title: Enhanced mirror activity in 'crossed' reaction time tasks in multiple sclerosis.
abstract: OBJECTIVE
  Execution of unimanual voluntary motor tasks requires appropriate inhibitory control over contralateral motor output. Such inhibition should involve interhemispheric connections, which are often damaged in multiple sclerosis (MS).
  
  
  METHODS
  Twenty mildly-disabled MS patients and 13 healthy subjects performed ipsilateral and contralateral wrist-extension reactions (IR and CR, respectively) to a unilateral somatosensory cue, the latter condition requiring necessarily interhemispheric transfer of information. Prevalence, persistence, latency and amount of mirror electromyographic activity (mEMG) were calculated in each study group, as well as diffusion-tensor-imaging measures of damage in corpus callosum and brainstem for correlation with mEMG.
  
  
  RESULTS
  Healthy subjects and patients showed mEMG more often in CR than in IR. In CR tasks, mEMG was larger, more persistent and occurred more often at a shorter latency with respect to voluntary reaction in patients than in healthy subjects (p<0.05 for all). Patients with mEMG had significantly higher diffusivity values of damage in corpus callosum and lower brainstem volumes than patients without mEMG (p<0.05 for all).
  
  
  CONCLUSIONS
  MS patients show deficient inhibition of unintended mEMG in 'crossed' reaction time tasks.
  
  
  CONCLUSIONS
  Enhanced mEMG in MS may be due to microstructural axonal damage and atrophy in inhibitory commissural connections of the corpus callosum and brainstem.
authors.affiliation: EMG Unit, Neurology Department, Hospital Clinic, Barcelona, Spain. Electronic address: ccabibitalia@yahoo.it.
authors.forename: Christopher
authors.initials: C
authors.lastname: Cabib
authors.affiliation: Center for Neuroimmunology, Neurology Department, Hospital Clínic, Barcelona, Spain; IDIBAPS (Institut d'Investigació August Pi i Sunyer), Facultat de Medicina, University of Barcelona, Barcelona, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Llufriu
authors.affiliation: Center for Neuroimmunology, Neurology Department, Hospital Clínic, Barcelona, Spain; IDIBAPS (Institut d'Investigació August Pi i Sunyer), Facultat de Medicina, University of Barcelona, Barcelona, Spain.
authors.forename: Eloy
authors.initials: E
authors.lastname: Martinez-Heras
authors.affiliation: Center for Neuroimmunology, Neurology Department, Hospital Clínic, Barcelona, Spain; IDIBAPS (Institut d'Investigació August Pi i Sunyer), Facultat de Medicina, University of Barcelona, Barcelona, Spain.
authors.forename: Albert
authors.initials: A
authors.lastname: Saiz
authors.affiliation: EMG Unit, Neurology Department, Hospital Clinic, Barcelona, Spain; IDIBAPS (Institut d'Investigació August Pi i Sunyer), Facultat de Medicina, University of Barcelona, Barcelona, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Valls-Solé
mesh_terms: D000328:Adult; D001933:Brain Stem / Q000503:physiopathology; D003337:Corpus Callosum / Q000503:physiopathology; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000175:diagnosis* / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology
keywords: Crossed reaction time tasks; Interhemipheric connections; Mirror electromyographic activity; Mirror movements; Motor control; Multiple sclerosis