On Friday the New York Times reported that scientists at the University of Pittsburgh are ready to start clinical trials of two different brain implant systems, known as brain machine interfaces, that aim to give quadriplegic patients control over a prosthetic limb.
In the main project a team led by Professor Andrew Schwartz and Professor Michael Boninger will, over the next two years, place two sensors, each of which consists of an array of 100 electrodes that record the activity of about 50 nerve cells, just beneath the skulls of three patients. The signals collected from these sensors should allow the patients to control the movement of a prosthetic arm and hand. In 2008 Professor John Stein wrote an article for Speaking of Research on the monkey studies that Prof. Schwartz performed while developing these sensors. In these studies the monkeys displayed a finer degree of dexterity in manipulating a robotic arm than the scientists had anticipated, and learned to use the robotic arm surprisingly quickly, suggesting that paralysis victims may also be able to learn to use the prosthetic arm in a relatively short space of time.
The smaller project uses an alternative approach called electrocorticography, which also used a sensor implanted under the skull, but measures the activity of populations of nerve cells rather than individual neurons. This technique has the advantage of being less invasive than the electrodes that need to make direct contact with neurons, as the risk of infection is reduced when the protective meninges are not penetrated during implantation of the sensor. Although it was previously thought to be a less precise approach than the direct measurment of single neuron activity, a recent monkey study has demonstrated that brain machine interfaces based on electrocorticogram sensors can rival the performance of sensors that measure neuron activity directly, this and other studies have prompted the clinical evaluation of this approach.
Interesting as these trials are, they represent only a few of the technologies being developed to treat paralysis, other techniques we have examined in recent years include neuroprosthetic devices that bridge severed spinal cords, stem cells, and therapies that encourage the regrowth and repair of damaged nerve tissue. Much of this research is still at a relatively early stage, but it is exciting to see that these techniques are starting to move from the bench to the bedside.
Paul Browne
Speaking of Research 