Caudron Sébastien, Boy Fréderic, Forestier Nicolas, Guerraz Michel
Laboratoire de Psychologie et Neurocognition CNRS UMR 5105, Université de Savoie, 73376, Le Bourget du lac, France.
Exp Brain Res. 2008 Jan;184(1):53-9. doi: 10.1007/s00221-007-1079-9. Epub 2007 Aug 17.
Recent experiments have shown that the vestibular channel of balance control differs fundamentally from the visual channel. Whereas the response to a visual perturbation can be suppressed if the subject has awareness that an upcoming disturbance is likely to be caused by an external agent rather than by self-motion, a similar assumption cannot be made concerning the vestibular system. The present experiment investigated whether postural responses evoked by a proprioceptive perturbation (vibration of the Achilles' tendon at 90 Hz for 2.2 s) are either automatic and immune to expectation (similarly to vestibular responses) or cognitively penetrable (similarly to visual responses). Subjects (n = 12) stood on a force platform while stimuli were delivered either by the subject himself (self-triggered condition) or by the experimenter. For the latter condition, the stimulus was delivered either without warning (unpredictable condition) or at a fixed interval (500 ms) following an auditory cue (precue condition). Results showed that the backward CoP displacement induced by vibration was delayed by approximately 500 ms in the expected and self-triggered conditions compared to the unexpected condition. However, once initiated, the velocity of the backward displacement was higher in the self-triggered condition as compared to the unexpected condition. After a period of 2.2 s of vibration, the amplitude of this backward CoP displacement was similar in the three experimental conditions. Therefore, although expectation appears to delay the upcoming of the main backward body sway, it does not appear to be able to weight the impact of the proprioceptive stimulation. This suggested that afferents provided by the different sensory channels involved in postural control are not similarly susceptible to high level processes such as expectation.
最近的实验表明，平衡控制的前庭通道与视觉通道在根本上有所不同。如果受试者意识到即将到来的干扰可能是由外部因素而非自身运动引起的，那么对视觉干扰的反应就可以被抑制，但对于前庭系统则不能做出类似的假设。本实验研究了由本体感觉干扰（以90赫兹振动跟腱2.2秒）引发的姿势反应是自动的且不受预期影响（类似于前庭反应）还是可认知穿透的（类似于视觉反应）。12名受试者站在一个测力平台上，刺激要么由受试者自己施加（自触发条件），要么由实验者施加。对于后一种情况，刺激要么在没有警告的情况下施加（不可预测条件），要么在听觉提示（预提示条件）后的固定间隔（500毫秒）施加。结果表明，与意外条件相比，在预期和自触发条件下，由振动引起的向后的重心（CoP）位移延迟了约500毫秒。然而，一旦开始，自触发条件下向后位移的速度比意外条件下更高。在振动2.2秒后，这种向后的CoP位移幅度在三种实验条件下相似。因此，尽管预期似乎会延迟主要的向后身体摆动的到来，但它似乎无法权衡本体感觉刺激的影响。这表明参与姿势控制的不同感觉通道提供的传入信息对诸如预期等高级过程的敏感程度不同。
