Nowak Dennis A, Hermsdörfer Joachim
Department of Neurology & Clinical Neurophysiology and Clinical Neuropsychology Research Group, Academic Hospital München - Bogenhausen, Technical University of Munich, Munich, Germany.
Eur J Neurosci. 2003 Nov;18(10):2883-92. doi: 10.1111/j.1460-9568.2003.03011.x.
We examined whether self-generated weight changes are anticipated by adequate grip force adjustments when repeatedly lifting an instrumented manipulandum. Subjects lifted a cup filled with 500 mL of water prior to and following drinking two portions of water with a straw without touching it. One half of the subjects drank from and lifted an uncovered cup receiving constant visual information about its filling level and the other half of the subjects drank from a covered cup without such visual feedback. During the lifts immediately following the drinking procedures, grip force scaling was erroneously programmed for the heavier weight of the preceding lift as was obvious from an inadequately high rate of grip force development. Vision had only a minor influence on the rate of grip force increase. The influence of vision on the scaling of peak grip force was more pronounced. More accurate force scaling was obtained with an increasing number of lifts performed under each weight condition, indicating an ongoing force adjustment process probably based on sensory feedback. We conclude that self-generation of a change in the weight of an object to be lifted is not, in itself, sufficient to elicit a predictive grip force output. Rather, accurate feedback information associated with the self-generated weight change is essential to update internal models related to the mechanical object properties. This assumption was confirmed in pilot experiments; when subjects lifted the cup after having poured water from it, they accurately scaled their fingertip force to the self-produced weight change. Here, direct sensory feedback from the grasping fingers could signal the weight change and update internal models while pouring water from the cup. Our data support the hypothesis that the sensorimotor system planning and processing predictive fingertip force can operate independently of higher-level cognitive and perceptual systems.
我们研究了在反复提起装有仪器的操作手柄时，自我产生的重量变化是否会通过适当的握力调整来预期。受试者在用吸管喝了两份水且不接触杯子之前和之后，提起一个装有500毫升水的杯子。一半受试者从一个无盖杯子喝水并提起它，能持续看到杯子里水的液位信息，另一半受试者从一个有盖杯子喝水，没有这种视觉反馈。在喝水过程之后紧接着的提起动作中，握力缩放被错误地设定为前一次提起时较重重量的情况，这从握力发展速度过高就可以明显看出。视觉对握力增加的速度只有轻微影响。视觉对峰值握力缩放的影响更为显著。在每种重量条件下进行的提起次数增加时，能获得更准确的力缩放，这表明可能基于感觉反馈存在一个持续的力调整过程。我们得出结论，要提起物体时自身产生的重量变化本身并不足以引发预测性的握力输出。相反，与自身产生的重量变化相关的准确反馈信息对于更新与机械物体属性相关的内部模型至关重要。这一假设在预实验中得到了证实；当受试者从杯子中倒出水后再提起杯子时，他们能根据自身产生的重量变化准确地缩放指尖力。在这里，从抓握手指传来的直接感觉反馈可以在从杯子倒水时发出重量变化的信号并更新内部模型。我们的数据支持这样的假设，即感觉运动系统规划和处理预测性指尖力可以独立于高级认知和感知系统进行操作。
