T031 One solution for variability of the long term effect induced by NIBSs

Abstract

The interindividual variability of the synaptic plasticity (SP) in human brain induced by NIBSs is one of topics in this field. In this communication, I will show which factors explain this variability and how to exclude such factors in MEP experiments in humans. How stable QPS The significant responder rate of QPS5 and QPS50 were 80% and 63%, respectively. Their rate of non-significant responder was 17% and 37%, but the opposite responder rate was 3% and 0%. The comparisons between several parameters QPSs suggested that the monophasic TMS pulse to use and 30 minutes duration of the QPS procedure have critical roles for stable SP induction. Factors for variability Two groups of variability may affect SP. Biological variability: BDNF polymorphism, meta-plasticity, baseline condition and so on. They may play a small role because QPS was not affected by them, and we are not able to control these factors. Methodological variability: Which synapse is the target for SP induction? SP induction of one synapse is better to see a clear effect. The direction of induced current and TMS pulse for the intervention (mono or bi phasic pulses) markedly affect this factor. How stable SP is induced? PSP, STP, early LTP or late LTP? The duration of the intervention may affect this factor. In QPS, monophasic TMS may induce quite pure SP and 30 minutes duration may induce a considerably stable SP. MEP recording after the intervention: MEP size should be affected by the excitability of cortical synapse, axonal excitability of the corticospinal tract, spinal synapse, motoneurons, neuromuscular junction and muscle. We should record MEPs mainly reflecting the excitability of motor cortical synapse on which SP is induced. My proposal (one solution) To use monophasic TMS pulses in the intervention as long as 30 minutes. During monitoring MEPs, we should use small intensity stimulation inducing the currents in the same direction as those used in the plasticity induction procedure, and also MEPs should be recorded in an active target muscle ( Nakamura et al., in press ). Download : Download high-res image (528KB) Download : Download full-size image Download : Download high-res image (864KB) Download : Download full-size image