Researchers at the University of Colorado Anschutz and the University of Colorado Boulder have developed a miniature microscope that allows scientists to observe and activate individual brain cells during natural movement, an advance that could accelerate research into how the brain controls behavior while deepening understanding of neurological diseases.

These miniature microscopes have been increasingly used to study the neural basis of behavior in freely moving animals. This new microscope allows deeper penetration and higher resolution images in the brain. Importantly, it can also excite select neurons using optogenetics."

Emily Gibson, PhD, study's senior author, associate professor of biomedical engineering, CU Anschutz

The study was published online today in the journal Optica.

The new device, Opto2P-FCM, combines high-resolution brain imaging with targeted light-based stimulation in a lightweight, head-mounted microscope. Unlike previous miniature imaging systems, the new technology enables researchers to both monitor and manipulate the activity of specific neurons at the same time, providing an unprecedented view of how neural circuits function.

"This microscope is a game changer," said study co-author Juliet Gopinath, PhD, professor of electrical, computer and energy engineering and physics at CU Boulder. "Being able to demonstrate a state-of-the-art instrument for both read-out and photo-stimulation of neurons is amazing."

She noted that having the ability to study neurons with a tool like this "could yield future breakthroughs for neurological diseases and disorders."

Co-first author Mo Zohrabi, PhD, senior research scientist at CU Boulder, said the team initially thought it impossible to create such a thing "based on the tolerances of the 3D printer and optics."

"Building a complex optical device that weighs just 5 grams was challenging. Every component had to be accounted for down to the smallest tolerance," said co-first author Gregory Futia, PhD, senior research associate at CU Anschutz. "Getting all of these small optics aligned took careful mechanical design and iteration."

He noted that the work was an "interdisciplinary effort led by a team of engineers, physicists and neuroscientists who worked closely on the project."

For decades, two-photon microscopy has been considered the gold standard for producing detailed images of living brain tissue. But it usually require subjects to remain stationary, limiting researchers' ability to investigate how the brain functions during everyday activities.

While miniature microscopes have helped overcome some of those challenges, they have often sacrificed image quality or lacked the ability to precisely stimulate individual neurons.

This innovation overcomes those limitations through a novel dual-path optical design. One pathway is dedicated to producing sharp, high-resolution images, while a second delivers precisely patterned light that activates selected neurons without interfering with imaging. Separating the two functions allows each to be optimized independently, resulting in clearer images and more precise control than previous miniature systems.

"This platform gives neuroscientists an entirely new way to investigate how specific groups of neurons work together to produce behavior," Gibson said. "It opens the door to experiments that were previously very difficult-or impossible-to perform."

The researchers said this technology could become an important research tool for scientists studying disorders caused by disrupted brain circuits, including Alzheimer's disease, Parkinson's disease and epilepsy. By allowing researchers to observe and manipulate individual neurons in the same experiment, the system may help identify how healthy brain circuits function and how disease changes that.

The current device is a prototype but the study's authors are already working on future versions that will be smaller, lighter and faster while offering an even larger field of view.

"Understanding how the brain works requires more than simply watching neurons fire-we also need the ability to selectively activate specific cells and observe how the rest of the network responds," Gibson said. "Our new system gives researchers both capabilities in a compact device designed to study brain activity during natural behavior."

The study co-authors include: Gregory L. Futia, Mo Zohrabi, Connor McCullough, Alec Teel, Fabio Simoes de Souza, Ryan Oroke, Eduardo J. Miscles, Baris N. Ozbay, Karl Kilborn, Victor M. Bright, Diego Restrepo, Juliet T. Gopinath and Emily A. Gibson.