Lee D, Port N L, Georgopoulos A P
Brain Sciences Center (11B), Veterans Affairs Medical Center, Minneapolis, MN 55417, USA.
Exp Brain Res. 1997 Oct;116(3):421-33. doi: 10.1007/pl00005770.
We studied the kinematic characteristics of arm movements and their relation to a stimulus moving with a wide range of velocity and acceleration. The target traveled at constant acceleration, constant deceleration, or constant velocity for 0.5-2.0 s, until it arrived at a location where it was required to be intercepted. For fast moving targets, subjects produced single movements with symmetrical, bell-shaped velocity profiles. In contrast, for slowly moving targets, hand velocity profiles displayed multiple peaks, which suggests a control mechanism that produces a series of discrete submovements according to characteristics of target motion. To analyze how temporal and spatial aspects of these submovements are influenced by target motion, we decomposed the vertical hand velocity profiles into bell-shaped velocity pulses according to the minimum-jerk model. The number of submovements was roughly proportional to the movement time, resulting in a relatively constant submovement frequency (approximately 2.5 Hz). On the other hand, the submovement onset asynchrony showed significantly more variability than the intersubmovement interval, indicating that the submovement onset was delayed more following a submovement with a longer duration. Examination of submovement amplitude and its relation to target motion revealed that the subjects achieved interception mainly by producing a series of submovements that would keep the displacement of the hand proportional to the first-order estimate of target position at the end of each submovement along the axis of hand movement. Finally, we did not find any evidence that information regarding target acceleration is properly utilized in the production of submovements.
我们研究了手臂运动的运动学特征及其与以广泛速度和加速度移动的刺激之间的关系。目标以恒定加速度、恒定减速度或恒定速度移动0.5 - 2.0秒，直到到达需要拦截的位置。对于快速移动的目标，受试者产生具有对称钟形速度曲线的单次运动。相比之下，对于缓慢移动的目标，手部速度曲线显示出多个峰值，这表明存在一种控制机制，可根据目标运动特征产生一系列离散的子运动。为了分析这些子运动的时间和空间方面如何受到目标运动的影响，我们根据最小加加速度模型将垂直手部速度曲线分解为钟形速度脉冲。子运动的数量大致与运动时间成正比，从而产生相对恒定的子运动频率（约2.5赫兹）。另一方面，子运动起始异步性显示出比子运动间隔更大的变异性，这表明子运动起始在持续时间较长的子运动之后延迟更多。对子运动幅度及其与目标运动的关系进行检查发现，受试者主要通过产生一系列子运动来实现拦截，这些子运动将使手部在每个子运动结束时沿手部运动轴的位移与目标位置的一阶估计成比例。最后，我们没有发现任何证据表明在子运动产生过程中正确利用了有关目标加速度的信息。
