Tanaka Hiroaki, Nakamura Junji, Siozaki Tomoyuki, Ueta Kozo, Morioka Shu, Shomoto Koji, Okada Yohei
Graduate School of Health Sciences, Kio University, 4-2-2 Umami-naka, Koryo-cho, Kitakatsuragigun, Nara, 635-0832, Japan.
Department of Rehabilitation, Baba Memorial Hospital, Osaka, Japan.
Exp Brain Res. 2021 Mar;239(3):997-1007. doi: 10.1007/s00221-021-06033-8. Epub 2021 Jan 21.
The human vestibulospinal tract has important roles in postural control, but it has been unknown whether vestibulospinal tract excitability is influenced by the body's postures. We investigated whether postures influence the vestibulospinal tract excitability by a neurophysiological method, i.e., applying galvanic vestibular stimulation (GVS) 100 ms before tibial nerve stimulation evoking the soleus H-reflex. GVS is a percutaneous stimulation, and it has not been clarified how the cutaneous input from GVS influences the facilitation effect of cathodal GVS on the soleus H-reflex amplitude. In Experiment 1, we evaluated the effects of GVS on the soleus H-reflex amplitude of subjects in the prone, supine, and sitting positions in random order to clarify the differences in the GVS effects among these postures. In Experiment 2, to determine whether the effects of GVS in the supine and sitting positions are due solely to cutaneous input from GVS, we provided GVS and cutaneous stimulations as conditioning stimuli and compared the effects in both postures. Interaction effects between postures and stimulus conditions were observed in both experiments. The facilitation rate of the maximum H-reflex amplitude by GVS in the sitting position was significantly higher than those in the prone and supine positions (Experiment 1). The facilitation rate of GVS was significantly larger than the cutaneous stimulation only in the sitting position (Experiment 2). These results indicate that vestibulospinal tract excitability may be higher in the sitting position than in either lying position (prone and supine), due mainly to the increased need for postural control.
人类前庭脊髓束在姿势控制中发挥着重要作用，但尚不清楚前庭脊髓束的兴奋性是否受身体姿势的影响。我们采用神经生理学方法，即在刺激胫神经诱发比目鱼肌H反射前100毫秒施加电刺激前庭刺激（GVS），来研究姿势是否会影响前庭脊髓束的兴奋性。GVS是一种经皮刺激，目前尚不清楚GVS的皮肤传入如何影响阴极GVS对比目鱼肌H反射幅度的易化作用。在实验1中，我们以随机顺序评估了GVS对俯卧位、仰卧位和坐位受试者比目鱼肌H反射幅度的影响，以明确这些姿势之间GVS效应的差异。在实验2中，为了确定仰卧位和坐位时GVS的效应是否仅归因于GVS的皮肤传入，我们将GVS和皮肤刺激作为条件刺激，并比较了两种姿势下的效应。在两个实验中均观察到姿势与刺激条件之间的交互作用。坐位时GVS诱发的最大H反射幅度的易化率显著高于俯卧位和仰卧位（实验1）。仅在坐位时，GVS的易化率显著大于皮肤刺激（实验2）。这些结果表明，由于姿势控制需求增加，坐位时前庭脊髓束的兴奋性可能高于仰卧位和俯卧位。
