title: Increasing human leg motor cortex excitability by transcranial high frequency random noise stimulation.
abstract: OBJECTIVE
  Transcranial random noise stimulation (tRNS) can increase the excitability of hand area of the primary motor cortex (M1). The aim of this study was to compare the efficacy of tRNS and transcranial direct current stimulation (tDCS) on the leg motor cortex.
  
  
  METHODS
  Ten healthy subjects received anodal, cathodal tDCS, tRNS and sham stimulation for 10 min using 2 mA intensity during separate experimental sessions. Single pulse transcranial magnetic stimulation (TMS) induced motor evoked potential (MEP) measurements were used to assess motor cortical excitability changes after the stimulation.
  
  
  RESULTS
  Similar to the hand area, we found that both tRNS and anodal tDCS induced an increase of the amplitude of the MEPs. Anodal tDCS induced a constant gradual increase of corticospinal excitability until 60 min post-stimulation, whereas the effect of tRNS was immediate with a duration of 40 min following stimulation. The cathodal tDCS induced decrease in MEP amplitude did not reach statistical significance.
  
  
  CONCLUSIONS
  Our results suggest that although the leg area has a deeper position in the cortex compared to the hand area, it can be reached by weak transcranial currents. Both anodal tDCS and tRNS had comparable effect on cortical excitability.
authors.affiliation: Department of Neurology, Albert Szent-Györgyi University of Szeged, Szeged, Hungary.
authors.forename: Bence
authors.initials: B
authors.lastname: Laczó
authors.affiliation: Department of Clinical Neurophysiology, University Medical Center, Georg-August University, Göttingen, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Antal
authors.affiliation: Department of Psychiatry, Imland Clinic Rendsburg, Rendsburg, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Rothkegel
authors.affiliation: Department of Clinical Neurophysiology, University Medical Center, Georg-August University, Göttingen, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Paulus
mesh_terms: D000328:Adult; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D013997:Time Factors; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D055815:Young Adult
keywords: TMS; human; leg motor cortex; tDCS; tRNS