title: Transcranial direct current stimulation over the motor association cortex induces plastic changes in ipsilateral primary motor and somatosensory cortices.
abstract: OBJECTIVE
  This study was performed to elucidate whether transcranial direct current stimulation (tDCS) over the motor association cortex modifies the excitability of primary motor (M1) and somatosensory (S1) cortices via neuronal connectivity.
  
  
  METHODS
  Anodal, cathodal, and sham tDCS (1 mA) over the left motor association cortex was applied to 10 subjects for 15 min using electrodes of two sizes (9 and 18 cm(2)). Both motor evoked potentials (MEPs) and somatosensory evoked potentials (SEPs) were recorded before, immediately after, and 15 min after tDCS. Electrode positions were confirmed by overlaying them on MRI anatomical surface images of two individuals.
  
  
  RESULTS
  After applying anodal tDCS using the large electrode, amplitudes of MEP components significantly decreased, whereas those of early SEP components (N20 and P25) increase. Opposite effects were observed on MEPs and SEPs after cathodal tDCS. However, a small electrode did not significantly influence either MEPs or SEPs, irrespective of polarity. The small electrode covered mainly the dorsal premotor cortex (PMd) while the large electrode involved the supplementary motor area (SMA) in addition to PMd.
  
  
  CONCLUSIONS
  These results suggest that anodal tDCS over PMd together with SMA enhanced the inhibitory input to M1 and excitatory input to S1, and that cathodal tDCS might lead to an opposite effect.
  
  
  CONCLUSIONS
  The finding that only the large electrode modulated M1 and S1 implies that activation of PMd together with SMA by tDCS can induce plastic changes in primary sensorimotor areas.
authors.affiliation: Department of Occupational Therapy, Faculty of Rehabilitation, Niigata University of Health and Welfare, Kitaku, Niigata, Japan. kirimoto@nuhw.ac.jp
authors.forename: Hikari
authors.initials: H
authors.lastname: Kirimoto
authors.forename: Katsuya
authors.initials: K
authors.lastname: Ogata
authors.forename: Hideaki
authors.initials: H
authors.lastname: Onishi
authors.forename: Mineo
authors.initials: M
authors.lastname: Oyama
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Goto
authors.forename: Shozo
authors.initials: S
authors.lastname: Tobimatsu
mesh_terms: D004558:Electric Stimulation; D004566:Electrodes; D004569:Electroencephalography; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D013003:Somatosensory Cortex / Q000502:physiology*; D055815:Young Adult