Published: April 13, 2022 By

To really understand how the brain works, you need to see it in action.

Researchers at the University of Colorado Boulder and Anschutz Medical Campus are exploring several imaging techniques aimed at creating miniature microscopes that are lightweight enough to be worn by freely moving mice as they navigate a maze or socialize with other mice.

The complementary projects are a first step toward unraveling some of the biggest neuroscientific mysteries, from how animals track smells to make decisions to how the brain heals itself after experiencing damage.

Both techniques are part of a longstanding collaboration among four researchers – Juliet Gopinath and Victor Bright at CU Boulder, and Diego Restrepo and Emily Gibson at CU Anschutz – as well as many postdoctoral researchers and graduate students in their respective labs.

“The results of the project have been enabled by a wonderful interdisciplinary collaboration between electrical and mechanical engineering, bioengineering and neuroscience,” Gopinath said.

SIMscope 3D tech specs
  • Electrowetting lens and onboard CMOS
  • Structured illumination for rejection of out-of-focus and scattered light
  • Captures 3D images at depths up to 120 micrometers in awake mice

Read the paper

The first technique, recently spotlighted by Optica, focuses on eliminating out-of-focus and scattered light that occurs when a microscope shines through biological tissue.

With that SIMscope3D microscope, researchers have successfully captured 3D images of microglia cells in action, said lead author and CU Boulder postdoc Omkar Supekar. Microglia cells help maintain the health of the nervous system by removing damaged neurons.

“For someone with a traumatic brain injury, you could see the microglial cells going around fixing other cells,” said Supekar. “To the best of our knowledge, there’s no other microscope that can do this.”

He added that the microscope does not use any specialized parts, which would make it cheaper to manufacture. The next step in the project, being facilitated by a National Institutes of Health grant, will focus on making the microscope lighter and faster.

“Microglial changes are pretty slow – on the order of minutes or hours,” Supekar said. “We want to look at neurons firing in the brain in real time.”

STED microscope tech specs
  • Two-photon (2P), fiber-coupled, stimulated emission depletion microscope
  • 2P excitation light (915 nm) and donut-shaped depletion beam (592 nm)
  • First demonstration of MEMS mirror scanning in a STED system, first bend-insensitive 2P fiber STED microscope and first demonstration of a 2P fiber microscope for super-resolution imaging of mammalian cells

Read the paper

The second technique is enabling super-resolution microscopy that could help get a better glimpse of those neurons. Published in APL Photonics, recent improvements to the system include doubling the number of photons used to excite fluorescence and using an infrared laser to image deeper into tissue than was possible in a previous proof-of-concept.

“With this, we can look at structures on the scale of a hundred nanometers or a little bit less than that,” said lead author Brendan Heffernan, who completed his PhD in 2021 in Gopinath’s lab. “That’s the size of sub-features of neurons, like the way neurons connect at synapsis, or also even possibly studying how the proteins and molecules move around inside of the cell.”

Heffernan, who now works as a research scientist at IMRA America, said being part of such a collaborative lab with multiple interests helped to give him a leg up in his career.

“The field that I’m working in now is more focused on very small structures, like patterning glass on a micron scale,” he said. “I didn’t actually do any of that in grad school, but Juliet’s lab had an effort in those types of areas. So I had some understanding of those techniques.”