Alstermark B, Isa T, Lundberg A, Pettersson L G, Tantisira B
Department of Physiology, University of Göteborg, Sweden.
Exp Brain Res. 1993;94(2):287-94. doi: 10.1007/BF00230298.
Trajectory formation of unrestrained forelimb target-reaching was investigated in relation to the effect of a change in target location. Sagittal displacement of the target (6 cm in each direction) gave a selective change of velocity in the x direction (protraction) with an increase or decrease at larger and shorter distances, respectively. In the case of a double-peaked x velocity profile, the change was mainly with respect to the first major component. The shape of the y (sideways) and of the z (lifting) velocity profiles were both almost unchanged, but the onset of the movement in the z direction changed with the x distance. Vertical displacement (4 cm up or 5 cm down) gave increased velocity in the z direction (lifting) when the target was above the normal mid-position and decreased velocity when the target was lower. The velocity was changed with constant rate of rise, so that the rise time increased when the target was elevated and shortened when the target was lowered (pulse width control policy). The change in the z velocity was not selective. In cats with a double-peaked x velocity profile, the second component decreased when the target was elevated and increased when it was lowered. With excessive lowering of the target (14 cm down), the first x velocity component was very much reduced in amplitude so that protraction depended mainly on the second x velocity component. In the cat with a unimodal x velocity profile, a second component appeared in the x and net velocity profiles when the target was excessively lowered.(ABSTRACT TRUNCATED AT 250 WORDS)
研究了无约束前肢目标导向运动轨迹的形成与目标位置变化的关系。目标的矢状位移（每个方向6厘米）分别在较大和较短距离处增加或减少时，会使x方向（前伸）的速度产生选择性变化。在双峰x速度分布的情况下，变化主要涉及第一个主要分量。y方向（侧向）和z方向（抬起）速度分布的形状几乎不变，但z方向运动的起始随x距离而变化。垂直位移（向上4厘米或向下5厘米）在目标高于正常中间位置时使z方向（抬起）的速度增加，在目标较低时使速度降低。速度以恒定的上升速率变化，因此当目标升高时上升时间增加，当目标降低时上升时间缩短（脉冲宽度控制策略）。z方向速度的变化没有选择性。在具有双峰x速度分布的猫中，当目标升高时第二个分量减小，当目标降低时第二个分量增加。当目标过度降低（向下14厘米）时，第一个x速度分量的幅度大大减小，因此前伸主要取决于第二个x速度分量。在具有单峰x速度分布的猫中，当目标过度降低时，x方向和净速度分布中会出现第二个分量。（摘要截短于250字）
