title: Deficit in late-stage contingent negative variation provides evidence for disrupted movement preparation in patients with conversion paresis.
abstract: Conversion paresis is the presence of unexplained weakness without detectable neuropathology that is not feigned. To examine the 'abnormal preparation' and 'disrupted execution' hypotheses proposed to explain the movement deficits in conversion paresis, electroencephalographic, electromyographic and kinematic measures were recorded during motor preparation and execution. Six patients with unilateral upper limb conversion weakness, 24 participants feigning weakness and 12 control participants performed a 2-choice precued reaction time task. Precues provided advance information about the responding hand or finger. Patients and feigners demonstrated similar diminished force, longer movement time and extended duration of muscle activity in their symptomatic limb. Patients showed significantly suppressed contingent negative variation (CNV) amplitudes, but only when the symptomatic limb was precued. Despite the similarity in performance measures, this CNV suppression was not seen in feigners. Diminished CNV for symptomatic hand precues may reflect engagement of an inhibitory mechanism suppressing cortical activity related to preparatory processes.
authors.affiliation: School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin 9016, New Zealand; Brain Health Research Centre, University of Otago, Dunedin 9016, New Zealand. Electronic address: rebekah.blakemore@otago.ac.nz.
authors.forename: Rebekah L
authors.initials: RL
authors.lastname: Blakemore
authors.affiliation: Department of Physiology, University of Otago, Dunedin 9016, New Zealand; Brain Health Research Centre, University of Otago, Dunedin 9016, New Zealand. Electronic address: brian.hyland@otago.ac.nz.
authors.forename: Brian I
authors.initials: BI
authors.lastname: Hyland
authors.affiliation: Department of Medicine, University of Otago, Dunedin 9016, New Zealand; Brain Health Research Centre, University of Otago, Dunedin 9016, New Zealand. Electronic address: graeme.hammond-tooke@southerndhb.govt.nz.
authors.forename: Graeme D
authors.initials: GD
authors.lastname: Hammond-Tooke
authors.affiliation: Department of Sport and Exercise Science, and Centre for Brain Research, University of Auckland, Auckland 1142, New Zealand. Electronic address: g.anson@auckland.ac.nz.
authors.forename: J Greg
authors.initials: JG
authors.lastname: Anson
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D003265:Contingent Negative Variation / Q000502:physiology*; D003291:Conversion Disorder / Q000503:physiopathology*; D004569:Electroencephalography; D004576:Electromyography; D005260:Female; D005385:Fingers / Q000502:physiology; D006225:Hand / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D010291:Paresis / Q000503:physiopathology* / Q000523:psychology; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology
keywords: Contingent negative variation; Conversion disorder; Electromyography; Feigning; Functional paresis; Motor preparation