Waterston J A, Barnes G R
MRC Human Movement and Balance Unit, National Hospital for Neurology and Neurosurgery, London, UK.
J Vestib Res. 1992;2(1):71-88.
Recordings of head and eye movement were made during pursuit of mixed-frequency, pseudorandom target motion to study the mechanism of vestibulo-ocular reflex (VOR) suppression during head-free pursuit. When high velocity stimuli were used, slow-phase gaze velocity gains decreased significantly with increases in both absolute target velocity and the velocity ratio between the frequency components. These changes occurred independently of changes in the head displacement gain, which remained relatively constant at the lower frequency and were directly attributable to impaired suppression of the VOR. Similar effects were seen when visual feedback was degraded by tachistoscopic illumination of the target. The results indicate that visual feedback, rather than an efference copy of the head velocity signal, is essential for suppression of slow-phase vestibular eye movement during head-free pursuit. When head-free and head-fixed pursuit were compared, striking similarities were seen for both slow phase gaze velocity gain and phase, indicating that gaze control during smooth pursuit is largely independent of the degree of associated head movement. This suggests that the VOR is not switched off during head-free pursuit. An estimate of the underlying VOR gain was obtained by recording the vestibular response produced by active head movements in darkness. The rather higher estimates of VOR gain obtained using an imaginary earth-fixed target paradigm were found to predict head-free gains more closely than the gains obtained during imaginary pursuit of a moving target, suggesting that such measures may be more representative of the underlying VOR gain.
在追踪混合频率、伪随机目标运动过程中记录头部和眼球运动，以研究无头部追踪过程中前庭眼反射（VOR）抑制的机制。当使用高速刺激时，随着绝对目标速度以及频率成分之间速度比的增加，慢相注视速度增益显著降低。这些变化独立于头部位移增益的变化，头部位移增益在较低频率时保持相对恒定，且这些变化直接归因于VOR抑制受损。当通过速示器照亮目标使视觉反馈退化时，也观察到了类似的效果。结果表明，视觉反馈而非头部速度信号的传出副本，对于无头部追踪过程中慢相前庭眼球运动的抑制至关重要。当比较无头部和头部固定追踪时，在慢相注视速度增益和相位方面都观察到了惊人的相似性，这表明平稳追踪过程中的注视控制在很大程度上独立于相关头部运动的程度。这表明在无头部追踪过程中VOR并未关闭。通过记录在黑暗中主动头部运动产生的前庭反应，获得了潜在VOR增益的估计值。发现使用假想的固定于地球的目标范式获得的VOR增益估计值比在假想追踪移动目标过程中获得的增益更能紧密预测无头部增益，这表明此类测量可能更能代表潜在的VOR增益。
