Ferrera V P, Lisberger S G
University of California at San Francisco, Department of Physiology, W.M. Keck Foundation Center for Integrative Neuroscience, USA.
Vis Neurosci. 1997 Mar-Apr;14(2):323-38. doi: 10.1017/s0952523800011457.
As a step toward understanding the mechanism by which targets are selected for smooth-pursuit eye movements, we examined the behavior of the pursuit system when monkeys were presented with two discrete moving visual targets. Two rhesus monkeys were trained to select a small moving target identified by its color in the presence of a moving distractor of another color. Smooth-pursuit eye movements were quantified in terms of the latency of the eye movement and the initial eye acceleration profile. We have previously shown that the latency of smooth pursuit, which is normally around 100 ms, can be extended to 150 ms or shortened to 85 ms depending on whether there is a distractor moving in the opposite or same direction, respectively, relative to the direction of the target. We have now measured this effect for a 360 deg range of distractor directions, and distractor speeds of 5-45 deg/s. We have also examined the effect of varying the spatial separation and temporal asynchrony between target and distractor. The results indicate that the effect of the distractor on the latency of pursuit depends on its direction of motion, and its spatial and temporal proximity to the target, but depends very little on the speed of the distractor. Furthermore, under the conditions of these experiments, the direction of the eye movement that is emitted in response to two competing moving stimuli is not a vectorial combination of the stimulus motions, but is solely determined by the direction of the target. The results are consistent with a competitive model for smooth-pursuit target selection and suggest that the competition takes place at a stage of the pursuit pathway that is between visual-motion processing and motor-response preparation.
作为朝着理解为平稳跟踪眼球运动选择目标的机制迈出的一步，我们研究了猴子面对两个离散移动视觉目标时跟踪系统的行为。训练了两只恒河猴，使其在存在另一种颜色的移动干扰物的情况下，选择一个通过颜色识别的小移动目标。根据眼球运动的潜伏期和初始眼球加速度曲线对平稳跟踪眼球运动进行了量化。我们之前已经表明，平稳跟踪的潜伏期通常约为100毫秒，根据干扰物相对于目标方向是沿相反方向还是相同方向移动，可分别延长至150毫秒或缩短至85毫秒。我们现在已经测量了干扰物方向在360度范围内以及干扰物速度在5 - 45度/秒时的这种效应。我们还研究了改变目标与干扰物之间的空间间隔和时间异步性的影响。结果表明，干扰物对跟踪潜伏期的影响取决于其运动方向以及它与目标的空间和时间接近程度，但几乎不取决于干扰物的速度。此外，在这些实验条件下，响应两个相互竞争的移动刺激而发出的眼球运动方向不是刺激运动的矢量组合，而是仅由目标方向决定。这些结果与平稳跟踪目标选择的竞争模型一致，并表明竞争发生在跟踪路径中视觉运动处理和运动反应准备之间的阶段。
