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Research on neural probe that sheds multicolor light on the complexities of the brain recognized for its impact

Prof. Euisik Yoon and his team are recognized for their work designing low-noise, multisite/multicolor optoelectrodes that will help neurologists learn more about neural connectivity in the brain. | Short Read
Demonstration of the Michigan Probe's multisite/multicolor optoelectrodes.

Prof. Euisik Yoon and his team have been recognized by Microsystems & Nanoengineering with an Outstanding Paper Award for their work bringing multicolor capabilities to the Michigan brain probe. The research, originally published two years ago, was recognized for its continued significance and impact.

The Michigan brain probe stimulates neurons with light, a technique known as “optogenetics.” This technique allows researchers to study the complexities of the brain’s neural networks. Yoon and his team integrated optical waveguides onto the silicon probe shank to create low-noise, multisite/multicolor optoelectrodes. These optoelectrodes can generate different colors to stimulate different responses in neurons. This can help researchers better understand the feedback effects and interconnectedness in the brain’s neural networks. It is particularly helpful for studying how memory is formed and how memory is retrieved or blocked.

“One experiment involves maintaining a blue light while increasing the intensity of a red light,” Yoon says. “This causes a negative feedback between two neurons, for the activation of one neuron from the red light can suppress the activation of a different neuron from the blue light. This can really help us map brain connectivity to improve our understanding of how the brain regulates and balances neurons.”

Prior to this design, researchers would implant part of an optical fiber directly into the test subject’s brain. These fibers required external tethering, meaning there was essentially a long fiber cord protruding from the brain, and this caused restraints when the animal moved.  The fibers were also much larger, which limited the number of fibers that could be implanted, restricting the range and type of colors that could be emitted.

Yoon’s team addressed these problems by integrating the light source directly onto the head of the probe. The probe is completely tetherless, and researchers can switch colors instantly, exciting or inhibiting a specific neuron.

“Our probe can really demonstrate the functional connectivity of different neurons,” Yoon says. “These kinds of new tools will help unravel the mystery of the brain.”

The paper is “Dual color optogenetic control of neural populations using low-noise, multishank optoelectrodes.” The team’s current goal is to make this design more easily manufacturable so it can be disseminated to the science community. The research is funded by the National Institutes of Health, and the probes were fabricated in the Lurie Nanofabrication Facility.

Hayley Hanway

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Hayley Hanway
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  • Euisik Yoon

    Euisik Yoon

    Professor, Electrical Engineering and Computer Science

The electrons absorb laser light and set up “momentum combs” (the hills) spanning the energy valleys within the material (the red line). When the electrons have an energy allowed by the quantum mechanical structure of the material—and also touch the edge of the valley—they emit light. This is why some teeth of the combs are bright and some are dark. By measuring the emitted light and precisely locating its source, the research mapped out the energy valleys in a 2D crystal of tungsten diselenide. Credit: Markus Borsch, Quantum Science Theory Lab, University of Michigan.

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