title: Modulating neuronal excitability in the motor cortex with tDCS shows moderate hemispheric asymmetry due to subjects' handedness: a pilot study.
abstract: OBJECTIVE
  Transcranial direct current stimulation (tDCS) has proven to be a useful tool for fundamental brain research as well as for attempts in therapy of neurological and psychiatric diseases by modulating neuronal plasticity. Little is understood about the effects of tDCS are influenced by hemispheric dominance, even less in terms of handedness. The aim of our pilot study was to investigate whether tDCS induced neuroplastic changes may be different in right- and left-handed individuals due to existing differences in hemispheric lateralisation.
  
  
  METHODS
  We measured changes in motor evoked potentials (MEPs) after application of tDCS in 8 right-handers, 8 left-handers and 8 mixed-handers according to the Edinburgh Handedness Inventory (EHI). In double-blind sessions, we applied either anodal or cathodal tDCS for 5 minutes for each hemisphere.
  
  
  RESULTS
  While motor thresholds (MT) seem to be not influenced by handedness significantly, in right-handed subjects we reproduced the well-known effects of tDCS: anodal stimulation increased while cathodal stimulation decreased MEP amplitudes. However, left-and mixed-handed subjects differed from right-handed subjects. After anodal stimulation of the left hemisphere the increase of the MEP amplitudes was stronger in right handed subjects than in left and mixed handed subjects. Interestingly, after cathodal stimulation of the left hemisphere this difference was less marked. The stimulation of the right hemisphere showed the same tendency, but results were not significant.
  
  
  CONCLUSIONS
  For the first time, we are able to demonstrate that the modulating effects of tDCS on corticospinal excitability differ moderately in the left-and mixed-handed population compared to right-handed subjects. The shown differences according to handedness should be taken into account in further studies.
authors.affiliation: Department of Clinical Neurophysiology, Georg-August University, Göttingen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schade
authors.forename: Vera
authors.initials: V
authors.lastname: Moliadze
authors.forename: Walter
authors.initials: W
authors.lastname: Paulus
authors.forename: Andrea
authors.initials: A
authors.lastname: Antal
mesh_terms: D000328:Adult; D004311:Double-Blind Method; D004599:Electric Stimulation Therapy / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000166:cytology / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D010865:Pilot Projects; D055815:Young Adult