People paralysed by spinal injuries may one day be helped by brain implants that can seek out and detect the firing of single neurons. In an experiment on monkeys, the implants have restored muscle control to animals that had been temporarily paralysed with anaesthetic.
A spinal injury or stroke can cause paralysis by blocking signals from the motor cortex to the muscles it controls. Despite the injury, the motor cortex鈥檚 neurons remain active, and experiments in other monkeys have shown that it is possible to decode the signals generated by bunches of neurons and use them to control computer cursors and robotic arms. Unfortunately, the algorithms required to do the decoding have required considerable development and computing power.
Now physiologist Chet Moritz and colleagues at the Washington National Primate Research Center in Seattle have developed a technique that could allow people to regain control of their own limbs, without the need for complex decoding algorithms (Nature, ). Their idea was to tap individual motor cortex neurons, rather than groups of them, and route control signals directly to muscles.
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To test this, they fitted two macaques with implants that had 12 independently moveable 50-micrometre-wide electrodes. They then anaesthetised the nerves supplying the muscles in the macaques鈥� wrists, and fed the signals from the implant directly to electrodes attached to the muscles. Despite the nerve block, the monkeys were able to tense these muscles as they tried to reach for a tasty reward.
The Human Brain 鈥� With one hundred billion nerve cells, the complexity is mind-boggling. Learn more in our cutting edge special report.
