Toward the Restoration of Hand Use to a Paralyzed Monkey: Brain-Controlled Functional Electrical Stimulation of Forearm Muscles

PLoS ONE, 2009 · DOI: 10.1371/journal.pone.0005924 · Published: June 15, 2009

Simple Explanation

This research explores using brain signals to control electrical stimulation of forearm muscles in monkeys with temporary limb paralysis. The aim is to restore hand function lost due to spinal cord injuries by enabling independent control of multiple muscles for a range of tasks. The monkeys used a system with a multi-electrode array implanted in the motor cortex to control four forearm muscles. This cortically controlled functional electrical stimulation (FES) system allowed them to produce wrist force and track visually displayed targets. The study demonstrated that monkeys could significantly increase wrist force and control its magnitude and timing with reasonable accuracy, suggesting that brain-controlled FES prostheses could benefit paralyzed patients with mid-cervical spinal cord injuries.

Study Duration

5 weeks

Participants

Two rhesus macaque monkeys

Evidence Level

Level 2; Experimental study in primates

Key Findings

1
Monkeys with temporary arm paralysis were able to significantly increase their wrist flexion force using brain-controlled FES compared to their force output without FES.
2
The monkeys could control the magnitude and time course of the force produced via FES well enough to track visually displayed force targets.
3
The time to achieve success in force-tracking tasks was longer with FES than under normal conditions, primarily due to increased reaction time, rise time, and force variability.

Research Summary

The study demonstrates the feasibility of using brain-controlled functional electrical stimulation (FES) to restore voluntary control of paralyzed muscles in monkeys. The monkeys were able to use neural signals from the motor cortex to control the contraction of four forearm muscles, resulting in increased wrist force and the ability to track force targets. The findings suggest that brain-controlled FES has the potential to provide a more versatile and adaptive approach to restoring hand function in paralyzed patients compared to existing pre-programmed FES systems.

Practical Implications

Restoration of Hand Function

Brain-controlled FES could offer a new approach to restore hand use in individuals with spinal cord injuries, potentially improving their quality of life.

Advanced Neuroprosthetics

The research contributes to the development of advanced neuroprosthetic devices that can provide more natural and dexterous control of movements.

Clinical Translation

The proof-of-concept findings pave the way for future studies to translate brain-controlled FES technology into clinical applications for paralyzed patients.

Study Limitations

1
The study only controlled four muscles, limiting the complexity of movements that could be achieved.
2
The behavioral task was limited to a single degree of freedom (wrist flexion/extension), which does not fully represent the complexity of natural hand movements.
3
The FES-induced movements were slower and more variable than normal movements, indicating a need for further refinement of the control system.

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