Telford L, Seidman S H, Paige G D
Department of Neurology and Center for Visual Science, University of Rochester, Rochester, New York 14642, USA.
J Neurophysiol. 1997 Oct;78(4):1775-90. doi: 10.1152/jn.1997.78.4.1775.
Horizontal, vertical, and torsional eye movements were recorded using the magnetic search-coil technique during linear accelerations along the interaural (IA) and dorsoventral (DV) head axes. Four squirrel monkeys were translated sinusoidally over a range of frequencies (0.5-4.0 Hz) and amplitudes (0.1-0.7 g peak acceleration). The linear vestibuloocular reflex (LVOR) was recorded in darkness after brief presentations of visual targets at various distances from the subject. With subjects positioned upright or nose-up relative to gravity, IA translations generated conjugate horizontal (IA horizontal) eye movements, whereas DV translations with the head nose-up or right-side down generated conjugate vertical (DV vertical) responses. Both were compensatory for linear head motion and are thus translational LVOR responses. In concert with geometric requirements, both IA-horizontal and DV-vertical response sensitivities (in deg eye rotation/cm head translation) were related linearly to reciprocal fixation distance as measured by vergence (in m-1, or meter-angles, MA). The relationship was characterized by linear regressions, yielding sensitivity slopes (in deg.cm-1.MA-1) and intercepts (sensitivity at 0 vergence). Sensitivity slopes were greatest at 4.0 Hz, but were only slightly more than half the ideal required to maintain fixation. Slopes declined with decreasing frequency, becoming negligible at 0.5 Hz. Small responses were observed when vergence was zero (intercept), although no response is required. Like sensitivity slope, the intercept was largest at 4.0 Hz and declined with decreasing frequency. Phase lead was near zero (compensatory) at 4.0 Hz, but increased as frequency declined. Changes in head orientation, motion axis (IA vs. DV), and acceleration amplitude produced slight and sporadic changes in LVOR parameters. Translational LVOR response characteristics are consistent with high-pass filtering within LVOR pathways. Along with horizontal eye movements, IA translation generated small torsional responses. In contrast to the translational LVORs, IA-torsional responses were not systematically modulated by vergence angle. The IA-torsional LVOR is not compensatory for translation because it cannot maintain image stability. Rather, it likely compensates for the effective head tilt simulated by translation. When analyzed in terms of effective head tilt, torsional responses were greatest at the lowest frequency and declined as frequency increased, consistent with low-pass filtering of otolith input. It is unlikely that IA-torsional responses compensate for actual head tilt, however, because they were similar for both upright and nose-up head orientations. The IA-torsional and -horizontal LVORs seem to respond only to linear acceleration along the IA head axis, and the DV-vertical LVOR to acceleration along the head's DV axis, regardless of gravity.
在沿着双耳（IA）和背腹（DV）头轴的线性加速度过程中，使用磁搜索线圈技术记录水平、垂直和扭转眼球运动。四只松鼠猴在一系列频率（0.5 - 4.0 Hz）和振幅（0.1 - 0.7 g峰值加速度）范围内进行正弦平移。在向受试者呈现不同距离的视觉目标后，在黑暗中记录线性前庭眼反射（LVOR）。当受试者相对于重力直立或头朝上时，IA平移产生共轭水平（IA水平）眼球运动，而当头朝上或右侧朝下时的DV平移产生共轭垂直（DV垂直）反应。两者都是对头部线性运动的补偿，因此是平移LVOR反应。与几何要求一致，IA水平和DV垂直反应灵敏度（以度眼球旋转/厘米头部平移表示）与通过聚散度（以米 -1或米角，MA表示）测量的倒数注视距离呈线性相关。这种关系通过线性回归来表征，得出灵敏度斜率（以度·厘米 -1·MA -1表示）和截距（聚散度为0时的灵敏度）。灵敏度斜率在4.0 Hz时最大，但仅略高于维持注视所需理想值的一半。斜率随频率降低而下降，在0.5 Hz时变得可以忽略不计。当聚散度为零时（截距）观察到小的反应，尽管不需要反应。与灵敏度斜率一样，截距在4.0 Hz时最大，并随频率降低而下降。在4.0 Hz时相位超前接近零（补偿性），但随频率下降而增加。头部方向、运动轴（IA与DV）和加速度振幅的变化在LVOR参数中产生轻微且偶发的变化。平移LVOR反应特性与LVOR通路内的高通滤波一致。除了水平眼球运动外，IA平移还产生小的扭转反应。与平移LVOR不同，IA扭转反应不会因聚散角而受到系统调制。IA扭转LVOR不是对平移的补偿，因为它无法维持图像稳定性。相反，它可能是对平移模拟的有效头部倾斜进行补偿。当根据有效头部倾斜进行分析时，扭转反应在最低频率时最大，并随频率增加而下降，这与耳石输入的低通滤波一致。然而，IA扭转反应不太可能补偿实际头部倾斜，因为对于直立和头朝上的头部方向，它们是相似的。IA扭转和水平LVOR似乎仅对沿IA头轴的线性加速度做出反应，而DV垂直LVOR对沿头部DV轴的加速度做出反应，与重力无关。
