P 88. Unilateral and bilateral tDCS of the human motor cortex does not differentially modulate motor function in healthy adults

• Published in: Clinical neurophysiology 2013-10, Vol.124 (10), p.e107-e108
• Main Authors: Kidgell, D, Goodwill, A, Frazer, A, Daly, R
• Format: Article
• Language: English
• Subjects: Neurology
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2013.04.166

Introduction Transcranial direct current stimulation (tDCS) is a non-invasive technique that modulates the excitability of neurons within the primary motor cortex (M1). Neuronal excitability is modified by the application of direct currents in a polarity specific manner, with anodal-tDCS increasing excitability and cathodal decreasing excitability. Recently it has been shown that bilateral tDCS significantly modulates cortical excitability when compared to unilateral anodal stimulation. However, the effects of different tDCS montages on modulating motor performance are unclear. Further, it remains unclear if changes in motor performance following tDCS outlast the period of stimulation. Objective To determine whether unilateral or bilateral tDCS differentially modulates motor performance of the non-dominant hand in healthy participants. A secondary objective was to further elucidate the mechanisms underlying any potential aftereffects on motor performance following unilateral and bilateral tDCS. Methods Using a randomized, counter-balanced, cross-over design, with a one-week wash-out period, 9 participants (5 female and 4 male, age range 22–45 years) were exposed to 13 min of sham, unilateral or bilateral tDCS applied at 1.0 mA. In all tDCS conditions, the anode was placed over the “hot spot” of the non-dominant extensor carpi radialis longus muscle (ECRL) as determined by transcranial magnetic stimulation (TMS). The applied current was induced by a saline-soaked pair of surface sponge electrodes (25 cm2 ) delivered by a NeuroConn DC stimulator. TMS was used to measure M1 excitability and short-interval intracortical inhibition (SICI) of the non-dominant contralateral ECRL at baseline, immediately post, 30 and at 60 min following cessation of tDCS. We evaluated motor function at each of these time points in all conditions by having participants complete a Purdue peg board test. Results Both unilateral and bilateral tDCS facilitated motor performance immediately following tDCS (7 & 4% respectively), 30 min (13 & 6%) and 60 min post (21 & 9%)(all p < 0.05), but there were no differences between these two tDCS montages on modulating motor performance. In addition, both unilateral and bilateral tDCS increased cortical excitability immediately post stimulation (42 & 45% respectively) and it remained elevated for 30 min (57 & 72%, p < 0.05). Interestingly, the aftereffects of bilateral tDCS at 60 min on MEP amplitude remained elevated (70%) when compared to sham