视觉预期和注意指向对姿势和动作肌肉预期和补偿姿势调节的影响

Effects of visual anticipation and focus of attention on the anticipatory and compensatory postural adjustments of the lumbar postural muscle and upper limb focal muscle

采用经典落球试验研究范式,同步观察视觉预期和注意指向对腰部姿势肌肉和上肢运动肌肉预期和补偿姿势调节的影响,探索视觉预期和注意指向影响姿势控制的早期心理生理机制。24名青年志愿者(10名男性,14名女性)参与完成本实验,分别在有、无视觉预期以及注意指向"托盘稳定"或者"重心稳定"的实验条件下观察外部姿势干扰对腰部姿势肌肉(L5~S1腰部多裂肌)和上肢动作肌肉(肱二头肌)预期姿势调节(anticipatory postural adjustments,APAs)和补偿姿势调节(compensatory postural adjustments,CPAs)相关时间和强度参数的影响。APAs和CPAs的时间和强度参数通过获取被检肌肉s EMG信号并参照相关检测规范进行。结果显示:(1)视觉预期对多裂肌的APAs启动时间,对肱二头肌的APAs启动时间、APAs强度和CPAs强度有显著影响;(2)注意指向对多裂肌的CPAs启动时间和肱二头肌APAs启动时间有显著影响;(3)视觉预期和注意指向对肱二头肌的APAs启动时间和APAs强度有交互作用。研究认为,突发外部姿势干扰条件下姿势肌肉和动作肌肉的姿势调节策略具有一定的差异,视觉预期和注意指向仅对姿势肌肉的时间参数有影响,对动作肌肉APAs和CPAs时间和强度参数都产生调节作用,表明在中枢神经系统的姿势控制中,人体姿势策略的调节是通过对姿势肌肉和动作肌肉的双重控制来完成的,视觉预期效应和心理指向效应反映在对不同功能肌肉前馈控制和反馈控制相应参数的调节。

Body posture can be controlled by the central nervous system（CNS） in three ways： the feed-forward control（FFC）, the feed-back control（FBC）, and the voluntary control（VC）. These neural control strategies not only enable rapid postural muscle responses but also stabilize the center of body gravity. While many studies indicated that visual anticipation（VA） and focus of attention（FOA） can affect the commands from the CNS, the effect of VA/FOA on posture control is not clear. The present study employed the classic ball hitting test（BHT） to simultaneously examine the effect of the VA/FOA-caused pre-activations in the lumbar postural muscle and upper motor muscle. 24 college students（10 males, 14 females） participated in the present study. The BHTs were conducted using a 2 by 2 within-subject design. That is, the participants either anticipated（with eyes open） or not anticipated（with eyes closed） the hitting ball, and they either focused on stabilizing the center of body mass（COM） or focused on the holding pan. A ball of 1.5 kg was used as a load to trigger a perturbation. To study the effects of external perturbation on APAs and CPAs, homemade ball-hitting platform and surface EMG equipment were used to study the response latency and response intensity of the target muscles. Electric activities from the lumbar multifidus muscle（LM） and from the biceps brachiimuscle（BB） were collected. The response latency, response intensity of the APAs and CPAs of the target muscles were used to evaluate the effects on the postural and focal muscles. The results showed（1） VA significantly affected the APAs＇ latency of the LM, and also affected the APAs＇ latency, APAs＇ AEMG, and CPAs＇ AEMG of the BB;（2） FOA significantly affected the CPAs＇ latency of the LM, and the APAs＇ latency of the BB;（3） Interactions between VA/FOA and APAs＇ latency and APAs＇ AEMG of BB were significant. These results showed that CNS may use different postural strategies to control postural and motor muscles. That is, VA and FOA may only affect temporal characteristics of the postural muscle, but they can affect both temporal and intensity parameters of the motor muscle. The CNS postural-control system is controlled by both the postural and motor muscles under external perturbation. These findings shed light on the mechanism of the CNS posture-control system.