Kowler E, McKee S P
Department of Psychology, Rutgers University, New Brunswick, NJ 08903.
Vision Res. 1987;27(6):993-1015. doi: 10.1016/0042-6989(87)90014-9.
The precision of smooth pursuit eye movements was described by means of a new dependent measure, the "oculomotor difference threshold" (analogous to the perceptual difference threshold) which represents the smallest difference in target velocity that produces statistically distinguishable differences in eye velocity. Oculomotor difference thresholds for constant velocity motions were largest (greater than 50% of target velocity) during the initial 200 msec of target motion, despite fairly high average gains (0.7-1.4) during the same period. Oculomotor difference thresholds declined over time. By about 600-700 msec after the onset of target motion they reached values as low as the perceptual difference thresholds measured psychophysically with the same target velocities. The similarity of the difference thresholds suggests that equally precise sensory representations of target velocity influenced perception and smooth eye movements. Nonsensory influences on smooth eye movement were also found. Smooth pursuit velocity: (1) depended on the velocity of targets in preceding trials; (2) was decreased during the initial 200 msec of target motion when the duration of motion was reduced from 1 sec to 200 msec, a result which shows that high initial pursuit velocity depends on the expectation that pursuit will continue. These effects of context and expected duration allowed the eye to achieve quickly a velocity close to that of the target it was most likely to encounter. Study of the precision of pursuit may be valuable for characterizing its sensory input, but study of the effects of the context in which a stimulus appears and the effects of expectations about future target motion may be more valuable for understanding how smooth eye movements guarantee retinal image velocities optimal for vision.
通过一种新的因变量指标“动眼差异阈值”（类似于知觉差异阈值）来描述平稳跟踪眼球运动的精确性，该指标代表能在眼球速度上产生统计学上可区分差异的目标速度的最小差异。对于匀速运动，在目标运动的最初200毫秒内，动眼差异阈值最大（大于目标速度的50%），尽管在此期间平均增益相当高（0.7 - 1.4）。动眼差异阈值随时间下降。在目标运动开始后约600 - 700毫秒，它们达到与用相同目标速度进行心理物理学测量得到的知觉差异阈值一样低的值。差异阈值的相似性表明，对目标速度同样精确的感觉表征影响了知觉和平稳眼球运动。还发现了对平稳眼球运动的非感觉影响。平稳跟踪速度：（1）取决于先前试验中目标的速度；（2）当运动持续时间从1秒减少到200毫秒时，在目标运动的最初200毫秒内平稳跟踪速度会降低，这一结果表明较高的初始跟踪速度取决于跟踪将持续的预期。上下文和预期持续时间的这些影响使眼睛能够迅速达到接近其最可能遇到的目标的速度。对跟踪精确性的研究对于表征其感觉输入可能是有价值的，但对刺激出现的上下文的影响以及对未来目标运动的预期的影响的研究，对于理解平稳眼球运动如何保证视网膜图像速度对视觉而言是最佳的可能更有价值。
