title: Aversive stimuli exacerbate defensive motor behaviour in motor conversion disorder.
abstract: Conversion disorder or functional neurological symptom disorder (FND) can affect the voluntary motor system, without an organic cause. Functional symptoms are thought to be generated unconsciously, arising from underlying psychological stressors. However, attempts to demonstrate a direct relationship between the limbic system and disrupted motor function in FND are lacking. We tested whether negative affect would exacerbate alterations of motor control and corresponding brain activations in individuals with FND. Ten patients and ten healthy controls produced an isometric precision-grip contraction at 10% of maximum force while either viewing visual feedback of their force output, or unpleasant or pleasant emotional images (without feedback). Force magnitude was continuously recorded together with change in brain activity using fMRI. For controls, force output decayed from the target level while viewing pleasant and unpleasant images. Patients however, maintained force at the target level without decay while viewing unpleasant images, indicating a pronounced effect of negative affect on force output in FND. This emotional modulation of force control was associated with different brain activation patterns between groups. Contrasting the unpleasant with the pleasant condition, controls showed increased activity in the inferior frontal cortex and pre-supplementary motor area, whereas patients had greater activity in the cerebellum (vermis), posterior cingulate cortex, and hippocampus. Engagement of a cerebellar-limbic network in patients is consistent with heightened processing of emotional salience, and supports the role of the cerebellum in freezing responses in the presence of aversive events. These data highlight a possible neural circuit through which psychological stressors elicit defensive behaviour and modulate motor function in FND.
authors.affiliation: Laboratory for Behavioral Neurology and Imaging of Cognition, Department of Neuroscience, University of Geneva, Switzerland; Swiss Center for Affective Sciences, University of Geneva, Switzerland. Electronic address: rebekah.blakemore@otago.ac.nz.
authors.forename: Rebekah L
authors.initials: RL
authors.lastname: Blakemore
authors.affiliation: Laboratory for Behavioral Neurology and Imaging of Cognition, Department of Neuroscience, University of Geneva, Switzerland; Swiss Center for Affective Sciences, University of Geneva, Switzerland; Service of General Psychiatry, Department of Psychiatry and Mental Health, University Hospitals of Geneva, Switzerland. Electronic address: Indrit.Sinanaj@unige.ch.
authors.forename: Indrit
authors.initials: I
authors.lastname: Sinanaj
authors.affiliation: Department of Neurology, University of Franche-Comté, Besançon, France. Electronic address: galli.silvio@hotmail.fr.
authors.forename: Silvio
authors.initials: S
authors.lastname: Galli
authors.affiliation: Laboratory for Behavioral Neurology and Imaging of Cognition, Department of Neuroscience, University of Geneva, Switzerland. Electronic address: Selma.Aybek@unige.ch.
authors.forename: Selma
authors.initials: S
authors.lastname: Aybek
authors.affiliation: Laboratory for Behavioral Neurology and Imaging of Cognition, Department of Neuroscience, University of Geneva, Switzerland; Swiss Center for Affective Sciences, University of Geneva, Switzerland; Department of Neurology, University Hospitals of Geneva, Switzerland. Electronic address: Patrik.Vuilleumier@unige.ch.
authors.forename: Patrik
authors.initials: P
authors.lastname: Vuilleumier
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D003291:Conversion Disorder / Q000503:physiopathology* / Q000523:psychology; D004644:Emotions / Q000502:physiology*; D030141:Feedback, Psychological / Q000502:physiology*; D005260:Female; D018737:Hand Strength; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009483:Neuropsychological Tests; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Cerebellum vermis; Emotion; Force control; Freezing; Functional symptoms