Effects of horizontal-vertical eye positions on the 3D on-direction of extraocular muscles and extraocular motoneurons.

1.对3只头部稳定的恒河猴(Macaca Fuscata)进行了实验研究。采用双巩膜搜索线圈方法进行三维眼动记录。滑车神经纤维用细胞外单单位记录进行鉴定。此后，在自发眼球运动过程中，每隔2秒刺激滑车交叉附近部位的滑车神经纤维，同时保持不同的静态翻滚姿势(直立、40ﾟ右耳向下和40ﾟ左耳向下)。刺激序列由0.25ms负矩形脉冲组成。刺激频率为500 Hz，电流强度为10-50 MUA，训练时间为25-200ms。在刺激期间，电刺激会将眼睛从Listing的飞机上移开。之后，在刺激结束后6-8ms开始向列表平面漂移，这与刺激开始和眼动开始之间的潜伏期相同。诱发眼球运动由大的扭转成分、大的向下成分和小的外展成分组成。诱发的方向与解剖学上报道的恒河猴上斜肌的拉动方向相似。诱发眼球运动的旋转轴与电刺激强度和持续时间无关。平均而言，诱发眼球运动在冠状(扭转-垂直)平面上的旋转轴与初始眼球位置的水平分量无关。我们的结论是，在清醒的猕猴中，电刺激滑车神经诱发的眼球旋转轴稳定在冠状平面上，几乎平行于上斜肌路径和眼球假想中心形成的平面。据报道，软滑轮在上、下、内侧和外直肌中不能有效地在上斜肌中工作。

1. Three head-stabilized monkeys (Macaca fuscata) were engaged in this study. A dual scleral search coil method was used for three-dimensional eye movement recordings. Trochlear nerve fibers were identified with extracellular single unit recordings. Thereafter, we stimulated the trochlear nerve fibers at the sites near to the trochlear decussation every 2 seconds during spontaneous eye movements while holding each monkey in different static roll positions (upright, 40ﾟ right ear down and 40ﾟ left ear down).2. Stimulation trains consisted of 0.25 ms negative rectangular pulses. Stimulus frequency was 500 Hz and current strength, and train duration were varied over the ranges of 10 -50 muA and 25-200msec.3. Electrical stimulation moved the eye away from Listing's plane during stimulation periods. Afterwards, drifts back to Listing's plane started 6-8 ms after stimulus end points, which was the same latency observed between stimulus onset and eye movement onset. Evoked eye movements were consisted of large intorsional and large downward components and small abduction components. The evoked direction was similar to the anatomically reported pulling direction of the superior oblique muscle in rhesus monkeys. The axis of rotation of evoked eye movements was independent of the electrical stimulation intensity and duration. On average, the axis of rotation of evoked eye movements in the coronal (torsional-vertical) plane was independent of the horizontal component of initial eye positions.4. We conclude that, in the alert monkeys, the axis of eye rotation evoked by electrical stimulation of the trochlear nerve is stabilized to the orbit in coronal plane which is almost in parallel with the plane formed by the superior oblique muscle path and the imaginary center of eye ball. Soft pulley that is reported in the superior, inferior, medial and lateral rectus muscles does not work effectively in the superior oblique muscle.