DEVELOPMENT OF A NEXT GENERATION OF AN ARTIFICIAL EXTREMITY SYSTEM CAPABLE OF GENERATING AND GIVING ARTIFICIAL SENSATIONS TO SUBJECTS WITH HIGH-GRADE REALITY

这个项目的目标是开发一种人工手臂系统，能够感知机械刺激，然后将这些刺激转移到受试者身上，使受试者体验到刺激，就像相应的躯体感觉一样。我们使用的技术包括电刺激感觉神经纤维，每个感觉神经纤维根据人工臂上传感器的输出支配单个机械感受器单位。将一个钨微电极经皮插入正中神经，并固定在可以记录单个SA机械感受器单位活动的点上。然后在相同的微电极上使用250μ秒持续的方波脉冲进行电微刺激。以不同的方式改变刺激脉冲的幅度和频率，并用…分析微电刺激的性质与诱发的压力感觉的强度和面积之间的定性和定量关系有更多的研究。本实验采用心理物理方法(如极限法、调整法、升降法等)对诱发的压力感的主观强度进行了定量评估，为了使这项技术在临床上能够被接受，需要同时刺激大量和各种神经纤维。我们还研究了当同时对多个感觉神经纤维分别支配不同的单一机械感受器单位进行电刺激时，诱发的感觉及其投射面积是如何受到影响的。结果，诱发的压力感觉的主观幅度似乎与频率的正功率有关；然而，电刺激的幅度基本上没有改变。投射面积既不受幅度的影响，也不受频率的影响。关于同时刺激多个感觉神经纤维，目前的结果表明，两个机械感受器单元同时电刺激时所产生的感觉分别是关于投射面积、感觉种类和大小的简单相加，没有出现“非线性”现象。根据这些结果，我们利用上述相同的技术开发了一个人工手臂系统的原型。机器人手系统(具有人类手的形状)被用作人工手臂系统；其手指和手掌在与受试者手的投影区域(即单个机械感受器单元产生感觉的区域)相对应的区域上覆盖一层导压橡胶。然后对压力传导橡胶施加压力；微型计算机使用压力传导橡胶的输出电压来确定刺激感觉神经纤维的电脉冲的频率，然后这些电脉冲通过钨微电极输出到感觉神经纤维。受试者用滑动体积等描述由刺激引起的感觉的主观强度；将这些主观评价及其随时间的变化与施加在机械手的导压橡胶上的刺激强度进行比较。系统以令人满意的方式工作，受试者可以在相应的区域感受到施加在机械手的导压橡胶上的压力所产生的压力感觉。施加在导压橡胶上的压力与诱发感觉的主观强度之间也有很好的相关性。较少

The goal or this project was to develop an artificial arm system capable of sensing mechanical stimuli and then transferring these stimuli to the subject so that the subject experiences the stimuli as the corresponding somatic sensations. The technique we used consisted of electrically stimulating sensory nerve fibers, each of which innervates a single mechanoreceptor units, in accordance with the output of the sensors on the artificial arm.A tungsten microelectrode was inserted percutaneously into the median nerve, and fixed at a point where the activities of a single SA mechanoreceptor unit could be recorded. Electrical microstimulation was then performed with the same microelectrode using square-wave pulses of 250 μsec duration. The amplitude and the frequency of the stimulation pulses were altered in various ways, and qualitative and quantitative relationship between the properties of the micro-electrical stimulation and the intensities and areas of the evoked pressure sensations w … More ere studied. In this trials, the subjective intensities of the evoked pressure sensation were evaluated quantitatively by means of psychophysical methods (such as method of limits, method of adjustment, or up-and-down method.In order for this technique to be acceptable for actual clinical use, it is necessary to stimulate both a large number and various kinds of nerve fibers simultaneously. We investigated also how an evoked sensation and its projected area are affected when electrical stimulation is given simultaneously to multiple sensory nerve fibers each of which separately innervate different single mechanoreceptor unit.As a result, the subjective magnitude of the evoked pressure sensation was appeared to be related to a positive power of the frequency ; however, there was essentially no change in the amplitude of the electrical stimulation. The projected area was affected neither by the amplitude nor the frequency. With regard to simultaneous stimulation of multiple sensory nerve fibers, results so far indicated that the sensation evoked when two mechanoreceptor units underwent simultaneous electrical stimulation became a simple addition concerning the projected areas, kinds of sensation, and the magnitude, respectively, and no "non-linear" phenomena took place.According to these results, we developed a prototype of an artificial arm system using the same technique as stated above. A robot hand system (with the shape of a human hand) was used as an artificial arm system ; its fingers and palm was covered with a sheet of pressure-conductive rubber over the area corresponding to the projected area of the subject's hand (i.e. the area over which the single mechanoreceptor unit produces a sensation). Pressure was then applied to the pressure-conductive rubber ; a microcomputer used the output voltage of the pressure-conductive rubber to determine the frequency of the electrical pulses for stimulating the sensory nerve fiber, and these electrical pulses were then output to the sensory nerve fiber via the tungsten microelectrode. The subjective intensities of the sensations evoked by the stimulation were described by the subjects using a slide volume, etc. ; these subjective evaluations and their changes with respect to time were compared with the strengths of the stimuli applied to the pressure-conductive rubber of the robot hand.The system worked in a satisfactory manner, and the subjects could feel the pressure sensation at the corresponding area resulting from the pressure that was applied to the pressure conductive-rubber of the robot hand. There was also a good correlation between the pressure applied to the pressure-conductive rubber and the subjective intensities of the evoked sensations. Less