NeurOne: High-performance Motor Unit-Computer Interface for the Paralyzed

Abstract

We have recently demonstrated that humans with motor-and-sensory complete cervical spinal cord injury (SCI) can modulate the activity of spared motor neurons that control the movements of paralyzed muscles. These motor neurons still receive highly functional cortical inputs that proportionally control flexion and extension movements of the paralyzed hand digits. In this study, we report a series of longitudinal experiments in which subjects with motor complete SCI received motor unit feedback from NeurOne. NeurOne is a software that realizes super-fast digitalization of motor neuron spiking activity (32 frames/s) and control of these neural ensembles through a physiological motor unit twitch model that enables intuitive brain-computer interactions closely matching the voluntary force modulation of healthy hand digits. We asked the subjects (n=3, 3-4 laboratory visits) to match a target displayed on a monitor through a cursor that was controlled by the modulation of the recruitment and rate coding of the spared motor units using a motor unit twitch model. The attempted movements of the paralyzed hands involved grasping and hand digit extension/flexion. The target cursor was scaled in a way that the subjects could increase or decrease feedback by either recruiting or derecruiting motor units, or by modulating the instantaneous discharge rate. The subjects learned to control the motor unit output with high levels of accuracy across different target intensities up to the maximal achievable discharge rate. Indeed, the high-performance motor output was surprisingly stable in a similar way as healthy subjects modulated the muscle force output recorded by a dynamometer. Therefore, NeurOne enables tetraplegic individuals an intuitive control of the paralyzed muscles through a digital neuromuscular system.Significance StatementOur study demonstrates the remarkable ability of individuals with complete cervical spinal cord injuries to modulate spared motor neurons and control paralyzed muscles. Utilizing NeurOne, a software, we enabled intuitive brain-computer interactions by digitalizing motor neuron spiking activity and employing a motor unit twitch model. Through this interface, tetraplegic individuals achieved high levels of accuracy and proportional control which closely resembled motor function in intact humans. NeurOne provides a promising digital neuromuscular interface, empowering individuals to control assistive devices super-fast and intuitive. This study signifies an important advancement in enhancing motor function and improving the quality of life for those with spinal cord injuries.