, the Beck Depression Inventory and the Spielberger State and Trait Anxiety Inventory were also administered. Mean hit rates on nogo trials, miss rates on go signals and discriminability index were higher and go signal reaction times were significantly longer in the FNSD group than in healthy controls. The presence of FW was associated with increased hit rates on nogo trials, suggesting a bias toward responding to nogo signals rather than missed go signals. SSRT and negative priming were not significantly different from healthy controls. It is unclear whether impaired performance on the go-nogo task reflects dysfunctional inhibitory processes, disordered attention, or impaired ability to discriminate between stimuli.