Demer J L
Jules Stein Eye Institute, University of California, Los Angeles 90024-7002.
J Vestib Res. 1994 Sep-Oct;4(5):355-70.
We investigated the effect of aging on vertical smooth pursuit, small-field optokinetic nystagmus (OKN), the vestibulo-ocular reflex (VOR), and visual-vestibular interactions (VVI). Telescopic spectacles were used to magnify the visual effects of head movements and accentuate the demand on VVI. Eleven normally sighted young subjects (age 30 +/- 6 y, mean +/- SD), and 9 normally sighted elderly subjects (age 70 +/- 8 y) were studied. Three types of stimulus motion were used: 1) predictable single sinusoidal frequencies from 0.8 to 3.2 Hz, 2) poorly predictable motion consisting of a sum of multiple harmonics of a 0.4 Hz fundamental, and 3) unpredictable velocity impulses. Tracking gains declined with frequency and stimulus unpredictability but were always greater for young than elderly subjects. Pursuit gain was always less than OKN gain for subjects tested under comparable conditions of frequency and velocity. In both subject groups, pursuit and OKN tracking exhibited phase lags at higher frequencies, particularly for poor predictable motion. Tracking phase lags were greater for pursuit than OKN and were consistently greater in the elderly than in young subjects. In young subjects, stimulus dimming using a 2 log neutral density filter reduced tracking gains and increased phase lags. In both young and elderly subjects, VOR gain was < 1.0 at low frequencies and increased slightly with increasing frequency. Visually enhanced VOR gain during normal vision was the ideal value of 1.0 at all frequencies in both subject groups. During wearing of telescopic spectacles, the young subjects exhibited marked gain enhancement that was greatest at lower frequencies and greater during predictable than unpredictable motion. Young subjects were able to suppress the VOR by fixation of real or imaginary targets moving with the head; this suppression was better at the lowest frequencies and for predictable motion. Phase errors were substantial for significant VVI in young subjects but were minimal in the elderly. Visual enhancement of VOR gain, as well as suppression by real and imaginary head-fixed targets, were attenuated in the elderly subjects. During rotations in which young subjects wore 4x telescopic spectacles, 2 log unit dimming of the visual environment reduced gain and increased phase lags. The deficiencies in VVI exhibited by elderly subjects are attributable both to deficits in the visual tracking component, as well as to nonvisual mechanisms, because even changes in mental set are less effective in modifying gain in older subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
我们研究了衰老对垂直平稳跟踪、小视野视动性眼震（OKN）、前庭眼反射（VOR）以及视觉-前庭相互作用（VVI）的影响。使用望远镜式眼镜放大头部运动的视觉效果，并增强对VVI的需求。研究了11名视力正常的年轻受试者（年龄30±6岁，均值±标准差）和9名视力正常的老年受试者（年龄70±8岁）。使用了三种类型的刺激运动：1）0.8至3.2赫兹的可预测单正弦频率；2）由0.4赫兹基频的多个谐波之和组成的难以预测的运动；3）不可预测的速度脉冲。跟踪增益随频率和刺激不可预测性而下降，但年轻受试者的增益始终高于老年受试者。在频率和速度相当的测试条件下，受试者的跟踪增益始终低于OKN增益。在两个受试者组中，跟踪和OKN跟踪在较高频率时均表现出相位滞后，尤其是对于难以预测的运动。跟踪相位滞后在跟踪中比OKN更大，并且在老年人中始终比年轻人更大。在年轻受试者中，使用2对数单位中性密度滤光片使刺激变暗会降低跟踪增益并增加相位滞后。在年轻和老年受试者中，VOR增益在低频时<1.0，并随频率增加而略有增加。在正常视觉期间，视觉增强的VOR增益在两个受试者组的所有频率下均为理想值1.0。在佩戴望远镜式眼镜期间，年轻受试者表现出明显的增益增强，在较低频率时最大，并且在可预测运动期间比不可预测运动时更大。年轻受试者能够通过注视随头部移动的真实或假想目标来抑制VOR；这种抑制在最低频率和可预测运动时更好。对于年轻受试者中显著的VVI，相位误差很大，但在老年人中最小。老年受试者中VOR增益的视觉增强以及真实和假想头部固定目标的抑制作用均减弱。在年轻受试者佩戴4倍望远镜式眼镜进行旋转期间，视觉环境2对数单位的变暗会降低增益并增加相位滞后。老年受试者表现出的VVI缺陷既归因于视觉跟踪成分的缺陷，也归因于非视觉机制，因为即使心理状态的改变在老年受试者中对增益的调节效果也较差。（摘要截断于250字）
