Monkey Tests Could Help Overcome Paralysis

Dennis Faas's picture

Tests at the University of Washington have shown it's possible to reroute brain signals to move paralysed limbs. The results could eventually lead to treatment for spinal injury victims.

The study works on the idea that, although spinal injuries damage the connections which carry nerve signals, victims usually retain both the muscles in the affected limb and the use of the motor cortex, the part of the brain which controls movement. Unlike some parts of the brain, which work on a 'use it or lose it' basis, studies have shown people can retain full control over the motor cortex even after years of being quadriplegic (that is, being paralyzed in all four limbs).

The new tests, performed on monkeys, have used a device the size of a cellphone known as a brain-machine interface. It converts brain signals into an electrical impulse which, when applied to a muscle, causes contraction.

During the testing, the monkeys received a local anesthetic to cause temporary paralysis in the arm. The scientists then used the device to connect the monkeys' brains to the affected limbs. It turned out this was enough for the monkeys to tense their arm muscles by thought alone. Surprisingly, they were able to use any part of the motor cortex, not just the cells specifically designed to control arms. (Source:

It could take some time before the treatment is ready for human use. That's because the researchers will need to develop ways to distinguish different types of muscle movement to allow particular skills such as gripping or pushing. To be truly effective, the system will also have to allow accurate co-ordination of multiple muscles.

The other big problem at the moment is that the system only transmits information in one direction. That means the brain can't receive feelings from the limb, making it much more difficult to have fine control over objects. (Source:

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