非侵襲的脳刺激法のトピックス [in Japanese] Current Topics of Non-Invasive Brain Stimulation [in Japanese]
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Non-invasive brain stimulation (NIBS) has been developed and extensively studied for more than 30 years. NIBS can modulate cortical functions transcranially and induce focal effect on the cortex. Single-pulse TMS over the primary motor cortex (M1) can evoke motor evoked potentials (MEPs) which are used to estimate M1 excitability or pyramidal tract function. In addition, paired TMS can assess cortico-cortical connectivity, in which MEPs can be modulated by conditioning pulse over contralateral M1, frontal/parietal areas or even visual cortex. Single-pulse TMS also evokes cortical responses evaluated by TMS-EEGs, with which cortico-cortical interaction can be revealed with high temporal resolution. In contrast to single-pulse or paired-pulse TMS, repetitive transcranial magnetic stimulation (rTMS) and transcranial direct/alternating current stimulation (tDCS/tACS) can induce the lasting aftereffects. Enhancement or reduction of cortical excitability can be switched, depending on the parameters of NIBS. High frequency rTMS can enhance cortical excitability while low frequency one inhibit it. Patterned rTMS has been introduced recently. Repetitive paired pulse TMS (rPPS) uses paired pulses of 1.5 ms interstimulus interval delivered with suprathreshold intensity every 5 - 10 sec. rPPS can enhance cortical excitability with low stimulus rate (0.1-0.2 Hz). tDCS applies direct current to modulate cortical excitability, and would affect the cortical function through the modulation of membrane potentials. On the contrary, tACS uses alternating current which causes no DC shift, thus probably acts in a different way. tACS would entrain cortical oscillations, depending on its frequency and phase. Thus, it would be promising as a novel tool to explore brain functions. So far, NIBS has been utilized for basic research as well as clinical applications. The effect of intervention by NIBS is still controversial, because there are large inter-subject and intra-subject variability. Thus, further studies are necessary to develop more effective protocols.
- 福岡医学雑誌 = Fukuoka acta medica
福岡医学雑誌 = Fukuoka acta medica 108(7), 183-193, 2017-07-25