title: Dissociation of motor task-induced cortical excitability and pain perception changes in healthy volunteers.
abstract: BACKGROUND
  There is evidence that interventions aiming at modulation of the motor cortex activity lead to pain reduction. In order to understand further the role of the motor cortex on pain modulation, we aimed to compare the behavioral (pressure pain threshold) and neurophysiological effects (transcranial magnetic stimulation (TMS) induced cortical excitability) across three different motor tasks.
  
  
  RESULTS
  Fifteen healthy male subjects were enrolled in this randomized, controlled, blinded, cross-over designed study. Three different tasks were tested including motor learning with and without visual feedback, and simple hand movements. Cortical excitability was assessed using single and paired-pulse TMS measures such as resting motor threshold (RMT), motor-evoked potential (MEP), intracortical facilitation (ICF), short intracortical inhibition (SICI), and cortical silent period (CSP). All tasks showed significant reduction in pain perception represented by an increase in pressure pain threshold compared to the control condition (untrained hand). ANOVA indicated a difference among the three tasks regarding motor cortex excitability change. There was a significant increase in motor cortex excitability (as indexed by MEP increase and CSP shortening) for the simple hand movements.
  
  
  CONCLUSIONS
  Although different motor tasks involving motor learning with and without visual feedback and simple hand movements appear to change pain perception similarly, it is likely that the neural mechanisms might not be the same as evidenced by differential effects in motor cortex excitability induced by these tasks. In addition, TMS-indexed motor excitability measures are not likely good markers to index the effects of motor-based tasks on pain perception in healthy subjects as other neural networks besides primary motor cortex might be involved with pain modulation during motor training.
authors.affiliation: Laboratory of Neuromodulation, Department of Physical Medicine & Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Magdalena S
authors.initials: MS
authors.lastname: Volz
authors.forename: Mariana
authors.initials: M
authors.lastname: Mendonca
authors.forename: Fernando S
authors.initials: FS
authors.lastname: Pinheiro
authors.forename: Huashun
authors.initials: H
authors.lastname: Cui
authors.forename: Marcus
authors.initials: M
authors.lastname: Santana
authors.forename: Felipe
authors.initials: F
authors.lastname: Fregni
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004311:Double-Blind Method; D019054:Evoked Potentials, Motor / Q000502:physiology; D006225:Hand / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D058748:Pain Perception / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult