Restoration of grasp following paralysis through brain-controlled stimulation of muscles

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Abstract

Patients with spinal cord injury lack the connections between brain and spinal cord circuits that are essential for voluntary movement. Clinical systems that achieve muscle contraction through functional electrical stimulation (FES) have proven to be effective in allowing patients with tetraplegia to regain control of hand movements and to achieve a greater measure of independence in daily activities1,2. In existing clinical systems, the patient uses residual proximal limb movements to trigger pre-programmed stimulation that causes the paralysed muscles to contract, allowing use of one or two basic grasps. Instead, we have developed an FES system in primates that is controlled by recordings made from microelectrodes permanently implanted in the brain. We simulated some of the effects of the paralysis caused by C5 or C6 spinal cord injury3 by injecting rhesus monkeys with a local anaesthetic to block the median and ulnar nerves at the elbow. Then, using recordings from approximately 100 neurons in the motor cortex, we predicted the intended activity of several of the paralysed muscles, and used these predictions to control the intensity of stimulation of the same muscles. This process essentially bypassed the spinal cord, restoring to the monkeys voluntary control of their paralysed muscles. This achievement is a major advance towards similar restoration of hand function in human patients through brain-controlled FES. We anticipate that in human patients, this neuroprosthesis would allow much more flexible and dexterous use of the hand than is possible with existing FES systems.

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Figure 1: Brain-controlled FES.
Figure 2: Grasp-related raw data collected during normal conditions.
Figure 3: Grasp performance during four consecutive brain-controlled FES trials.
Figure 4: FES used to produce controlled palmar grasp force during the palmar grasp task.

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Acknowledgements

This work was supported in part by grant NS053603 from the National Institute of Neurological Disorders and Stroke to L.E.M. and a post-doctoral fellowship from the Fonds de la Recherche en Santé du Québec to C.E., with further support from the Chicago Community Trust through the Searle Program for Neurological Restoration at the Rehabilitation Institute of Chicago. We also acknowledge the technical assistance of D. Tyler and K. Kilgore as well as the surgical assistance of J. Ko and S. Paisley Agnew.

Author information

L.E.M. conceived, designed and supervised the basic experiments. C.E. and E.R.O. performed the experiments. M.J.B. carried out software development. C.E. analysed the data and prepared figures. L.E.M. and C.E. wrote the manuscript.

Correspondence to L. E. Miller.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Methods and Results, and Supplementary Figures 1-5. (PDF 418 kb)

Supplementary Movie 1

This movie shoes several examples of Monkey T executing the ball grasp experiment during FES and catch trials. (MOV 3319 kb)

Supplementary Movie 2

This movie shows several examples of Monkey J executing the ball grasp experiment during normal, FES and catch trials. (MOV 3899 kb)

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