Tanaka M, Lisberger S G
Howard Hughes Medical Institute, Department of Physiology and W. M. Keck Foundation Center for Integrative Neuroscience, University of California, San Francisco, California 94143, USA.
J Neurophysiol. 2000 Oct;84(4):1748-62. doi: 10.1152/jn.2000.84.4.1748.
The appearance of a stationary but irrelevant cue triggers a smooth eye movement away from the position of the cue in monkeys that have been trained extensively to smoothly track the motion of moving targets while not making saccades to the stationary cue. We have analyzed the parameters that regulate the size of the cue-evoked smooth eye movement and examined whether presentation of the cue changes the initiation of pursuit for subsequent steps of target velocity. Cues evoked smooth eye movements in blocks of target motions that required smooth pursuit to moving targets, but evoked much smaller smooth eye movements in blocks that required saccades to stationary targets. The direction of the cue-evoked eye movement was always opposite to the position of the cue and did not depend on whether subsequent target motion was toward or away from the position of fixation. The latency of the cue-evoked smooth eye movement was near 100 ms and was slightly longer than the latency of pursuit for target motion away from the position of fixation. The size of the cue-evoked smooth eye movement was as large as 10 degrees /s and decreased as functions of the eccentricity of the cue and the illumination of the experimental room. To study the initiation of pursuit in the wake of the cues, we used bilateral cues at equal eccentricities to the right and left of the position of fixation. These evoked smaller eye velocities that were consistent with vector averaging of the responses to each cue. In the wake of bilateral cues, the initiation of pursuit was enhanced for target motion away from the position of fixation, but not for target motion toward the position of fixation. We suggest that the cue-evoked smooth eye movement is related to a previously postulated on-line gain control for pursuit, and that it is a side-effect of sudden activation of the gain-controlling element.
在经过广泛训练以平稳跟踪移动目标的运动而不向静止线索进行扫视的猴子中，一个静止但不相关的线索的出现会引发眼睛从线索位置平滑地移开。我们分析了调节线索诱发的平滑眼动大小的参数，并研究了线索的呈现是否会改变对后续目标速度步骤的追踪启动。线索在需要对移动目标进行平滑追踪的目标运动块中诱发了平滑眼动，但在需要对静止目标进行扫视的块中诱发的平滑眼动要小得多。线索诱发的眼动方向总是与线索的位置相反，并且不取决于后续目标运动是朝向还是远离注视位置。线索诱发的平滑眼动潜伏期接近100毫秒，略长于对远离注视位置的目标运动的追踪潜伏期。线索诱发的平滑眼动大小高达10度/秒，并随着线索的离心率和实验室照明的变化而减小。为了研究线索出现后追踪的启动情况，我们在注视位置的左右两侧使用了等离心率的双侧线索。这些诱发了较小的眼速度，这与对每个线索反应的矢量平均一致。在双侧线索出现后，对于远离注视位置的目标运动，追踪的启动得到增强，但对于朝向注视位置的目标运动则没有增强。我们认为，线索诱发的平滑眼动与先前假设的追踪在线增益控制有关，并且它是增益控制元件突然激活的副作用。
