Tian Dongting, Izumi Shin-Ichi
Department of Physical Medicine and Rehabilitation, Tohoku University Graduates School of Medicine, Sendai, Japan.
Graduate School of Biomedical Engineering, Tohoku University, Sendai, Japan.
Front Neurosci. 2022 Apr 12;16:866245. doi: 10.3389/fnins.2022.866245. eCollection 2022.
Understanding the operation of cortical circuits is an important and necessary task in both neuroscience and neurorehabilitation. The functioning of the neocortex results from integrative neuronal activity, which can be probed non-invasively by transcranial magnetic stimulation (TMS). Despite a clear indication of the direct involvement of cortical neurons in TMS, no explicit connection model has been made between the microscopic neuronal landscape and the macroscopic TMS outcome. Here we have performed an integrative review of multidisciplinary evidence regarding motor cortex neurocytology and TMS-related neurophysiology with the aim of elucidating the micro-macro connections underlying TMS. Neurocytological evidence from animal and human studies has been reviewed to describe the landscape of the cortical neurons covering the taxonomy, morphology, circuit wiring, and excitatory-inhibitory balance. Evidence from TMS studies in healthy humans is discussed, with emphasis on the TMS pulse and paradigm selectivity that reflect the underlying neural circuitry constitution. As a result, we propose a preliminary neuronal model of the human motor cortex and then link the TMS mechanisms with the neuronal model by stimulus intensity, direction of induced current, and paired-pulse timing. As TMS bears great developmental potential for both a probe and modulator of neural network activity and neurotransmission, the connection model will act as a foundation for future combined studies of neurocytology and neurophysiology, as well as the technical advances and application of TMS.
理解皮质回路的运作在神经科学和神经康复领域都是一项重要且必要的任务。新皮质的功能源于整合性神经元活动，经颅磁刺激（TMS）可对其进行非侵入性探测。尽管已有明确迹象表明皮质神经元直接参与TMS，但在微观神经元格局与宏观TMS结果之间尚未建立明确的联系模型。在此，我们对有关运动皮质神经细胞学和TMS相关神经生理学的多学科证据进行了综合综述，旨在阐明TMS背后的微观-宏观联系。我们回顾了来自动物和人类研究的神经细胞学证据，以描述覆盖分类学、形态学、回路布线以及兴奋-抑制平衡的皮质神经元格局。我们讨论了来自健康人类TMS研究的证据，重点关注反映潜在神经回路构成的TMS脉冲和范式选择性。结果，我们提出了一个人类运动皮质的初步神经元模型，然后通过刺激强度、感应电流方向和双脉冲定时将TMS机制与该神经元模型联系起来。由于TMS作为神经网络活动和神经传递的探测工具及调制器具有巨大的发展潜力，该联系模型将为未来神经细胞学和神经生理学的联合研究以及TMS的技术进步和应用奠定基础。
