Clites Tyler R, Carty Matthew J, Srinivasan Shriya, Zorzos Anthony N, Herr Hugh M
Center for Extreme Bionics, Massachusetts Institute of Technology, Cambridge, MA, United States of America.
J Neural Eng. 2017 Jun;14(3):036002. doi: 10.1088/1741-2552/aa614b. Epub 2017 Feb 17.
Proprioceptive mechanisms play a critical role in both reflexive and volitional lower extremity control. Significant strides have been made in the development of bionic limbs that are capable of bi-directional communication with the peripheral nervous system, but none of these systems have been capable of providing physiologically-relevant muscle-based proprioceptive feedback through natural neural pathways. In this study, we present the agonist-antagonist myoneural interface (AMI), a surgical approach with the capacity to provide graded kinesthetic feedback from a prosthesis through mechanical activation of native mechanoreceptors within residual agonist-antagonist muscle pairs.
(1) Sonomicrometery and electroneurography measurement systems were validated using a servo-based muscle tensioning system. (2) A heuristic controller was implemented to modulate functional electrical stimulation of an agonist muscle, using sonomicrometric measurements of stretch from a mechanically-coupled antagonist muscle as feedback. (3) One AMI was surgically constructed in the hindlimb of each rat. (4) The gastrocnemius-soleus complex of the rat was cycled through a series of ramp-and-hold stretches in two different muscle architectures: native (physiologically-intact) and AMI (modified). Integrated electroneurography from the tibial nerve was compared across the two architectures.
Correlation between stretch and afferent signal demonstrated that the AMI is capable of provoking graded afferent signals in response to ramp-and-hold stretches, in a manner similar to the native muscle architecture. The response magnitude in the AMI was reduced when compared to the native architecture, likely due to lower stretch amplitudes. The closed-loop control system showed robustness at high stretch magnitudes, with some oscillation at low stretch magnitudes.
These results indicate that the AMI has the potential to communicate meaningful kinesthetic feedback from a prosthetic limb by replicating the agonist-antagonist relationships that are fundamental to physiological proprioception.
本体感觉机制在反射性和自主性下肢控制中均发挥着关键作用。在能够与外周神经系统进行双向通信的仿生肢体开发方面已取得显著进展，但这些系统均无法通过自然神经通路提供基于肌肉的生理相关本体感觉反馈。在本研究中，我们展示了激动剂 - 拮抗剂肌神经接口（AMI），这是一种手术方法，能够通过机械激活残留的激动剂 - 拮抗剂肌肉对中的天然机械感受器，从假肢提供分级动觉反馈。
（1）使用基于伺服的肌肉张紧系统对超声测量和神经电图测量系统进行验证。（2）实施启发式控制器，利用来自机械耦合的拮抗肌的拉伸超声测量作为反馈来调节激动剂肌肉的功能性电刺激。（3）在每只大鼠的后肢手术构建一个AMI。（4）以两种不同的肌肉结构使大鼠的腓肠肌 - 比目鱼肌复合体经历一系列斜坡 - 保持拉伸：天然（生理完整）和AMI（改良）。比较两种结构下胫神经的综合神经电图。
拉伸与传入信号之间的相关性表明，AMI能够以类似于天然肌肉结构的方式，对斜坡 - 保持拉伸产生分级传入信号。与天然结构相比，AMI中的反应幅度降低，可能是由于拉伸幅度较低。闭环控制系统在高拉伸幅度时表现出鲁棒性，在低拉伸幅度时存在一些振荡。
这些结果表明，AMI有可能通过复制对生理本体感觉至关重要的激动剂 - 拮抗剂关系，从假肢传递有意义的动觉反馈。
