Differential effects of facilitatory and inhibitory theta burst stimulation of the primary motor cortex on motor learning.

OBJECTIVE: To evaluate the differential effects on motor learning of two types of theta burst stimulation (TBS), the excitatory intermittent TBS (iTBS) and inhibitory continuous TBS (cTBS), if TBS is applied in an early stage of learning process. METHODS: Thirty right handed healthy people were randomly allocated into one of the three groups according to the intervention applied, iTBS, cTBS or placebo. The interventions and measurements targeted the non-dominant side. The reaction time task (RTT) and Purdue pegboard task (PPT) were used. Measurements and motor tasks were carried out at baseline (T0), immediately after the intervention (T1), and 30 min later (T2). RESULTS: Compared to placebo, following cTBS M1 excitability went down and PPT learning was slowed. Following iTBS M1 excitability increased temporarily and PPT learning pattern changed, but learning was not improved. The MEP and PPT changes induced during the T0-T1 time interval correlated significantly. CONCLUSIONS: The early consolidation of the learned material was much more influenced by the TBS induced promotion/suppression of the M1 functional plasticity reserves than by the absolute level of the M1 activation. SIGNIFICANCE: The results may help to better define the use of TBS in promotion of motor learning in neurorehabilitation and cognitive enhancement.