Heskin-Sweezie Raquel, Farrow Karl, Broussard Dianne M
Toronto Western Research Institute, University Health Network, Canada.
Brain Res. 2007 Apr 27;1143:132-42. doi: 10.1016/j.brainres.2007.01.104. Epub 2007 Feb 1.
Adaptive rescaling is a widespread phenomenon that dynamically adjusts the input-output relationship of a sensory system in response to changes in the ambient stimulus conditions. Rescaling has been described in the central vestibular neurons of normal cats. After recovery from unilateral vestibular damage, the vestibulo-ocular reflex (VOR) remains nonlinear for rotation toward the damaged side. Therefore, rescaling in the VOR pathway may be especially important after damage. Here, we demonstrate that central vestibular neurons adjust their input-output relationships depending on the input velocity range, suggesting that adaptive rescaling is preserved after vestibular damage and can contribute to the performance of the VOR. We recorded from isolated vestibular neurons in alert cats that had recovered from unilateral vestibular damage. The peak velocity of 1-Hz sinusoidal rotation was varied from 10 to 120 degrees/s and the sensitivities and dynamic ranges of vestibular neurons were measured. Most neuronal responses showed significant nonlinearities even at the lowest peak velocity that we tested. Significant rescaling was seen in the responses of neurons both ipsilateral and contralateral to chronic unilateral damage. On the average, when the peak rotational velocity increased by a factor of 8, the average sensitivity to rotation decreased by roughly a factor of 2. Rescaling did not depend on eye movement signals. Our results suggest that the dynamic ranges of central neurons are extended by rescaling and that, after vestibular damage, adaptive rescaling may act to reduce nonlinearities in the response of the VOR to rotation at high speeds.
适应性重新缩放是一种普遍现象，它会根据周围刺激条件的变化动态调整感觉系统的输入-输出关系。重新缩放现象已在正常猫的中枢前庭神经元中得到描述。单侧前庭损伤恢复后，向损伤侧旋转时前庭眼反射（VOR）仍呈非线性。因此，VOR通路中的重新缩放可能在损伤后尤为重要。在此，我们证明中枢前庭神经元会根据输入速度范围调整其输入-输出关系，这表明前庭损伤后适应性重新缩放得以保留，并有助于VOR的表现。我们记录了从单侧前庭损伤恢复后的清醒猫的孤立前庭神经元的活动。1赫兹正弦旋转的峰值速度在10至120度/秒之间变化，并测量了前庭神经元的敏感性和动态范围。即使在我们测试的最低峰值速度下，大多数神经元反应也显示出明显的非线性。在慢性单侧损伤同侧和对侧的神经元反应中均观察到显著的重新缩放。平均而言，当峰值旋转速度增加8倍时，对旋转的平均敏感性大约降低2倍。重新缩放不依赖于眼动信号。我们的结果表明，中枢神经元的动态范围通过重新缩放得以扩展，并且在前庭损伤后，适应性重新缩放可能起到减少VOR对高速旋转反应中的非线性的作用。
