Move the square with your mind Stanford University School of Medicine
Three people with paralysis have learned to type by thought alone using a brain implant聽鈥 at the fastest speeds recorded using such a system.
Two have motor neurone disease, also known as ALS 鈥 a degenerative disorder that destroys neurons associated with movement 鈥 while the other has a spinal cord injury. All three have weakness or paralysis in all of their limbs. There is a chance that those with ALS will eventually lose the ability to speak, too, says , a neurosurgeon at Stanford University Medical Center in California.
People who have lost the ability to talk may be offered devices that allow them to select letters on a screen using head, cheek or eye movements. This is how Stephen Hawking communicates, for example. But brain-machine interfaces are also being developed in the hope that they may one day be a more intuitive way of communicating. These involve reading brain activity, either externally or via an implant embedded in the brain, and turning it into a signal that can be used to direct something in the environment.
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At the moment, these devices are a little slow. Henderson and his colleagues wanted to make a device that was quicker and easier to use than those currently in trials.
Picking up speed
First the team placed a silicone patch, covered in a hundred tiny probes, onto a region of their volunteers鈥 brains called the primary motor cortex. This area is responsible for movement. The implant was then connected to a computer, via a wire.
As a participant thought about moving different body parts, the team鈥檚 computer translated the associated brain activity into movements of a cursor on a screen. By improving the speed at which the computer could decode the brain activity, the team was able to minimise the time between thought and cursor movement. 鈥淎s we learn more about how the motor cortex works, we can create decoders that are better at approximating a person鈥檚 intent,鈥 says Henderson.
Within a day, the participants learned to control the cursor well enough to select letters and type words on a screen. On average, the volunteers were able to type between six and eight words a minute. 鈥淚t鈥檚 two to four times faster than what was previously achieved [using a brain-machine interface],鈥 says Henderson. He says they are approaching half the speed at which a person with no motor disability would physically text.
Fastest brain typing yet Stanford University School of Medicine
The three volunteers were pleased with the device (see box, below):聽鈥淭his is like one of the coolest video games I鈥檝e ever gotten to play with,鈥 says Dennis DeGray. 鈥淎nd I don鈥檛 even have to put a quarter in it.鈥 Another said it was 鈥渜uite intuitive鈥.
鈥淭his device is great,鈥 says 聽at the University of Chicago in Illinois. 鈥淭he most impressive thing is the number of characters they could type per minute.鈥澛燘ut he says the device will have to be more durable and portable before it can be made commercially available. 鈥淧ersonally, I鈥檇 want something wireless, and proven to last for a long time,鈥 he says.
For now, the brain-machine interface is only an experimental device. Henderson and his team will continue to test and develop it in other people with paralysis.
eLife
What it鈥檚 like to type with my thoughts
鈥淚 have no function below my collar bones,鈥 says John Gardener*, who damaged his spinal cord in a fall 10 years ago. 鈥淚 rely on devices,鈥 he says.
Gardener, who lives in California, is unable to move any of his limbs. Although he is able to communicate by speaking, he is not able to use voice commands to do everything he wants to do on a computer, such as move a cursor or respond to emails. Instead, he uses an eye-tracking device to do these things. Gardener was keen to volunteer for a trial of a device that would make these tasks easier for him and others in similar situations. The device, developed by a collaboration called 鈥淏raingate鈥 together with researchers at Stanford University, uses an implant to record brain activity. This then feeds a signal, through a wire, to a computer (see main story).
Gardener had the implant surgically placed onto his brain under anaesthetic, and felt no pain afterwards. The most testing part of the procedure was having the mount for the external components of the device screwed into his skull. 鈥淚t was the sound, and the feeling of vibration, like someone was using a power drill,鈥 he says.
Once Gardener had recovered from surgery, the team was able to train the device to recognise patterns of brain activity that appeared when Gardener thought about moving his limbs. This activity could then be used to direct a cursor on a screen.
Gardener鈥檚 first task was to move the cursor to a specific target. 鈥淲hen I first tried, the cursor wiggled and fell to the bottom of the screen,鈥 he says.
Gardener learned to control the cursor by imagining his hand on top of a ball, rolling it one way or another. He quickly got the hang of it. When faced with a keyboard he was able to move the cursor across the screen to the desired letter and select it by thinking about clicking his fingers.
At the end of the first training session, Gardener was able to type on average 8.5 words per minute. 鈥淚t鈥檚 at least five times as fast as the system I鈥檝e been using,鈥 he says.
His existing system is called a 鈥淪martNav鈥 鈥 essentially a pair of glasses that monitors his head movements to allow him to control the movement of a cursor on a screen. But sending emails isn鈥檛 easy, says Gardener. 鈥淎 short 20-word email takes 15 minutes,鈥 he says.
At the moment, his brain implant is only being used for research. Before such devices hit the general market, they will have to be cordless, and be less labour intensive to set up.
The first of such devices will probably help people with paralysis to communicate, but others might help them control robotic limbs, or aspects of their home environment.
*Name has been changed
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