Knox Paul C, Bekkour Tarik
Division of Orthoptics, University of Liverpool, Thompson Yates Building, Brownlow Hill, L69 3BX, Liverpool, UK.
Exp Brain Res. 2004 Feb;154(4):494-503. doi: 10.1007/s00221-003-1686-z. Epub 2003 Nov 15.
In order to extract information from the visual world, it is necessary to bring the images of objects of interest to rest on the high acuity part of the retina, the fovea. Primates, including humans, use two types of eye movement, saccades and smooth pursuit, to accomplish this. While classically conceived of as being separate and distinct, various lines of evidence indicate a close linkage between these two eye movement systems. They are often investigated at a behavioural level by presenting subjects with single targets to saccade or to track. We investigated the effect of presenting a single stationary distractor at various positions in the visual field at the same time as a moving target which subjects were instructed to track. We found that while a stationary distractor presented in the contralateral visual field and part of the ipsilateral visual field increased pursuit latency in an eccentricity dependent manner, a distractor presented in the ipsilateral visual field, within 45 degrees of the axis along which the pursuit target moved, had no effect on latency. We found no evidence that within this region distractors modified eye velocity during the early part of the pursuit response. This spatial pattern of the effect of a stationary distractor on pursuit latency is very similar to the effect of distractors on saccade latency. Our results provide behavioural evidence supporting the hypothesis that the processes that determine when an eye movement is made are linked, but that those determining the form of that eye movement are substantially independent.
为了从视觉世界中提取信息，有必要将感兴趣物体的图像聚焦在视网膜的高敏锐度区域——中央凹上。包括人类在内的灵长类动物利用两种眼球运动，即扫视和平稳跟踪来实现这一点。虽然传统上认为这两种眼球运动系统是相互独立且截然不同的，但各种证据表明这两个系统之间存在紧密联系。它们通常在行为层面进行研究，方法是向受试者呈现单个目标以供其扫视或跟踪。我们研究了在受试者被要求跟踪一个移动目标的同时，在视野的不同位置呈现单个静止干扰物的影响。我们发现，虽然在对侧视野和部分同侧视野中呈现的静止干扰物会以与偏心度相关的方式增加跟踪潜伏期，但在同侧视野中，在跟踪目标移动轴的45度范围内呈现的干扰物对潜伏期没有影响。我们没有发现证据表明在该区域内干扰物会在跟踪反应的早期阶段改变眼球速度。静止干扰物对跟踪潜伏期的这种空间效应模式与干扰物对扫视潜伏期的效应非常相似。我们的结果提供了行为证据，支持这样一种假设，即决定何时进行眼球运动的过程是相关联的，但决定该眼球运动形式的过程在很大程度上是独立的。
