A device the size of a matchstick, implanted next to the brain’s motor cortex, could one day help paralysed people move their limbs.
Researchers from the University of Melbourne have developed a new device that can be implanted into a blood vessel next to the brain's motor cortex to record high-quality neural signals. These types of signals have been successfully translated into movement commands for bionic prosthetics and exoskeletons in pre-clinical trials, and hypothetically, this sort of neural activity could be translated into commands for a variety of computer systems.
The electrode device uses a stent, or a tubular support, that holds the blood vessel open. The "stentrode" could allow people with spinal cord injuries to walk again with the help of an exoskeleton by bypassing the natural neural connections—which are damaged in the case of a spinal cord injury—and sending signals directly from the implanted device to a bionic system. The stentrode device could also help with a variety of neurological disorders such as epilepsy and Parkinson's disease, conditions that are usually combated with deep brain stimulation, a procedure that involves major brain surgery to implant a neurostimulator into the brain.
One advantage of this technique is that it doesn’t require invasive brain surgery. The research team is working to adapt the stentrode so it can provide an alternative treatment for other neurological conditions, including epilepsy, Parkinson’s disease, depression and post-traumatic stress disorder. It’s a good example of fluid and almost immediate collaboration between a human intention and an action by a digital machine.
Past research funded by DARPA—which also helped fund the development of this device—has shown that thought-controlled movement of bionic limbs can be achieved by surgically remapping the remaining nerves of a person who has lost an arm or leg. Control of a variety of computer-driven electronics has also been achieved to some extent by performing complex and dangerous open brain surgery and implanting electrodes beneath the surface of the brain.
Stentrode: Moving with the power of thought ~Credit: University Melbourne
The University of Melbourne's new brain machine interface, which is about the size of a small paperclip, can be implanted into a blood vessel near the brain in a quick and simple procedure and still measure high-quality brain signals. It also has advantages over other surgery techniques that remap nerve connections because it can accurately measure signals from the brain's motor cortex to potentially do a variety of things, not just move a prosthetic limb.
"Utilizing stent technology, our electrode array self-expands to stick to the inside wall of a vein, enabling us to record local brain activity," Dr. Nicholas Opie, a biomedical engineer at the University of Melbourne, said in a press release. "By extracting the recorded neural signals, we can use these as commands to control wheelchairs, exoskeletons, prosthetic limbs or computers."
The Royal Melbourne Hospital will carry out the procedure and recipients of the device will be selected from the Austin Health Victorian Spinal Cord Service.
"In our first-in-human trial… we are hoping to achieve direct brain control of an exoskeleton for three people with paralysis," Opie said in the press release.
The team is now planning a clinical trial at the Royal Melbourne Hospital that will start next year. Up to five patients with no use of their arms or legs due to spinal cord injury, stroke, motor neurone disease or muscular dystrophy will be involved.
The stentrode will be inserted into a blood vessel that runs along the motor cortex, the part of the brain that controls movement. Fine wires will run from the electrodes down through the blood system into a recording device implanted in the chest. This device will then wirelessly transmit the information to an external computer.
By asking participants to think about a particular action, like “move right fist”, the computer will learn to recognise the exact pattern of brain signals corresponding to each thought.“The end goal is that the person will be able to think about moving and an exoskeleton will obey,” says Grayden.
The research is exciting, but it’s still unclear whether the stentrode will be able to pick up meaningful signals in the brains of humans, says Nick Ramsey at University Medical Center Utrecht in the Netherlands. “The stentrode research is worth doing, but I would not dismiss the technologies that are already much further ahead.”
If the human trials are successful, the device could have future applications not only for prosthetics and exoskeletons, but also as a method of controlling computers through thought. Neuroscientists have been trying to connect electrical signals in the brain with electronic devices for about half a century, with early experiments demonstrating that small shocks to parts of the brain can control the behavior of animals. In the 1980s, neuroscientists discovered that they could record and analyze the firings of brain signals in monkeys to accurately predict how the animals were going to move.
Some bold experiments have also been conducted on humans in an attempt to achieve thought-controlled computers, sometimes with frightening side effects. The University of Melbourne's implantable device could potentially allow for ambitious future research in the field of thought-controlled devices without the dangers of major surgical operations on the brain.