title: Electrophysiological correlates of disobedience and feigning-like behaviour in motor imagery.
abstract: OBJECTIVE
  To explore motor excitability changes induced by disobedience and feigning-like behaviour.
  
  
  METHODS
  Healthy subjects participated in motor imagery tasks. They imagined either a maximum muscle relaxation (condition 1) or a pinch grip (condition 2). In other trials, they were instructed to disobey the command to imagine a pinch grip. Instead, they should either imagine a maximum muscle relaxation (condition 3) or think of something else which they could choose freely (condition 4). Transcranial magnetic stimulation was used to explore motor excitability during the different tasks. Motor evoked potential amplitudes were expressed as percentage of the task-free control condition (condition 5).
  
  
  RESULTS
  Imagination of a pinch grip enhanced motor excitability, imagery of maximum muscle relaxation reduced motor excitability below the level of the control condition. In conditions 3 and 4, motor excitability was lower than in condition 2. However, motor excitability in condition 3 was higher than in condition 1.
  
  
  CONCLUSIONS
  Healthy subjects successfully disobeyed the motor imagery command but failed to maintain the down-regulation of motor excitability when trying to imagine maximum muscle relaxation.
  
  
  CONCLUSIONS
  The results help to interpret the down-regulation of motor excitability found in patients with motor conversion disorder.
authors.affiliation: Department of Neurorehabilitation, Klinken Schmieder, Allensbach, Germany. Electronic address: j.liepert@kliniken-schmieder.de.
authors.forename: Joachim
authors.initials: J
authors.lastname: Liepert
authors.affiliation: Department of Neurosurgery, University Hospital Tübingen, Germany.
authors.forename: Januz
authors.initials: J
authors.lastname: Shala
authors.affiliation: Department of Neurorehabilitation, Klinken Schmieder, Allensbach, Germany.
authors.forename: Johanna
authors.initials: J
authors.lastname: Greiner
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007092:Imagination / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D009126:Muscle Relaxation / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods
keywords: Disobedience; Feigning-like behaviour; Motor imagery; Transcranial magnetic stimulation