Modulation of iTBS after-effects via concurrent directional TDCS: A proof a principle study

Publication date: Available online 23 March 2017
Source:Brain Stimulation
Author(s): Sara Tremblay, Ricci Hannah, Vishal Rawji, John C. Rothwell
BackgroundExperiments in animals have shown that electrical polarisation of neurons in the hippocampus can modulate the long-term effects of theta burst stimulation on synaptic strength.ObjectiveWe examined whether a similar phenomenon could also be observed in human motor cortex (M1) using transcranial direct current stimulation (TDCS) to polarise neurons during unidirectional intermittent theta burst stimulation (iTBS).MethodsTDCS was applied during posterior-anterior iTBS using three different conditions: posterior-anterior TDCS (anode 3.5cm posterior to M1, cathode 3.5 cm anterior to M1), anterior-posterior TDCS (cathode 3.5cm posterior to M1, anode 3.5 cm anterior to M1), and sham TDCS.ResultWe found that when the direction of TDCS (posterior-anterior) matched the direction of the electrical field induced by iTBS, excitability changes were increased by 12% in comparison with iTBS combined with sham TDCS. When the TDCS was reversed (anterior-posterior), the excitatory effect of iTBS was abolished.ConclusionOur findings suggest that excitatory after-effects of iTBS can be modulated by directionally-specific TDCS.



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