Clendaniel R A, Lasker D M, Minor L B
Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-0910, USA.
J Neurophysiol. 2001 Oct;86(4):1594-611. doi: 10.1152/jn.2001.86.4.1594.
The horizontal angular vestibuloocular reflex (VOR) evoked by sinusoidal rotations from 0.5 to 15 Hz and acceleration steps up to 3,000 degrees /s(2) to 150 degrees /s was studied in six squirrel monkeys following adaptation with x2.2 magnifying and x0.45 minimizing spectacles. For sinusoidal rotations with peak velocities of 20 degrees /s, there were significant changes in gain at all frequencies; however, the greatest gain changes occurred at the lower frequencies. The frequency- and velocity-dependent gain enhancement seen in normal monkeys was accentuated following adaptation to magnifying spectacles and diminished with adaptation to minimizing spectacles. A differential increase in gain for the steps of acceleration was noted after adaptation to the magnifying spectacles. The gain during the acceleration portion, G(A), of a step of acceleration (3,000 degrees /s(2) to 150 degrees /s) increased from preadaptation values of 1.05 +/- 0.08 to 1.96 +/- 0.16, while the gain during the velocity plateau, G(V), only increased from 0.93 +/- 0.04 to 1.36 +/- 0.08. Polynomial fits to the trajectory of the response during the acceleration step revealed a greater increase in the cubic than the linear term following adaptation with the magnifying lenses. Following adaptation to the minimizing lenses, the value of G(A) decreased to 0.61 +/- 0.08, and the value of G(V) decreased to 0.59 +/- 0.09 for the 3,000 degrees /s(2) steps of acceleration. Polynomial fits to the trajectory of the response during the acceleration step revealed that there was a significantly greater reduction in the cubic term than in the linear term following adaptation with the minimizing lenses. These findings indicate that there is greater modification of the nonlinear as compared with the linear component of the VOR with spectacle-induced adaptation. In addition, the latency to the onset of the adapted response varied with the dynamics of the stimulus. The findings were modeled with a bilateral model of the VOR containing linear and nonlinear pathways that describe the normal behavior and adaptive processes. Adaptation for the linear pathway is described by a transfer function that shows the dependence of adaptation on the frequency of the head movement. The adaptive process for the nonlinear pathway is a gain enhancement element that provides for the accentuated gain with rising head velocity and the increased cubic component of the responses to steps of acceleration. While this model is substantially different from earlier models of VOR adaptation, it accounts for the data in the present experiments and also predicts the findings observed in the earlier studies.
在六只松鼠猴佩戴2.2倍放大眼镜和0.45倍缩小眼镜适应后，研究了0.5至15赫兹正弦旋转以及高达3000度/秒²至150度/秒的加速度阶跃所诱发的水平角前庭眼反射（VOR）。对于峰值速度为20度/秒的正弦旋转，所有频率下的增益均有显著变化；然而，最大的增益变化发生在较低频率。正常猴子中观察到的频率和速度依赖性增益增强在适应放大眼镜后更为明显，而在适应缩小眼镜后则减弱。适应放大眼镜后，加速度阶跃的增益有差异增加。加速度阶跃（3000度/秒²至150度/秒）的加速部分G(A)的增益从适应前的1.05±0.08增加到1.96±0.16，而速度平台期G(V)的增益仅从0.93±0.04增加到1.36±0.08。对加速度阶跃期间响应轨迹的多项式拟合显示，在使用放大镜片适应后，三次项的增加比线性项更大。适应缩小镜片后，对于3000度/秒²的加速度阶跃，G(A)的值降至0.61±0.08，G(V)的值降至0.59±0.09。对加速度阶跃期间响应轨迹的多项式拟合显示，在使用缩小镜片适应后，三次项的减少比线性项显著更大。这些发现表明，与VOR的线性成分相比，眼镜诱发的适应对非线性成分的改变更大。此外，适应反应开始的潜伏期随刺激的动力学而变化。这些发现用一个包含描述正常行为和适应过程的线性和非线性通路的VOR双侧模型进行了模拟。线性通路的适应由一个传递函数描述，该函数显示了适应对头部运动频率的依赖性。非线性通路的适应过程是一个增益增强元件，它随着头部速度的增加提供增强的增益以及对加速度阶跃响应的增加的三次项成分。虽然这个模型与早期的VOR适应模型有很大不同，但它解释了本实验中的数据，也预测了早期研究中观察到的结果。
