title: Modulation of iTBS after-effects via concurrent directional TDCS: A proof of principle study.
abstract: Polarising currents can modulate membrane potentials in animals, affecting the after-effect of theta burst stimulation (TBS) on synaptic strength.
  
  
  
  We examined whether a similar phenomenon could also be observed in human motor cortex (M1) using transcranial direct current stimulation (TDCS) during monophasic intermittent TBS (iTBS).
  
  
  
  TDCS was applied during posterior-anterior iTBS using three different conditions: posterior-anterior TDCS (anode 3.5 cm posterior to M1, cathode 3.5 cm anterior to M1), anterior-posterior TDCS (cathode 3.5 cm posterior to M1, anode 3.5 cm anterior to M1), and sham TDCS.
  
  
  
  When the direction of TDCS (posterior-anterior) matched the direction of the electrical field induced by iTBS, we found a 19% non-significant increase in excitability changes in comparison with iTBS combined with sham TDCS. When the TDCS was reversed (anterior-posterior), the excitatory effect of iTBS was abolished.
  
  
  
  Our findings suggest that excitatory after-effects of iTBS can be modulated by directionally-specific TDCS.
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, UK. Electronic address: s.tremblay@ucl.ac.uk.
authors.forename: Sara
authors.initials: S
authors.lastname: Tremblay
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, UK.
authors.forename: Ricci
authors.initials: R
authors.lastname: Hannah
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, UK.
authors.forename: Vishal
authors.initials: V
authors.lastname: Rawji
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, UK.
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
mesh_terms: D000328:Adult; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D000075082:Proof of Concept Study; D013826:Theta Rhythm; D065908:Transcranial Direct Current Stimulation / Q000009:adverse effects / Q000379:methods*
keywords: Intermittent theta burst stimulation; Primary motor cortex; Transcranial direct current stimulation; Transcranial magnetic stimulation