Research Stories

by Melissa Crytzer-Fry

Imagine a brain implant device smart enough to maneuver around inside a person's skull. On its own, the device can locate the most functional target area to do its work. The task might involve deep brain stimulation therapy for a patient with Parkinson's disease. Or it might include powering the robotic arm of a person who has lost limb control.

Such devices are known as moveable brain implants. They are realistic, not science fiction, thanks to work by researchers in the Neural Microsystems Laboratory at Arizona State University's Fulton School of Engineering.

Medical scientists use a variety of brain implants to sense electrical and chemical activity in the brain. They can study single neurons or ensembles of neurons. But these implanted devices often fail over a period of time, according to Jit Muthuswamy, an ASU bioengineering professor.

Failure is a result of natural tissue movement or inflammation around the implant site. Drifting caused by the devices' positioning mechanisms also can contribute to movement and less-than-optimal connections between the implant and targeted neurons. The very cells that the device is seeking to connect with sometimes drift away. All of this happens as part of the body's natural defense mechanism to foreign bodies and intrusive substances.

"The real challenge is learning how to maintain a reliable interface between a single neuron and a probe," says Muthuswamy. "Very precise positioning is the key to success,"

He says that current implant fall short in this respect. They require invasive brain surgery. And they cannot be repositioned once surgically implanted into the brain.

Muthuswamy describes the devices he and his colleagues are building. "Our probes can be moved independently, using micromotors," he says. "We can reposition the electrodes precisely where we want to and have the maximum efficacy of brain stimulation."

The motorized portion of the implant is half the size of a human thumbnail. It resembles a wafer-thin microchip. It would be positioned outside the brain, possibly under or outside the skull.

"Only the probes that radiate out from the chip actually touch the brain," Muthuswamy says. He explains that a few small upward-downward correctional adjustments will generally reestablish a connection with specific neurons.

At present, doctors and physiologists would be responsible for repositioning the probes to achieve optimal outcomes. But in the future, the ASU research team thinks that microprobes will move within the brain in an autonomous fashion. They will have the ability to precisely reposition themselves when necessary.

Muthuswamy and a team of ASU researchers are also testing the devices for performance in humid environments. Chemical, electrical, and biological testing also must be completed.

"Prostheses for the retina and the cochlea, as well as emerging cortical prostheses can be powered by brain implants. Such devices are already raising exciting possibilities," says Muthuswamy. "These technologies are critically dependent on precisely sensing specific neurons of interest and maintaining connectivity with those neurons during the patient's life."

The ASU researcher thinks that brain implant research has other applications as well. Implants might enhance the efficiency of deep brain stimulation therapies for individuals suffering from Parkinson's disease or seizures. There might also be future applications for stroke victims or for individuals suffering from schizophrenia and other currently incurable brain disorders.

Brain implant research at ASU is supported by the National Institutes of Health, the Whitaker Foundation, and the Arizona Biomedical Research Commission, in collaboration with researchers from Sandia National Laboratories of New Mexico.