The modulation of cortical motor circuits and spinal reflexes using theta burst stimulation in healthy and dystonic...

Repetitive electrical stimulation has been applied to induce long-term changes in synaptic strength in animal preparations. It is generally believed that such changes in synapses form the basis of neural plasticity. Recently, several techniques, including repetitive transcranial magnetic stimulation (rTMS), have been developed to attempt to replicate similar plasticity effects in the brains of conscious humans. However, traditional paradigms of rTMS usually require lengthy stimulation and relatively high stimulus intensity. In light of these problems, a novel rTMS paradigm- theta burst stimulation (TBS) - was developed. TBS is able to produce plasticity-like effects more efficiently and powerfully than traditional protocols. The excitability of circuits within the motor cortex can be modified not only by TBS over the primary motor cortex but also when it is delivered to the premotor area. Moreover, TBS over the premotor cortex modifies aspects of spinal reflexes. Studies using TBS over the motor and premotor cortices provide further understanding of dystonia, and the results also distinguish the different mechanisms of the effects of TBS given to the primary motor and premotor cortices. In addition, some data also support the hypothesis that TBS is a potential candidate technique to help restore damaged motor functions through brain stimulation.