Researchers at Caltech have come up with a plan to help make usable robotic limbs a reality for people who are paralyzed.
For most of us, moving our arms and legs comes naturally. These movements, like nearly everything we do, begin in the brain.
Most people don't have to give much thought to these motions. Signals from the brain travel down the spinal cord to the limbs. That is, our brains send a signal down our spinal cords and into the legs to walk, and signals travel down the spinal cord and into the arms to help us grab or throw.
This is why people who experience severe injuries along the spinal cord are often fully or partially paralyzed.
For years, scientists have tried to give people with spinal injuries the ability to use robotic limbs.
The field is called neuroprosthetics and involves implanting electrodes into a person's brain. The brain's motion signals are transmitted to a computer, which then translates it into a command, sending the signal to the robotic arm or leg.
Most commonly, the implant has been placed into the motor cortex, the portion of the brain that controls motion.
Unfortunately, those signals haven't produced the results scientists were hoping for.
Because the motor cortex handles the mechanics of movement, and not the intent of movement, it results in the prosthetic moving with a delayed, jerky motion. An arm getting instructions to drink from a glass of water might spill some or all of it in the process.
This is because when we think about doing tasks like drinking from a cup or brushing our teeth, we don't think about each individual movement involved. Instead, we think about the action itself.
This video from Caltech explains a new approach that focuses less on the mechanics and more on the intent:
Caltech's new approach seeks to solve this problem by focusing on a different part of the brain.
This part of the brain is called the posterior parietal cortex, and its job is to envision an entire action, and from what their researchers have found, it might be the key to reducing the jerky, delayed motion.
So, with the implant in the motor cortex, a person would think this...
And get this...
But with the implant in the posterior parietal cortex, a person would think this...
... and get this wonderful, smooth motion with absolutely no water spilling everywhere.
The team at Caltech put the theory to the test, placing the implant into a patient's posterior parietal cortex, and ... it totally worked.
Yes! The test subject was able to move the robotic arm using just the part of the brain that controls intent, was able to shake hands, and could even play "rock, paper, scissors" against another person.
Caltech's Professor Richard Andersen explains the test like this:
"When you move your arm, you really don't think about which muscles to activate and the details of the movement — such as lift the arm, extend the arm, grasp the cup, close the hand around the cup, and so on. Instead, you think about the goal of the movement. For example, 'I want to pick up that cup of water. So in this trial, we were successfully able to decode these actual intents, by asking the subject to simply imagine the movement as a whole, rather than breaking it down into myriad components."