Aurora is an elegant, quick-minded participant in a research project for improving the lives of people paralysed by illness or injury. She is not exactly a researcher, though, but an adept macaque monkey taking part in a startling series of experiments by Miguel Nicolelis and his team at Duke University’s Center for Neuroengineering, North Carolina.
The monkey sat in front of a TV monitor and learnt to use a joystick that directs a cursor on the screen to a target. Each time she succeeded, Aurora was rewarded with a drink of juice.
Then Prof Nicolelis played a little trick on her, disconnecting the joystick from the cursor. What’s more, she did not know that the area of her brain that controls movement was connected to a robot arm that could manipulate the joystick instead.
However, Aurora soon learnt not use her hand to direct the cursor and, astonishingly, if she just thought about moving it, the robot arm would oblige. Therefore, a mere intention in Aurora’s brain could, by neuroelectronic engineering, be converted into prosthetic action: mind over matter.
Equally, if not more, amazing is that the electrodes implanted in Aurora’s Motor cortex area of the brain were passing on information from only about 100 individual nerve cells – neurones.
The cortical activity regulating all movement may take place in a neural system consisting of many millions of cells, each connected to thousands of others. But a fairly basic hand or arm motion, sufficient to play a simple video game, seems to be driven and controlled by far fewer cells.
Prof Nicolelis says: “It’s a bit like an opinion poll which determines the intentions of millions of people by sampling just a couple of thousand individuals. We think the brain in real time does something similar, sampling and recruiting a relatively small number of neurones for the motor task.”
The implications of this and other experiments involving primates are profound. First, they suggest that, for all its extraordinary richness and complexity, the brain may operate on simple, universal principles. “There may be in neuroscience a grand Theory of Everything – just as physicists believe may operate in the world of atoms and particles”.
This might sound fanciful until you contemplate the endless variety of musical experience – in terms of style, texture, tempo and colour – that can be generated by the same old instruments in a typical orchestra. Understanding the timing, intensity and content of neuronal interactions that shape our thoughts and behaviour is akin to deconstructing the notes of the brain’s score.
The second implication will interest doctors faced with the problem of finding ways to make life better for paralysed patients. If you can tap the movement areas of a monkey’s brain to drive a robotic arm, why not do something similar for humans? There are many conditions, caused by disease or trauma in which the brain is intact at the level of intending to move but unable to deliver messages to arms or legs. Using stem cell techniques, some researchers are exploring ways of restoring movement by repairing damaged spinal tissue. The monkey experiment approach tackles spinal damage differently, by bypassing the neural transmission fault and linking the brain directly to prosthetic limbs.
At Brown University, Rhode Island, the director of the Brain Science Program John Donohue and his team have made extraordinary strides in that direction with a tetraplegic patient called Matthew Nagle, a 25-year-old who was paralysed from a knife wound that severely damaged his spinal cord.
He now sits in a specially adapted wheelchair. In his brain lies a tiny bed of microelectrodes, covering an area about a quarter of your little fingernail, which captures the electrical output from his motor cortex. A wire runs from the electrodes to a small capstan-like protuberance on the top of his head, connected by wire to a computer.
By thinking about moving icons across the screen, Matthew can interact with the world. He can control the channel switch and volume controls on his television, play video games, access e-mails and even draw crude shapes on the screen.
By combining this technology with high-tech Prosthesis engineering, Prof Donohue has enabled Matthew to manipulate a robot hand. He thinks “open, close and grip” and the hand obeys. It is eerily stunning to watch and marks the beginning of a new era whereby fairly simple movement instructions from the brain can be augmented by clever engineering to drive sophisticated motor actions.
In the future it may be possible to boost performance further, using robotic vision and touch to let a wheelchair patient move around, avoiding obstacles without needing to have tight movement control from the brain. Therefore, a patient might gain independence and social interactivity with surprisingly little input from the motor cortex, boosted by a lot of input from the neuroengineer.
Today’s device is relatively clumsy. The wires are visible and the control mechanisms bulky. However, Arto Numenko of the Brown University team is working towards packaging all the existing, external paraphernalia into hidden microminiature devices that shuttle messages from the brain to prosthetic limbs by wireless. No prototypes yet exist, but it is just a matter of time.
Meanwhile, five other patients are coming on stream to use the current technology. Clunky it may be but, as Prof Donohue says: “I’ve come to learn over the years that, for a severely paralysed patient, even a tiny increase in function means a great deal in terms of improved quality of life”.
Frontiers on neuroprosthetics, will be presented by Peter Evans on Radio 4, April 13 at 9pm
