Interfacing spinal motor neurons in humans for the control of upper limb prostheses

Speaker: Professor Dario Farina, Department of Bioengineering, Imperial College London

Host: Dr Claudio Zito

Abstract: Alpha motor neurons are the final common pathway of the neuromuscular system since they receive synaptic input from the whole nervous system and convert it into the ultimate neural code of movement. Recently, the interfacing (bioelectrodes) and processing methods for identifying the output of motor neuron pools from interference electromyogram (EMG) signals have been advanced substantially. In the past decade, these methods have indeed allowed for the first time to monitor the behavior of tens to hundreds of motor neurons concurrently, as opposed to the classic body of knowledge of the previous 80 years based on recordings of a few (3-5) motor neurons concurrently. The identification of motor neuron population behaviors in humans, in vivo, during natural movement, has opened the possibility of using this information for man-machine interfacing. In this perspective, the muscles act as biological amplifiers of the activities of the output circuitries of the spinal cord. Moreover, when muscles are not available for recording (e.g., in amputee patients), an interfacing can still be established by surgically redirecting nerves to available muscle tissue (targeted muscle reinnervation) or to transplanted muscle tissue. The decoded motor neuron population activity can then be mapped into commands to external devices, such as prostheses. This combination of surgical procedures, advanced decoding, and mapping into effective commands constitutes a direct neural interface (since it decodes the efferent nerve activity) in a clinically viable way. The talk will overview the technology for motor neuron interfacing and the potential of motor neuron recording technology for man-machine interfacing, specifically for the control of upper limb prostheses.