Trajectory control in targeted force impulses. VI. Independent specification of response amplitude and direction.
Trajectory control in targeted force impulses. VI. Independent specification of response amplitude and direction.
复制标题
目标力脉冲的轨迹控制。
DOI：
10.1007/bf00247934
复制
发表时间：
1989
影响因子：
2
通讯作者：
Ghez,C
中科院分区：
文献类型：
--
作者：
Favilla,M;Hening,W;Ghez,C
本系列之前的研究（Hening、Favilla 和 Ghez，1988）检查了人类受试者使用来自目标的信息来设置等长肘力脉冲幅度的过程的时间过程。在该研究中，向受试者提供了单独的提示来确定反应启动的时间，并告知他们所需的反应幅度。当目标呈现和反应启动之间的时间太短，以至于他们无法吸收来自目标的信息时，受试者会产生默认反应，其幅度反映了他们之前的经历。在较长的潜伏期中，受试者以逐渐的时间过程指定反应幅度，比平均反应时间更早开始并晚于平均反应时间结束。本研究现在研究如何在呈现目标后指定两个不同的响应特征（幅度和方向）。我们试图回答三个主要问题。在目标信息可用之前产生的响应有哪些特征？方向和幅度是串行指定还是并行指定？一个响应特征的规范是否会干扰另一个响应特征的规范？研究了六名正常受试者。他们接受训练，能够与一系列可预测的常规音调中的最后一个同步发出等长肘部力的脉冲。幅度和方向与需要屈曲或伸展的视觉目标的幅度和方向相匹配，并具有三个幅度之一。目标在最后一个音调之前的随机时间（0-400 毫秒）呈现。目标方向和幅度要么是可预测的（简单条件），要么是不可预测的（选择条件）。在简单条件下，响应幅度和方向与目标呈现和响应开始之间的间隔（S-R 间隔）无关。在选择条件下，振幅和方向均随S-R间隔变化。在短 S-R 间隔（< 100 毫秒）下，受试者反应的方向与目标的方向无关。响应的幅度接近两个目标范围的中心。随着S-R间隔的增加，正确方向反应的比例逐渐增加。在相同的S-R间隔范围内，对不同目标的正确和错误方向响应的幅度分离并收敛于各自的目标幅度。方向和幅度的规范在 S-R 间隔大于 300 ms 时完成。这种双向范例中幅度指定的时间过程比响应方向可预测的范例中的时间过程更长。正如我们之前的报告中一样，受试者通过调整力的时间导数而不是力的上升时间来改变反应幅度。屈肌、伸肌、正确方向和错误方向反应的反应轨迹相似。我们首先得出结论，即使幅度和方向都是不可预测的，对不可预测目标的脉冲响应的幅度也是从初始默认值指定的；其次，这种响应的幅度和方向是由并行运行的单独处理通道逐渐指定的；第三，然而，两个响应特征的处理并不是完全独立的。建议这两个过程共享共同的神经资源。
The preceding study of this series (Hening, Favilla and Ghez 1988) examined the time course of the processes by which human subjects use information from a target to set the amplitude of an impulse of isometric elbow force. In that study, subjects were provided with separate cues to time response initiation and to inform them of the required amplitude of the response. When the time between target presentation and response initiation was too brief for them to incorporate information from the target, subjects produced default responses whose amplitudes reflected their prior experience. At longer latencies, subjects specified response amplitude with a gradual time course, starting earlier and ending later than an average reaction time. The present study now examines how two distinct response features, amplitude and direction, are specified following presentation of a target. We sought to answer three main questions. What are the features of responses that are produced before target information is available? Are direction and amplitude specified serially or in parallel? Does the specification of one response feature interfere with the specification of the other? Six normal subjects were studied. They were trained to initiate impulses of isometric elbow force in synchrony with the last of a predictable series of regular tones. The amplitudes and directions were to match those of visual targets requiring flexions or extensions with one of three amplitudes. The targets were presented at random times (0–400 ms) before the last tone. Target directions and amplitudes were either predictable (simplecondition) or unpredictable (choicecondition). In the simple condition, response amplitudes and directions were independent of the interval between target presentation and response onset (S-R interval). In thechoice condition, both amplitude and direction varied with the S-R interval. At short S-R intervals (< 100 ms), the direction of the subjects' responses was not related to that of the target. The amplitudes of the responses were near the centers of the two target ranges. With increasing S-R intervals, the proportion of correct direction responses gradually increased. Over the same range of S-R intervals, the amplitudes of both right and wrong direction responses to the different targets separated and converged on their respective target amplitudes. Specification of both direction and amplitude was complete at S-R intervals greater than 300 ms. The time course of amplitude specification in this bidirectional paradigm was prolonged over that in a paradigm where response direction was predictable. As in our previous reports, subjects varied response amplitude by adjusting the time derivatives of force rather than force rise time. Response trajectories were similar for flexor, extensor, right and wrong direction responses. We conclude first, that the amplitudes of impulsive responses to unpredictable targets are specified from an initial default value even when both amplitude and direction are unpredictable; second, the amplitude and direction of such response are specified gradually by separate processing channels operating in parallel; third, the processing of the two response features is not, however, fully independent. It is suggested that the two processes share a common neural resource.