title: Modulatory effects of transcranial direct current stimulation on laser-evoked potentials.
abstract: OBJECTIVE
  Invasive stimulation of the motor cortex has been used for years to alleviate chronic intractable pain in humans. In our study, we have investigated the effect of transcranial direct current stimulation (tDCS), a noninvasive stimulation method, for manipulating the excitability of cortical motor areas on laser evoked potentials (LEP) and acute pain perception. DESIGNS AND SETTINGS: The amplitude of the N1, N2, and P2 LEP components of 10 healthy volunteers were evaluated prior to and following anodal, cathodal, and sham stimulation of the primary motor cortex. In a separate experiment subjective, pain rating scores of 16 healthy subjects in two perceptual categories (warm sensation, mild pain) were also analyzed.
  
  
  RESULTS
  Cathodal tDCS significantly reduced the amplitude of N2 and P2 components compared with anodal or sham stimulation. However, neither of the tDCS types modified significantly the laser energy values necessary to induce moderate pain. In a separate experiment, cathodal stimulation significantly diminished mild pain sensation only when laser-stimulating the hand contralateral to the side of tDCS, while anodal stimulation modified warm sensation.
  
  
  CONCLUSIONS
  The possible underlying mechanisms of our findings in view of recent neuroimaging studies are discussed. To our knowledge this study is the first to demonstrate the mild antinociceptive effect of tDCS over the primary motor cortex in healthy volunteers.
authors.affiliation: Department of Clinical Neurophysiology, Georg-August University, Göttingen, Germany.
authors.forename: Gabor
authors.initials: G
authors.lastname: Csifcsak
authors.forename: Andrea
authors.initials: A
authors.lastname: Antal
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Hillers
authors.forename: Maik
authors.initials: M
authors.lastname: Levold
authors.forename: Cornelius G
authors.initials: CG
authors.lastname: Bachmann
authors.forename: Svenja
authors.initials: S
authors.lastname: Happe
authors.forename: Michael A
authors.initials: MA
authors.lastname: Nitsche
authors.forename: Jens
authors.initials: J
authors.lastname: Ellrich
authors.forename: Walter
authors.initials: W
authors.lastname: Paulus
mesh_terms: D000328:Adult; D000818:Animals; D004558:Electric Stimulation / Q000379:methods*; D004569:Electroencephalography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007834:Lasers; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D059408:Pain Management; D011597:Psychomotor Performance; D012677:Sensation / Q000502:physiology; D012684:Sensory Thresholds; D055815:Young Adult