Paige G D, Telford L, Seidman S H, Barnes G R
Department of Neurology and the Center for Visual Science, University of Rochester, Rochester, New York 14642, USA.
J Neurophysiol. 1998 Nov;80(5):2391-404. doi: 10.1152/jn.1998.80.5.2391.
Human vestibuloocular reflex and its interactions with vision and fixation distance during linear and angular head movement. J. Neurophysiol. 80: 2391-2404, 1998. The vestibuloocular reflex (VOR) maintains visual image stability by generating eye movements that compensate for both angular (AVOR) and linear (LVOR) head movements, typically in concert with visual following mechanisms. The VORs are generally modulated by the "context" in which head movements are made. Three contextual influences on VOR performance were studied during passive head translations and rotations over a range of frequencies (0.5-4 Hz) that emphasized shifting dynamics in the VORs and visual following, primarily smooth pursuit. First, the dynamic characteristics of head movements themselves ("stimulus context") influence the VORs. Both the AVOR and LVOR operate with high-pass characteristics relative to a head velocity input, although the cutoff frequency of the AVOR (<0.1 Hz) is far below that of the LVOR ( approximately 1 Hz), and both perform well at high frequencies that exceed, but complement, the capabilities of smooth pursuit. Second, the LVOR and AVOR are modulated by fixation distance, implemented with a signal related to binocular vergence angle ("fixation context"). The effect was quantified by analyzing the response during each trial as a linear relationship between LVOR sensitivity (in deg/cm), or AVOR gain, and vergence (in m-1) to yield a slope (vergence influence) and an intercept (response at 0 vergence). Fixation distance (vergence) was modulated by presenting targets at different distances. The response slope rises with increasing frequency, but much more so for the LVOR than the AVOR, and reflects a positive relationship for all but the lowest stimulus frequencies in the AVOR. A third influence is the context of real and imagined targets on the VORs ("visual context"). This was studied in two ways-when targets were either earth-fixed to allow visual enhancement of the VOR or head-fixed to permit visual suppression. The VORs were assessed by extinguishing targets for brief periods while subjects continued to "fixate" them in darkness. The influences of real and imagined targets were most robust at lower frequencies, declining as stimulus frequency increased. The effects were nearly gone at 4 Hz. These properties were equivalent for the LVOR and AVOR and imply that the influences of real and imagined targets on the VORs generally follow low-pass and pursuit-like dynamics. The influence of imagined targets accounts for roughly one-third of the influence of real targets on the VORs at 0.5 Hz.
人类前庭眼反射及其在直线和角向头部运动过程中与视觉及注视距离的相互作用。《神经生理学杂志》80: 2391 - 2404, 1998年。前庭眼反射（VOR）通过产生眼球运动来维持视觉图像的稳定性，以补偿角向（AVOR）和直线（LVOR）头部运动，通常与视觉跟踪机制协同作用。VOR通常受头部运动发生时的“背景”调节。在被动头部平移和旋转过程中，研究了在一系列频率（0.5 - 4Hz）下对VOR性能的三种背景影响，这些频率强调了VOR和视觉跟踪（主要是平稳跟踪）中的动态变化。首先，头部运动本身的动态特性（“刺激背景”）影响VOR。相对于头部速度输入，AVOR和LVOR均以高通特性运行，尽管AVOR的截止频率（<0.1Hz）远低于LVOR的截止频率（约1Hz），并且两者在超过平稳跟踪能力但与之互补的高频下都表现良好。其次，LVOR和AVOR受注视距离调节，通过与双眼聚散角相关的信号来实现（“注视背景”）。通过分析每次试验期间的响应，将LVOR敏感性（以度/厘米为单位）或AVOR增益与聚散（以米-1为单位）之间的线性关系进行量化，以得出斜率（聚散影响）和截距（聚散为0时的响应）。通过在不同距离呈现目标来调节注视距离（聚散）。响应斜率随频率增加而上升，但LVOR比AVOR上升得更多，并且反映了除AVOR中最低刺激频率外所有频率下的正相关关系。第三种影响是真实和想象目标的背景对VOR的影响（“视觉背景”）。这通过两种方式进行研究——当目标要么固定于地面以允许视觉增强VOR，要么固定于头部以允许视觉抑制。通过在受试者在黑暗中继续“注视”目标的同时短暂熄灭目标来评估VOR。真实和想象目标的影响在较低频率下最为显著，随着刺激频率增加而下降。在4Hz时这些影响几乎消失。这些特性对于LVOR和AVOR是等效的，这意味着真实和想象目标对VORs的影响通常遵循低通和类似跟踪的动态特性。在0.5Hz时，想象目标的影响约占真实目标对VOR影响的三分之一。
