van Donkelaar P, Lee R G, Gellman R S
Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, Alberta, Canada.
Exp Brain Res. 1992;91(1):151-61. doi: 10.1007/BF00230023.
We have evaluated the use of visual information about the movement of a target in two tasks--tracking and interceptions--involving multi-joint reaching movements with the arm. Target velocity was either varied in a pseudorandom order (random condition) or was kept constant (predictable condition) across trials. Response latency decreased as target velocity increased in each condition. A simple model that assumes that latency is the sum of two components--the time taken for target motion to be detected, and a fixed processing time--provides a good fit to the data. Results from a step-ramp experiment, in which the target stepped a small distance immediately preceding the onset of the ramp motion, were consistent with this model. The characteristics of the first 100 ms of the response depended on the amount of information about target motion available to the subject. In the tracking task with randomly varied target velocities, the initial changes in hand velocity were largely independent of target velocity. In contrast, when the velocity was predictable the initial hand velocity depended on target velocity. Analogously, the initial changes in the direction of hand motion in the interception task were independent of target velocity in the random condition, but depended on target velocity in the predictable condition. The time course for development of response dependence was estimated by controlling the amount of visual information about target velocity available to the subject before the onset of limb movement. The results suggest that when target velocity was random, hand movement started before visual motion processing was complete. The response was subsequently adjusted after target velocity was computed. Subjects displayed idiosyncratic strategies during the catch-up phase in the tracking task. The peak hand velocity depended on target velocity and was similar for all subjects. The time at which the peak occurred, in contrast, varied substantially among subjects. In the interception task the hand paths were straighter in the predictable than in the random condition. This appeared to be the result of making adjustments in movement direction in the former condition to correct for initially inappropriate responses.
我们评估了在涉及手臂多关节伸展运动的两项任务（跟踪和拦截）中，关于目标运动的视觉信息的使用情况。在各试验中，目标速度要么以伪随机顺序变化（随机条件），要么保持恒定（可预测条件）。在每种条件下，反应潜伏期均随目标速度的增加而缩短。一个简单的模型假定潜伏期是两个成分之和——检测目标运动所需的时间和固定的处理时间——该模型与数据拟合良好。在一个阶跃斜坡实验中，目标在斜坡运动开始前立即小步移动一段距离，实验结果与该模型一致。反应最初100毫秒的特征取决于受试者可获得的关于目标运动的信息量。在目标速度随机变化的跟踪任务中，手部速度的初始变化在很大程度上与目标速度无关。相反，当速度可预测时，手部初始速度取决于目标速度。类似地，在拦截任务中，手部运动方向的初始变化在随机条件下与目标速度无关，但在可预测条件下取决于目标速度。通过控制在肢体运动开始前受试者可获得的关于目标速度的视觉信息量，估计了反应依赖性发展的时间进程。结果表明，当目标速度随机时，手部运动在视觉运动处理完成之前就开始了。随后在计算出目标速度后对反应进行调整。在跟踪任务的追赶阶段，受试者表现出独特的策略。手部峰值速度取决于目标速度，且所有受试者的峰值速度相似。相比之下，峰值出现的时间在受试者之间有很大差异。在拦截任务中，可预测条件下的手部路径比随机条件下更直。这似乎是在前一种条件下对运动方向进行调整以纠正最初不适当反应的结果。
