Neural Engineering researchers at Huntington Medical Research Institutes in Pasadena, California, have been chosen by the Defense Advanced Research Projects Agency (DARPA) to develop a better interface between the brain and prosthetic limbs.
DARPA, the Department of Defense research and development office, has been faced with a continual challenge regarding prosthetics used by wounded war fighters returning from combat. Today’s best prosthetics have low functionality, and DARPA seeks to upgrade to models with greater dexterity and brain communication capability.
That’s where researchers of HMRI’s Neural Engineering Department come in. They will determine why current brain interfaces to prosthetics fail over a relatively short time, usually a month or two.
Once that has been determined, HMRI researchers hope to enable control of complex arm prosthetics by the brain to boost capability from 2 degrees of movement to 22 degrees, increasing elbow and wrist rotation and finger movements for greater facility in picking up objects, and keep that ability for years.
In a recent clinical trial, “intracortical electrodes that could eventually be used for these complex robotic arms have shown to be unreliable even though they showed some promise,” said Dr. Martin Han, the primary investigator on the project, working with Dr. Douglas McCreery, director of HMRI’s Neural Engineering Program, and Dr. Victor Pikov.
This project is a natural for HMRI’s Neural Engineering researchers. Established in 1970, the multi-disciplinary program’s goal is design, development and evaluation of implantable devices for functional electrical stimulation to replace impaired function of the nervous system.
The HMRI program has internationally recognized expertise in evaluating the safety of the electrode-tissue interface, a major factor in the success of implantable neural prostheses such as those that could potentially be used by amputees.
This is the first time the Neural Engineering Program has submitted a proposal to DARPA, and it’s not surprising HMRI won the contract.
By incorporating four widely used electrode designs into a hybrid array, the Investigators propose to determine why the microelectrodes fail to record neuronal action potentials over long periods of time.
Researchers have been trying to answer the question “Why do these devices fail?” “However, different researchers have used different surgical techniques, and different devices implanted into different brain regions,” Han said.
“Whenever these neurons fire, they tell these devices what to do. It’s very critical. When you lose that interface, you lose function,” he explained.
“That interface” between neurons and prosthetic device is created when a microelectrode is implanted into the brain to record and decode its instructions to control the device. The microelectrode can be as thin as a single strand of hair and made of metal or metal-like silicon, though HMRI’s neural engineers have created thinner, more flexible polymer models.
In this project, instead of stimulating neurons to fire, the microelectrodes “wait” for the neurons to transmit information that will drive a prosthetic arm in a certain way, for example, direction and velocity of movement.
Some prosthetic arms are currently attached to muscle groups that govern movement. Implantable microelectrodes transmitting directly from neurons could offer users greater control and natural movement.
Findings from this study could go beyond prosthetics to applications for other neurological disorders, including Parkinson’s disease and epilepsy, Han added.
“This could be used for detecting epileptic seizures,” he explained. “Before a major onset of an epileptic seizure, there’s known to be some subtle brain activity that’s hard to detect with current technologies, but with these electrodes in the brain, they can detect the pending onset of a seizure before it happens.”
This work is sponsored by the Defense Advanced Research Projects Agency (DARPA) Microsystems Technology Office (MTO), under the auspices of Dr. Jack W. Judy (firstname.lastname@example.org) as part of the Reliable Neural Technology Program, through the Space and Naval Warfare Systems Command (SPAWAR) Systems Center (SSC) Pacific grant No. N66001-11-1-4010.