Abstract
Repetitive transcranial magnetic stimulation (rTMS) is a useful method to noninvasively induce excitability changes in the stimulated and its tightly related cortices. The long lasting excitability changes after rTMS are considered as their neuronal synaptic plasticity changes. Recently, the efficacy of rTMS has been studied for neurological disorders, such as Parkinson’s disease (PD). A double blind randomized trial for effectiveness of 5Hz rTMS over the supplementary motor by Parkinson’s Disease Study Group in Japan showed that the rTMS significantly improved UPDRS III. However, the appropriate stimulus parameters (stimulus frequency, intensity, location etc) of rTMS have not been established to induce clinical efficacy.
We recently reported a new rTMS method, quatri-pulse magnetic stimulation (QPS). Repeated trains of four monophasic TMS pulses separated by interstimulus intervals of 1.5-100ms were applied over the motor cortex. QPS at short inter-vals (1.5-10ms) potentiated motor evoked potentials (MEPs), whilst QPS at long intervals (30 -100ms) depressed them. QPS can produce bidirectional after-effects depending on the TMS pulse interval, which were compatible with the synaptic plasticity consistent with Bienenstock-Cooper-Munro (BCM) theory. This new rTMS has a possibility to pro-duce more powerful beneficial effects on neurological symptoms.
