Mohrmann H, Thier P
Sektion für Visuelle Sensomotorik, Neurologische Universitätsklinik, Tübingen, Germany.
Biol Cybern. 1995 Jun;73(1):83-93. doi: 10.1007/BF00199058.
Smooth-pursuit eye movements were recorded in two rhesus monkeys in order to compare the influence of structured visual backgrounds on smooth-pursuit initiation, steady-state pursuit and pursuit termination. Different target trajectories were used in order to study smooth-pursuit initiation and termination. The influence of visual backgrounds on pursuit initiation was characterized by recording ocular responses elicited by step-ramp target displacements starting from straight ahead. Pursuit termination was characterized by analysing the transition from steady-state smooth-pursuit to fixation when a centripetally directed target ramp was terminated by a small target step in the direction of the ramp as soon as the target had come close to the straightahead position. The quantification of steady-state pursuit was based on ocular responses elicited by either paradigm. In accordance with previous work, we found that the onset of smooth-pursuit eye movements was delayed and initial eye acceleration reduced in the presence of a structured visual background. Likewise, mean eye velocity during steady-state pursuit was reduced by structured visual backgrounds. However, neither the latency nor the time course of smooth-pursuit termination was altered when the homogeneous background was replaced by a structured visual background. The lack of sensitivity of pursuit termination to the presence of visual structured backgrounds supports a previous contention that pursuit termination is mediated by a process which is different from the ones mediating smooth-pursuit initiation and steady-state pursuit. The absence of any noticeable effect of structured backgrounds on pursuit termination suggests that at least the fast component of the optokinetic reflex is suppressed during pursuit termination.
为了比较结构化视觉背景对平稳跟踪启动、稳态跟踪和跟踪终止的影响，在两只恒河猴身上记录了平稳跟踪眼动。使用不同的目标轨迹来研究平稳跟踪启动和终止。通过记录从正前方开始的阶跃斜坡目标位移引发的眼部反应，来表征视觉背景对跟踪启动的影响。当向心方向的目标斜坡在目标接近正前方位置时，通过在斜坡方向上的小目标步长终止，分析从稳态平稳跟踪到注视的转变，以此表征跟踪终止。稳态跟踪的量化基于两种范式引发的眼部反应。与之前的研究一致，我们发现，在存在结构化视觉背景的情况下，平稳跟踪眼动的起始延迟，初始眼球加速度降低。同样，结构化视觉背景会降低稳态跟踪期间的平均眼球速度。然而，当均匀背景被结构化视觉背景取代时，平稳跟踪终止的潜伏期和时间进程均未改变。跟踪终止对视觉结构化背景的存在缺乏敏感性，这支持了之前的一种观点，即跟踪终止是由一个与介导平稳跟踪启动和稳态跟踪的过程不同的过程介导的。结构化背景对跟踪终止没有任何明显影响，这表明在跟踪终止期间，至少视动反射的快速成分受到了抑制。
