Changing the brain with non-invasive stimulation

The human adult brain can change with experience, a phenomenon called neuroplasticity. Neuroplasticity is a particularly critical process for learning and memory. Not surprisingly, there is a lot of interest in developing techniques that can induce neuroplasticity to enhance learning and memory. In the brain region responsible for voluntary movement – the motor cortex – inducing neuroplasticity non‐invasively could, for example, help people to relearn movements after stroke. Repetitive transcranial magnetic stimulation (rTMS) is a non‐invasive and innovative brain stimulation technique, capable of temporarily inducing motor cortex neuroplasticity. However, responses to rTMS are highly variable between individuals – limiting the clinical potential of this technique. Recent evidence suggests that applying rTMS at a low intensity (rTMSLOW) can down‐regulate cortical inhibition, a process that underlies neuroplasticity. We investigated whether applying the inhibition‐reducing rTMSLOW protocol, prior to the conventional plasticity‐inducing rTMS protocol, could induce more reliable neuroplasticity responses. Thirty‐two healthy adults participated in two experimental sessions: 1) conventional rTMS primed by rTMSLOW; 2) conventional rTMS‐alone. The within‐subjects design ensured that inter‐individual variance in responses to the different stimulation protocols would not confound the results. To measure neuroplasticity, excitability of the motor cortex was measured before and after rTMS; a change in motor cortex excitability indicates rTMS‐induced neuroplasticity. Results showed that applying the rTMSLOW protocol, prior to conventional rTMS, produced longer‐lasting and more reliable changes in motor cortex excitability (compared to conventional rTMS‐alone). This finding provides preliminary evidence for a reliable approach to induce neuroplasticity in the motor cortex. This is an important first step for the development of rehabilitation interventions that may reliably improve voluntary movement in clinical populations (e.g., stroke survivors and Parkinson's disease patients)