P 180. Bilateral sequential motor cortex stimulation improves skilled task learning

Abstract

Objective Increase of excitability and activation of the primary motor cortex (M1) can be achieved either by direct M1 stimulation with an excitatory TMS protocol or by stimulation of contralateral M1 with an inhibitory TMS protocol. The aim of the study was to check whether bilateral sequential stimulation of the primary motor cortex (M1) with both types of protocols, excitatory one over target M1 and inhibitory one over contralateral M1, would be able to improve performance on a skilled task more than unilateral stimulations could do. Methods 40 right-handed healthy subjects (mean age 25.7 ± 2.4 y, 16 women) participated in the study. They were divided into 4 matched experimental groups (10 subject each) according to the intervention they had: (1) facilitatory, intermittent TBS (iTBS) protocol over target M1-the iTBSt group; (2) inhibitory, continuous TBS (cTBS) protocol over contralateral M1-the cTBSc group; (3) contralateral cTBS followed by iTBS over target M1-the cTBSc/iTBSt group, and 4) placebo, sham iTBS protocol-Placebo group. During iTBS protocol, short bursts of 50 Hz stimulation (3 pulses of 80% aMT) were applied at 5 Hz in 2 s trains every 10 s, for a total of 600 pulses. The cTBS protocol was the same except that bursts were applied continuously (600 pulses in total). The sham iTBS protocol was the same as the iTBS protocol, but a placebo coil was used. Learning was evaluated by comparing scores on Purdue peg-board (PPB) test (number of pegs positioned by hand contralateral to target M1), before (B) and immediately after (T0) experimental interventions. Results In all groups, the PPB test scores increased at T0 in comparison to B showing clear learning effect ( Fig. 1 ). However, ANOVA showed significant Group effect (F(3,36) = 4.53, p = 0.008) for relative increase in number of pegs positioned on PBB test at T0. Post-hoc t-tests showed as significantly different from placebo only increase following bilateral sequential cTBSc/iTBSt protocol. Conclusion Neither direct stimulation of the target M1 nor indirect stimulation through release from contralateral M1 inhibition (by inhibiting contralateral M1) were able to increase motor skill learning above the level seen with placebo. Only bilateral sequential stimulation consisting of inhibition of contralateral M1 followed by stimulation of target M1 was able to significantly improve learning of a skilled motor task in healthy subjects. The findings may have implications for use of TMS neuromodulatory methods in neurorehabilitation.