A new invention that’s thinner than a human hair could transform how scientists study the brain.
Researchers at Washington University in St. Louis have developed an advanced fiber-optic device capable of controlling thousands of neurons simultaneously deep inside the brain.
The breakthrough, described in Nature Neuroscience, could open new doors to understanding how complex brain circuits control thought, movement, and behavior.
The new device, called PRIME (short for Panoramically Reconfigurable IlluMinativE fiber), is a next-generation tool that combines cutting-edge optical engineering with optogenetics—a powerful technique that uses light to control neurons that have been genetically modified to respond to it.
Traditional optical fibers used in brain research can only shine light on one spot at a time. To study large brain networks, scientists would normally need hundreds of fibers, which would be far too invasive.
The PRIME fiber changes that. Using an ultrafast laser 3D microfabrication process, the engineering team led by Professor Song Hu created a single fiber filled with thousands of microscopic light emitters, each just one-hundredth the width of a human hair.
These emitters act like tiny mirrors that can direct light into many regions of the brain from a single entry point.
“By combining fiber-based techniques with optogenetics, we can achieve deep-brain stimulation at an unprecedented scale,” Hu said. “This is like having a controllable disco ball inside the brain—one that can aim light in thousands of directions.”
The project was a collaboration between Hu’s team in the McKelvey School of Engineering and Professor Adam Kepecs’ neuroscience lab at WashU Medicine. Kepecs’ group tested the new technology in animal studies, showing that PRIME could precisely manipulate neural circuits involved in instinctive behaviors.
When the team used PRIME to activate specific areas of the superior colliculus—a brain region that processes sensory information—they could reliably trigger either freezing or escape responses, depending on the light pattern used.
“This kind of tool lets us ask questions that were impossible before,” said Keran Yang, a graduate student and co-first author on the study. “By shaping light in space and time, we can explore how patterns of activity across the brain lead to specific behaviors.”
Beyond neuroscience, the technology also represents a major fabrication breakthrough. “We’re carving incredibly small light emitters into an optical fiber,” explained Shuo Yang, the postdoctoral researcher who led the device’s design.
“These tiny structures are precise and delicate, yet powerful enough to reach deep brain regions.”
Looking to the future, the team plans to make PRIME even more versatile by enabling it to stimulate and record brain activity at the same time, creating a fully bidirectional interface.
Ultimately, they hope to develop a wireless, wearable version that would allow scientists to study freely moving animals—and perhaps one day, help design new treatments for neurological disorders.
“This is just the beginning,” Hu said. “The more naturally we can study the brain, the closer we get to truly understanding how it works.”
If you care about brain health, please read studies that eating apples and tea could keep dementia at bay, and Olive oil: a daily dose for better brain health.
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