Soechting John F, Mrotek Leigh A, Flanders Martha
Department of Neuroscience, University of Minnesota, 6-145 Jackson Hall, 321 Church St. SE, Minneapolis, MN 55455, USA.
Exp Brain Res. 2005 Jan;160(2):245-58. doi: 10.1007/s00221-004-2010-2. Epub 2004 Aug 18.
The directional control of smooth pursuit eye movements was studied by presenting human subjects with targets that moved in a straight line at a constant speed and then changed direction abruptly and unpredictably. To minimize the probability of saccadic responses in the interval following the target's change in direction, target position was offset so as to eliminate position error after the reaction time. Smooth pursuit speed declined at a latency of 90 ms, whereas the direction of smooth pursuit began to change later (130 ms). The amplitude of the offset in target position did not affect the subsequent smooth pursuit response. In other experiments, the target's speed or acceleration was changed abruptly at the time of the change in direction. Step changes in speed elicited short-latency responses in smooth pursuit tracking but step changes in acceleration did not. In all instances, the earliest component of the response did not depend on the parameters of the stimulus. The data were fit with a model in which smooth pursuit resulted from the vector addition of two components, one representing a response to the arrest of the initial target motion and the other the response to the onset of target motion in the new direction. This model gave an excellent fit but further analysis revealed nonlinear interactions between the two vector components. These interactions represented directional anisotropies both in terms of the initial tracking direction (which was either vertical or 45 degrees ) and in terms of the cardinal directions (vertical and horizontal).
通过向人类受试者呈现以恒定速度沿直线移动、然后突然且不可预测地改变方向的目标，研究了平稳跟踪眼球运动的方向控制。为了将目标方向改变后间隔内扫视反应的可能性降至最低，目标位置进行了偏移，以便在反应时间后消除位置误差。平稳跟踪速度在90毫秒的潜伏期下降，而平稳跟踪的方向稍后（130毫秒）开始改变。目标位置的偏移幅度不影响随后的平稳跟踪反应。在其他实验中，目标的速度或加速度在方向改变时突然改变。速度的阶跃变化在平稳跟踪中引发了短潜伏期反应，但加速度的阶跃变化则没有。在所有情况下，反应的最早成分不依赖于刺激参数。数据与一个模型拟合，在该模型中，平稳跟踪是由两个成分的矢量相加产生的，一个代表对初始目标运动停止的反应，另一个代表对新方向上目标运动开始的反应。该模型拟合得很好，但进一步分析揭示了两个矢量成分之间的非线性相互作用。这些相互作用在初始跟踪方向（垂直或45度）和基本方向（垂直和水平）方面都表现出方向各向异性。
