Prosthetics You Can Move AND Feel

For a while now, researchers have been able to wire monkeys up with prosthetic limbs that they can control using only their brain. The monkey thinks something, electrodes implanted into the monkey brain detect specific electrical activity, and that information is transmitted to the prosthetic limb as instructions for movement. 

This is of course a pretty awesome development, but far from perfect. Most important probably is the fact that the monkeys need to have electrodes in their brains to get the best resolution of their electrical signals; this would probably not be a patient’s first choice. You can read electrical activity from outside of a person’s head, but not as well since you’re farther from the source, so control over a prosthetic limb would probably be much less fine-tuned.

A second problem is that the monkeys could move the limb but of course they couldn’t feel it, which is a pretty fundamental way that we use our bodies. We’re not constantly watching every part of us to coordinate our movement; we have to be able to feel everything. Now, monkeys with thought-controlled prosthetic limbs may be able to do this too. 

From New Scientist:

In a mind-meld between monkey and computer, rhesus macaques have learned to “feel” the texture of virtual objects without physically touching a thing. In the future, prosthetic limbs modelled on similar technology could return a sense of touch to people with amputations.

Using two-way communication between brain and machine, the monkeys manoeuvred a cursor with their minds and identified virtual objects by texture, based on electrical feedback from the computer.

Miguel Nicolelis of Duke University Medical Center in Durham, North Carolina, and his colleagues implanted electrodes into the brains of two monkeys. The electrodes recorded activity in the motor cortex and somatosensory cortex (SSC) – brain areas that orchestrate voluntary movement and sense of touch. Electrical activity from the motor cortex was sent to a computer, which translated the neural chatter into instructions that moved a cursor on screen. The monkeys learned what patterns of thought reliably changed the cursor’s position.

The team then assigned a unique texture to each of three identical circles on the screen. When the cursor hovered over each circle, the computer zapped the monkeys’ SSCs with the same electrical impulses that occurred when they touched each texture in real life. Finally, the team taught the monkeys to associate a particular texture with a reward…

Whereas typical brain-machine interfaces return some motor control to people who are paralysed or who have had amputations, brain-machine-brain interfaces could return lost sensory experience to them as well.

The motor cortex and the somatosensory cortex are two pretty important areas of the brain, sort of on the top middle of your brain. The motor cortex is important for planning motor commands that are relayed to your muscles, and the somatosensory cortex is important for receiving “touch” sensory information from everywhere in your body. By reading commands given in the motor cortex scientists can transmit motor commands to a prosthesis, and then they can transmit information from the prosthesis back into the somatosensory cortex for the monkey to “feel” it. 

This particular experiment was done with a virtual prosthesis; I imagine building a touch-sensitive robotic prosthesis will be a separate hurdle for the near future. According to LiveScience, these researchers are intent on creating an exoskeleton for paralyzed individuals that will allow them to move all of their limbs using their thoughts – and they want to do this by 2014. I seriously doubt a thought-controlled full exoskeleton will exist in any practical form by 2014, but it’s good to know that it’s something that’s seriously being worked on.


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