Dakin Christopher J, Héroux Martin E, Luu Billy L, Inglis John Timothy, Blouin Jean-Sébastien
School of Kinesiology, University of British Columbia, Vancouver, Canada; Institute of Neurology, University College London, London, United Kingdom;
School of Kinesiology, University of British Columbia, Vancouver, Canada; Neuroscience Research Australia, Sydney, Australia;
J Neurophysiol. 2016 Mar;115(3):1289-97. doi: 10.1152/jn.00512.2015. Epub 2015 Dec 16.
The soleus (Sol) and medial gastrocnemius (mGas) muscles have different patterns of activity during standing balance and may have distinct functional roles. Using surface electromyography we previously observed larger responses to galvanic vestibular stimulation (GVS) in the mGas compared with the Sol muscle. However, it is unclear whether this difference is an artifact that reflects limitations associated with surface electromyography recordings or whether a compensatory balance response to a vestibular error signal activates the mGas to a greater extent than the Sol. In the present study, we compared the effect of GVS on the discharge behavior of 9 Sol and 21 mGas motor units from freely standing subjects. In both Sol and mGas motor units, vestibular stimulation induced biphasic responses in measures of discharge timing [11 ± 5.0 (mGas) and 5.6 ± 3.8 (Sol) counts relative to the sham (mean ± SD)], and frequency [0.86 ± 0.6 Hz (mGas), 0.34 ± 0.2 Hz (Sol) change relative to the sham]. Peak-to-trough response amplitudes were significantly larger in the mGas (62% in the probability-based measure and 160% in the frequency-based measure) compared with the Sol (multiple P < 0.05). Our results provide direct evidence that vestibular signals have a larger influence on the discharge activity of motor units in the mGas compared with the Sol. More tentatively, these results indicate the mGas plays a greater role in vestibular-driven balance corrections during standing balance.
比目鱼肌（Sol）和内侧腓肠肌（mGas）在站立平衡过程中具有不同的活动模式，可能具有不同的功能作用。我们之前使用表面肌电图观察到，与比目鱼肌相比，内侧腓肠肌对电刺激前庭刺激（GVS）的反应更大。然而，尚不清楚这种差异是反映表面肌电图记录相关局限性的假象，还是对前庭误差信号的代偿性平衡反应对比目鱼肌更能激活内侧腓肠肌。在本研究中，我们比较了GVS对自由站立受试者的9条比目鱼肌和21条内侧腓肠肌运动单位放电行为的影响。在比目鱼肌和内侧腓肠肌运动单位中，前庭刺激均在前庭刺激诱导的放电时间测量中引起双相反应[相对于假刺激，内侧腓肠肌为11±5.0（内侧腓肠肌）和5.6±3.8（比目鱼肌）计数（平均值±标准差）]，以及频率[相对于假刺激，内侧腓肠肌为0.86±0.6Hz（内侧腓肠肌），比目鱼肌为0.34±0.2Hz（比目鱼肌）变化]。与比目鱼肌相比，内侧腓肠肌的峰谷反应幅度显著更大（基于概率的测量中为62%，基于频率的测量中为160%）（多个P<0.05）。我们的结果提供了直接证据，表明前庭信号对比目鱼肌运动单位放电活动的影响大于比目鱼肌。更初步地说，这些结果表明内侧腓肠肌在站立平衡期间前庭驱动的平衡校正中发挥更大作用。
