Brain Implants that Work Better and Longer

There is a problem with current brain implants: scar tissue develops around the metallic implant, attenuating the signal, shortening the useful lifespan of the device. Researchers at the University of Michigan have developed a conductive polymer coating, in the hopes that the coating will minimise scar tissue development. Such coatings may extend the useful lifespan of brain implants significantly.

"Recording quality deteriorates over time with all existing electrodes," says Andrew Schwartz, a neuroscientist at the University of Pittsburgh....

Use of devices that are surgically implanted into the brain or other parts of the nervous system is growing rapidly. Cochlear implants, which help deaf people hear, and deep brain stimulation, which relieves symptoms of Parkinson's disease, for example, are approved by the Food and Drug Administration. Both work by stimulating nerve cells via an implanted electrode. Devices that record and translate neural activity are also under development for people with severe paralysis.

But as use of neural implants grows, so does concern over the damage that those devices can impose on neural tissue. Insertion of the rigid metal electrode into soft tissue triggers a cascade of inflammatory signals, damaging or killing neurons and triggering a scar to form around the metal....Martin and his collaborators coat the electrodes with an electrically conductive polymer originally developed for electronic devices, such as organic LEDs and photovoltaics for solar cells. The polymer coating increases the surface area of the metal-biological interface, which in turn boosts performance of the electrode. "If you have lots of surface area, you can inject current more efficiently," says Douglas McCreery, director of the Neural Engineering Program at the Huntington Medical Research Institute, in Pasadena, CA. "That means less demand on batteries, but, probably more importantly, you're not recruiting the nasty electrochemical reactions that might be hazardous to surrounding tissue."

The Michigan scientists electrochemically deposit the polymer onto the electrode, much like chroming a car bumper. By peppering the material with small amounts of another polymer, they can coax the conductive polymer to form a hairy texture along the metal shaft. Martin says that the approach mimics nature: the numerous tiny alveoli of the lungs, for example, increase the surface area available for the oxygen exchange between air and blood. Scientists can also tack on nanofibers loaded with controlled-release drugs to inhibit the inflammatory reaction. _TechReview

The field of brain implants is changing rapidly. Stay updated on progress of brain-computer interfaces at Brain Stimulant blog.

Update: Streaming Video from the 38th Neural Interfaces Conference
H/T Direct Neural Interface blog (via Brainwaves)