Sandia, ASU researchers probe neurons' electrical signals

Researchers at Arizona State University and Sandia National Laboratories are looking to gain a better understanding of how neurons work in the interest of developing new prevention, diagnostic, and treatment techniques for brain disorders. The researchers are trying to measure and record electrical signals generated by neurons and supporting cells.

That requires accurately positioning suitably small electrodes within the brain, which is in constant movement. In addition, the nerve tissue is sensitive, and if disrupted by a foreign body—such as an electrode—will generate an immune response that masks the electrical signal of interest.

Nevertheless, Jit Muthuswamy, an associate professor of biomedical engineering at ASU Tempe, is attempting, along with researchers at Sandia, to pursue a robotic electrode system that would seek and maintain contact with neurons of interest autonomously in a subject going through normal behavioral routines.

“We are working to develop chronic, reliable, intelligent neural interfaces that will communicate with single neurons in a variety of applications, some of which are emerging and others that are closer to market,” Muthuswamy said, as quoted at Newswise. “Applications like brain prostheses are critically dependent on us being able to interface and communicate with single neurons reliably over the course of a patient’s life. Such reliable neural interfaces are also critical to help us understand the dynamic changes in the wiring diagram of the brain.”

The researchers, including Sandia engineer Murat Okandan, are employing microscale actuators to reposition the electrodes, leveraging the unique microsystems engineering capabilities available at Sandia’s Microsystems and Engineering Sciences Applications facility.

“The process flow we use to make these isn’t available anywhere else in the world, so the level of complexity and mechanical design space we had to design and fabricate these was immensely larger than what other researchers might have,” Okandan said, as reported at Newswise.

The researchers have developed a self-contained unit the size of a thumbnail that has three microelectrodes and three thermal microactuators, each of which, when subjected to a current, expands to push the microelectrodes outward. It takes 540 thermal cycles at 1,000 Hz to fully extend the microprobes.

The unit has been tested in rodents, and Muthuswamy said the neural probes demonstrated significant improvement in signal quality and reliability when controlled by the Sandia microactuators in response to loss of neural signals. He added that autonomous closed-loop controls to compensate for microscale perturbations in brain tissue significantly improve the stability of neural recordings from the brain. The microelectrodes are made of polysilicon, which is sufficiently durable for millions of cycles while providing significant signal-to-noise ratios compared with wire probes. Visit Newswise for more.

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