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Shriya S. Srinivasan is a Biomechatronics PhD student at MIT. Image: James Day/MIT

Light activation of nerves offers a new way to restore movement

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Scientists at the MIT Media Lab have developed a new optogenetic technique that could be used to restore movement in paralysis patients. The technique could also treat unwanted muscle tremor in Parkinson’s patients.

Currently, electrical stimulation of nerves is extensively used in patients with spinal cord injuries or in people with muscular degenerative diseases such as amyotrophic lateral sclerosis, or ALS. Electrical stimulation is also used to control prosthetics and paralyzed limbs.

However, such electrical stimulation of nerves causes muscle fatigue. It can also be painful and it is hard to target movement of specific muscles. The new research offers an alternative method of nerve stimulation.

MIT researchers have shown that that nerves can be made to express proteins which can be activated by light. Such activation can produce limb movements that can be controlled in real-time, using hints generated by the motion of the limb.

This movement produced by this new optogenetic technique is smoother and less exhausting than those produced by the electrical stimulation of nerves.

Previously, optogenetic techniques have been used to control nerves in the brain but this research is one of the first to control the nerves outside the brain.

This method has been tested on mice. The researchers were able to control the up and down movement of the rodents’ ankle joint by switching on an LED light source. This is the first time, a closed loop optogenetic system has been used to power a limb.

Such an optogenetic system can be a future fit for robotic exoskeletons which will allow some people with paralysis to walk, or as long-term rehabilitation tools for people with degenerative muscle diseases.

Before this technique can be used in humans, more work is required to develop ways to deliver light to nerves deep within the human body, as well as find ways to activate human nerves safely and efficiently.

The new technique was developed by Shriya S. Srinivasan, Benjamin E. Maimon, Maurizio Diaz, Hyungeun Song & Hugh M. Herr and recently published in Nature Communications.

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