Vicario D S, Ghez C
Exp Brain Res. 1984;55(1):134-44. doi: 10.1007/BF00240507.
In cats trained to track a moving display by making rapid, isometric force adjustments, responses are characterized by extremely short reaction times (60-70 ms) and a stereotyped temporal configuration. The animal uses early derivatives of display movement to scale force responses to target stimuli of different sizes according to a learned relationship between initial display motion and required force (Ghez and Vicario 1978a, 1978b). In the present study we altered that relationship by using double stimulation and delayed feedback to assess the animals' ability to update their responses. In experiments where a second target stimulus followed the first after a controlled interval (15-120 ms) on random trials, the animal modified its response in the appropriate direction with little or no increase in reaction time. When the second stimulus called for a return to baseline, the animal aborted the ongoing response. When the second stimulus called for a doubling of force, the animal increased its phasic force output; however, this increase was not sufficient to reach the new target level and late responses were emitted. The control response which followed each experimental double stimulation trial showed consistent differences from other controls in the amplitude of both peak force and peak dF/dt. Control responses following trials calling for a return were reduced in size; those following stimuli requiring response doubling were increased. We concluded that the experimental trials not only elicited modification of ongoing responses but also caused the animal to alter its internalized gain function relating initial display derivatives to required force. In experiments where feedback was delayed after giving a first target stimulus such that the compensatory display failed to reflect the animal's initial response, the animal emitted a new updated response 70-80 ms after the first. The display trajectory which caused the cat to update its response on delayed feedback trial was identical to that of control trials with long reaction times. In this case, however, the information eliciting response updating had to be derived as a difference between the actual display trajectory and that expected by the animal, based on its experience with the tracking task. This suggests that the animal develops an internal model of display properties which is used to determine when a new response is required.
在经过训练通过进行快速等距力调整来跟踪移动显示屏的猫中，其反应的特点是反应时间极短（60 - 70毫秒）且具有固定的时间配置。动物利用显示屏运动的早期导数，根据初始显示屏运动与所需力之间的学习关系，对不同大小的目标刺激按比例调整力反应（Ghez和Vicario，1978a，1978b）。在本研究中，我们通过使用双重刺激和延迟反馈来改变这种关系，以评估动物更新其反应的能力。在随机试验中，当第二个目标刺激在可控间隔（15 - 120毫秒）后跟随第一个刺激出现时，动物在适当方向上修改其反应，且反应时间几乎没有增加或没有增加。当第二个刺激要求恢复到基线时，动物中止正在进行的反应。当第二个刺激要求力加倍时，动物增加其相位力输出；然而，这种增加不足以达到新的目标水平，并且会发出延迟反应。在每次实验性双重刺激试验后的对照反应在峰值力和峰值dF/dt的幅度上与其他对照显示出一致的差异。要求恢复的试验后的对照反应大小减小；要求反应加倍的刺激后的对照反应增大。我们得出结论，实验性试验不仅引发了正在进行的反应的修改，还导致动物改变其将初始显示屏导数与所需力相关联的内化增益函数。在给予第一个目标刺激后反馈延迟的实验中，使得补偿性显示屏未能反映动物的初始反应，动物在第一个刺激后70 - 80毫秒发出新的更新反应。在延迟反馈试验中导致猫更新其反应的显示屏轨迹与具有长反应时间的对照试验相同。然而，在这种情况下，引发反应更新的信息必须从实际显示屏轨迹与动物根据其跟踪任务经验所期望轨迹之间的差异中推导出来。这表明动物建立了一个显示屏特性的内部模型，该模型用于确定何时需要新的反应。
