Forbes Patrick A, Siegmund Gunter P, Happee Riender, Schouten Alfred C, Blouin Jean-Sébastien
Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands;
School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada; MEA Forensic Engineers & Scientists, Richmond, British Columbia, Canada.
J Neurophysiol. 2014 Oct 1;112(7):1692-702. doi: 10.1152/jn.00343.2014. Epub 2014 Jul 9.
Percutaneous electrical vestibular stimulation evokes reflexive responses in appendicular muscles that are suppressed during tasks in which the muscles are not contributing to balance control. In neck muscles, which stabilize the head on the torso and in space, it is unclear whether similar postural task dependence shapes vestibular reflexes. We investigated whether vestibulocollic reflexes are modulated during tasks in which vestibular information is not directly relevant to maintaining the head balanced on the torso. We hypothesized that vestibulocollic reflexes would be 1) evoked when neck muscles are not involved in balancing the head on the torso and 2) invariant across synergistic neck muscle contraction tasks. Muscle activity was recorded bilaterally in sternocleidomastoid and splenius capitis muscles during head-free and head-fixed conditions while subjects were exposed to stochastic electrical vestibular stimulation (± 5 mA, 0-75 Hz). Significant vestibular reflex responses (P < 0.05) were observed during head-free and head-fixed trials. Response magnitude and timing were similar between head-free and head-fixed trials for sternocleidomastoid, but splenius capitis magnitudes decreased with the head fixed by ∼ 25% (P < 0.05). Nevertheless, this indicates that vestibulocollic responses are evoked independent of the requirement to maintain postural control of the head on the torso. Response magnitude and timing were similar across focal muscle contractions (i.e., axial rotation/flexion/extension) provided the muscle was active. In contrast, when subjects cocontracted neck muscles, vestibular-evoked responses decreased in sternocleidomastoid by ∼ 30-45% (P < 0.05) compared with focal muscle contractions but remained unchanged in splenius capitis. These results indicate robust vestibulocollic reflex coupling, which we suggest functions through its closed-loop influence on head posture to ensure cervical spine stabilization.
经皮电前庭刺激可诱发附属肌肉的反射性反应，这些反应在肌肉不参与平衡控制的任务中会受到抑制。在颈部肌肉中，其作用是稳定头部在躯干上及空间中的位置，目前尚不清楚类似的姿势任务依赖性是否会影响前庭反射。我们研究了在前庭信息与维持头部在躯干上的平衡无直接关联的任务中，前庭颈反射是否会受到调制。我们假设前庭颈反射会：1）在颈部肌肉不参与平衡头部在躯干上的位置时被诱发；2）在协同颈部肌肉收缩任务中保持不变。在无头部和头部固定的条件下，当受试者接受随机电前庭刺激（±5 mA，0 - 75 Hz）时，双侧记录胸锁乳突肌和头夹肌的肌肉活动。在无头部和头部固定试验中均观察到显著的前庭反射反应（P < 0.05）。胸锁乳突肌在无头部和头部固定试验中的反应幅度和时间相似，但头夹肌的幅度在头部固定时降低了约25%（P < 0.05）。尽管如此，这表明前庭颈反应的诱发与维持头部在躯干上的姿势控制需求无关。只要肌肉处于活动状态，在局部肌肉收缩（即轴向旋转/屈曲/伸展）过程中，反应幅度和时间相似。相比之下，当受试者协同收缩颈部肌肉时，与局部肌肉收缩相比，胸锁乳突肌的前庭诱发反应降低了约30 - 45%（P < 0.05），但头夹肌的反应保持不变。这些结果表明存在强大的前庭颈反射耦合，我们认为其通过对头部姿势的闭环影响来发挥作用，以确保颈椎稳定。
