A few tiny LEDs could help paralyzed people move their limbs again

Mice equipped with a special light-sensitive gene can experience muscle stimulation when put in close contact with nothing more than a few tiny LEDs. It's a close match for natural muscle stimulation, and could provide a revolutionary paralysis treatment.


Stanford researchers inserted into the mice a gene harvested from algae that created light-sensitive proteins throughout the nerve cells of the mice (you can see the proteins in green, in this cross-section of a nerve). Tiny LED bands were then placed around the mice's sciatic nerves. The researchers could then use the bulbs to hit these nerves with powerful blasts of blue light, which produced muscle contractions almost indistinguishable from those the mice would have experienced naturally.

Electrical versions of this technology have been used previously to allow paralysis patients limited muscle movement, including actually being able to walk for short periods. But those devices don't work well because they activate the muscle nerves in the wrong order. The optical device fixes that.

We have two types of muscles: fast-twitch and slow-twitch. As you might imagine, slow-twitch muscles don't require as much energy, and they are used for less intense movements. The fast-twitch muscles, on the other hand, are held in reserve until a person needs to make a particularly fast or powerful muscle movement, and they're not built for long-term sustained use. The electrical "cuffs" get this exactly wrong, forcing the fast-twitch muscles to handle the walking. This resulted in a lot of fast, powerful strides, which made for a rather bizarre, disjointed gait and quickly exhausted the patients.


The optical cuffs (pictured above), on the other hand, are able to activate the slow-twitch muscles, which will allow for more natural muscle stimulation. When the researchers tested both optical and electrical cuffs on the mice, they found the optical versions allowed the muscles to retain about a third of their initial force after twenty minutes, and this remained so for quite some time after that. The electrical cuffs, on the other hand, left the mice muscles utterly exhausted after less than five minutes.

Using optical cuffs to help paralysis patients walk again is a definite possibility, although it's not without its challenges. The algae gene would need to be safely inserted into the body, and we're not entirely sure how to do that yet. There's also the question of writing some fairly sophisticated computer algorithms that would allow patients to control their movement through precisely altering the light bursts. In the meantime, the researchers are also investigating whether it's possible to produce the exact opposite effect, using light to stop muscle movement and provide a possible treatment for involuntary movement diseases like cerebral palsy.


[Nature Medicine via Technology Review]

Top image of LED throwies via Instructables.


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