McSorley Eugene, Haggard Patrick, Walker Robin
Department of Psychology, Royal Holloway, University of London, TW20 0EX, Egham, Surrey, UK.
Exp Brain Res. 2004 Apr;155(3):320-33. doi: 10.1007/s00221-003-1729-5. Epub 2004 Jan 15.
The trajectories of saccadic eye movements can be modulated by the presence of a competing visual distractor. In the present study the trajectories of vertical saccades curved away from a single visual distractor presented in one visual field, but tended to be straight when two distractors were presented at mirror symmetric locations in both visual fields. The spatial nature of the mirror distractor effect was examined by presenting a second distractor at mirror and non-mirror locations. Saccade trajectories also tended to be straight with both mirror and non-mirror symmetrical distractors. The relationship between the distractor location and saccade curvature was examined in a third experiment by manipulating the distractor-to-target spatial separation. Although there was a tendency for greater curvature when the distractor was presented in the same hemifield as the target there was no clear relationship between curvature and distractor location. The results show that the distractor modulation of saccade trajectory is not highly spatially specific and that it can be balanced by a second bilateral distractor in the opposite visual field. The results are interpreted in terms of a model in which the initial saccade direction and curvature back towards the saccade goal are controlled by separate processes. Initial saccade direction is modulated by the inhibition of distractor locations within a 'motor map' specifying saccade direction. Curvature back towards the saccade goal may be attributed to a feedback system, with a separate representation of the visual target location, that enables an on-line correction of the saccade during mid-flight.
眼球扫视运动的轨迹会受到竞争性视觉干扰物的影响而发生调制。在本研究中，垂直扫视的轨迹会向远离一个视野中呈现的单个视觉干扰物的方向弯曲，但当在两个视野的镜像对称位置呈现两个干扰物时，轨迹往往趋于直线。通过在镜像和非镜像位置呈现第二个干扰物，研究了镜像干扰物效应的空间性质。对于镜像和非镜像对称干扰物，扫视轨迹也往往趋于直线。在第三个实验中，通过操纵干扰物与目标的空间距离，研究了干扰物位置与扫视曲率之间的关系。尽管当干扰物与目标在同一半视野中呈现时，有曲率增大的趋势，但曲率与干扰物位置之间没有明确的关系。结果表明，干扰物对扫视轨迹的调制在空间上并非高度特异，并且可以被对侧视野中的第二个双侧干扰物所平衡。这些结果是根据一个模型来解释的，在该模型中，初始扫视方向和朝向扫视目标的曲率由不同的过程控制。初始扫视方向通过抑制“运动地图”内指定扫视方向的干扰物位置来进行调制。朝向扫视目标的曲率可能归因于一个反馈系统，并单独表征视觉目标位置，该系统能够在扫视过程中进行在线校正。
