Designing Brain Implants to Detect More and Last Longer

Inside the biomedical electronics lab at GE Global Research in Niskayuna, New York, Jeff Ashe, a principal engineer, holds up a mechanical pencil and points to its thin graphite point. That, he says, is the size of the new wireless brain implants GE is developing. The hope is that smaller, more biocompatible implants will help the paralyzed walk and provide a more effective way to treat diseases that affect the brain.

Neuroscientists have implanted such devices in the brains of several paralyzed patients (see “The Thought Experiment”). But today’s implants are not practical solutions. They capture only a crude picture of activity inside the brain, and they invariably begin to fail after a year or two, in large part because brain tissue begins encapsulating them in scar tissue. The software that interprets signals from the implants has gotten much better in recent years, but the implants themselves have changed little.

Some of the implants under development at GE should be about the same size as the neurons they’re measuring. According to Andrew Schwartz, a professor of neurobiology at the University of Pittsburgh, there is good evidence that making them so small will minimize the scarring. The implants are also being designed to have 10 times as many electrodes, so they will be able to record from thousands of neurons instead of just a couple of hundred. They should be wireless, too, eliminating the hardwired electrical connections that often fail and can cause infection.

GE is testing a variety of approaches for growing very thin electrodes on top of microchips, using its expertise in fabricating microelectromechanical devices (MEMs). The company thinks its experience with wireless medical devices and electronics could also help. Materials for coating the devices, which could help them last longer in the brain, are being tested now.

Existing implants, about the size of a thumbtack, have allowed a dozen or so patients to control a cursor or a robot arm just by thinking about it. This week researchers at Ohio State University reported that an implant that detects electrical activity in neurons, paired with a device that conveys electrical signals to a paralyzed arm, allowed a patient to move his hand by the power of thought.

GE is collaborating with John Donoghue, a neuroscientist at Brown University who is pioneering the use of implants as aids to paralyzed patients. The medical-device maker Medtronic and a few startups are working on better implants as well.