Mind-reading brain probe could unlock motor control for quadriplegics
By Loz Blain
September 4, 2009
While Honda is taking a benign and non-invasive approach to the coveted brain-machine interface, British researchers are experimenting with a sensor array that is actually implanted in the brain. Dr. Jon Spratley's "multi-contact brain probe" is designed to be injected into the tissue of the brain with a fine needle, where it will sit, monitoring electrical impulses across the brain's motor cortex and relaying them wirelessly to an external device. Spratley believes the technology could unlock a range of bionic possibilities for quadriplegics, who could, for example, learn to control a wheelchair or computer mouse using the same brain commands that used to operate their arms and legs.
For those of us will full use of our arms and legs, it's difficult to imagine what it must be like to be paralyzed from the neck down. Aside from the complete lack of sensation, your brain is still able to make the same commands that used to move your limbs - but nothing happens.
Several research teams around the world are looking at ways to harness these brain signals and use them to operate machinery that can help quadriplegics interact physically with the world around them. The idea of a functioning brain-machine interface would open up a range of much quicker, much more convenient interactions with computers, for example, and if the technology became refined enough it might even be able to operate robotic limbs, vehicles, and all sorts of household devices.
One research program showing promise is the PhD thesis of Dr. Jon Spratley, recently of Birmingham University and now working for Cambridgeshire's 42 Technology. As part of his Doctoral thesis, Spratley built a prototype of a multi-contact brain probe that sits inside the skull, in contact with the brain.
The probe is injected into the motor cortex of the brain - an area that is fairly well understood. The motor controls for each part of the body are mapped out in sequence along this piece of brain tissue, and the act of trying to move each muscle causes a specific part of the motor cortex to emit electrical signals that would normally propagate down through the nervous system and spinal cord to cause those muscles to operate.
Once the sensor is implanted, and its 50 tiny spikes are connected into the surrounding nerve cells, four tiny wires are unfurled that sit along the motor cortex, waiting for signals at any point along the wire. Any signal that's detected is relayed wirelessly from the sensor to a 1.6cm "base station" that's permanently mounted in the exterior skull where the needle went through.
The range of signals that are picked up from the motor cortex as the subject imagines moving various muscles can be exported from the brain in real-time and used as programmable inputs to a computer that subjects could then train themselves to control. Spratley believes his work is a step forward, as the wireless communication between the probe and its base station is less dangerous and less invasive than the wired inputs used by other projects.
The interface prototype is the first step towards a human trial - he tested the probe with slices of brain in a laboratory but no human tests have as yet been undertaken.
But between the several teams that are attacking this problem from various sides, it seems certain that before too long, this technology could start becoming very useful to a group of people who could really do with it. And of course, beyond that, it opens up possibilities of additional bionic limbs and brain-machine interfaces for the able among us, using the brain's ability to adapt to new circumstances to implant new senses and motor abilities. Exciting stuff!