Bertarelli Foundation Chair in Translational Neuroengineering, Centre for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
The Biorobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy.
Sci Robot. 2019 Feb 20;4(27). doi: 10.1126/scirobotics.aau8892.
Current myoelectric prostheses allow transradial amputees to regain voluntary motor control of their artificial limb by exploiting residual muscle function in the forearm. However, the overreliance on visual cues resulting from a lack of sensory feedback is a common complaint. Recently, several groups have provided tactile feedback in upper limb amputees using implanted electrodes, surface nerve stimulation, or sensory substitution. These approaches have led to improved function and prosthesis embodiment. Nevertheless, the provided information remains limited to a subset of the rich sensory cues available to healthy individuals. More specifically, proprioception, the sense of limb position and movement, is predominantly absent from current systems. Here, we show that sensory substitution based on intraneural stimulation can deliver position feedback in real time and in conjunction with somatotopic tactile feedback. This approach allowed two transradial amputees to regain high and close-to-natural remapped proprioceptive acuity, with a median joint angle reproduction precision of 9.1° and a median threshold to detection of passive movements of 9.5°, which was comparable with results obtained in healthy participants. The simultaneous delivery of position information and somatotopic tactile feedback allowed both amputees to discriminate the size and compliance of four objects with high levels of performance (75.5%). These results demonstrate that tactile information delivered via somatotopic neural stimulation and position information delivered via sensory substitution can be exploited simultaneously and efficiently by transradial amputees. This study paves a way to more sophisticated bidirectional bionic limbs conveying richer, multimodal sensations.
目前的肌电假肢允许桡骨截肢者通过利用前臂中的残余肌肉功能来重新获得对其假肢的自愿运动控制。然而，由于缺乏感觉反馈，对视觉线索的过度依赖是一个常见的问题。最近，一些小组已经通过植入电极、表面神经刺激或感觉替代为上肢截肢者提供了触觉反馈。这些方法导致了功能和假肢体现的改善。然而，所提供的信息仍然仅限于健康个体可用的丰富感觉线索的一个子集。更具体地说，本体感觉，即肢体位置和运动的感觉，在当前的系统中主要缺失。在这里，我们表明基于神经内刺激的感觉替代可以实时提供位置反馈，并与躯体感觉的触觉反馈相结合。这种方法使两名桡骨截肢者重新获得了高且接近自然的重新映射本体感觉敏锐度，关节角度再现精度中位数为 9.1°，被动运动检测的中位数阈值为 9.5°，与健康参与者的结果相当。位置信息和躯体感觉的触觉反馈的同时提供使两名截肢者能够以高水平的性能（75.5%）区分四个物体的大小和顺应性。这些结果表明，通过躯体感觉神经刺激传递的触觉信息和通过感觉替代传递的位置信息可以被桡骨截肢者同时有效地利用。这项研究为更复杂的双向仿生肢体传递更丰富、多模态的感觉铺平了道路。
