S15-1. Plastic changes induced with NIBS

Abstract

We have several plasticity induction methods in human brain using repetitive transcranial magnetic stimulation (rTMS). I summarize the physiological basis of plasticity and physiological aspects of these methods. Regularly given rTMS was first reported to induce long-lasting effects, and low frequency rTMS (less than 1 Hz) induced LTD and high frequency (more than 5 Hz) rTMS induced LTP, whose frequency dependency is compatible with synaptic plasticity induction. Patterned rTMS, such as theta burst stimulation (TBS) or quadripulse stimulation (QPS), has been shown to induce similar effects and they have some superior points to the conventional rTMS. The paired associative stimulation which uses peripheral nerve stimulation and TMS together must induce spike timing dependent hetero-synaptic plasticity in contrast with the homosynaptic plasticity induced by the above described other methods. We have shown that the above modulation is produced by glutamate synaptic plasticity using the following examinations. The threshold of MEP to TMS indicating the axonal excitability of corticospinal tracts, the short interval intracortical inhibition probably indicating GABAA function, the long interval intracortical inhibition produced by GABAB interneurons, short interval intracortical facilitation reflecting glutamate EPSP summation or input-output curve of MEP indicating glutamate synaptic efficacy.