Scientists Uncover Hidden Fiber Networks Inside Human Tissues

A simple light-based method is uncovering hidden fiber networks inside the brain and body, even in tissue slides over 100 years old.

Every organ in the human body is built around networks of microscopic fibers that quietly guide how tissues work. In muscles, these fibers channel physical force. In the intestines, they support movement through the digestive system. In the brain, fiber pathways carry signals that allow different regions to communicate and support thinking and memory. Together, these tiny structures help organs function properly and maintain their shape.

Damage to these fiber networks plays a role in nearly every disease. In the brain, this damage shows up as disrupted connections between neurons, a defining feature of all neurological disorders.

Even though these fibers are central to health and disease, studying them has been difficult. Their small size and complex orientations inside tissues have made them hard to visualize using existing imaging tools.

A Simple Way to Reveal Invisible Microstructure

A research team led by Marios Georgiadis, PhD, instructor of neuroimaging, has now developed a straightforward and affordable technique that brings these hidden fiber structures into view with remarkable precision.

The approach, described in Nature Communications, is called computational scattered light imaging (ComSLI). It allows scientists to map the orientation and organization of tissue fibers at micrometer resolution on virtually any histology slide, regardless of how the sample was stained, stored, or preserved — even if it is many decades old.

Michael Zeineh, MD, PhD, professor of radiology, is a co-senior author of the study along with Miriam Menzel, PhD, a former visiting scholar in Zeineh’s lab.

“The information about tissue structures has always been there, hidden in plain sight,” Georgiadis said. “ComSLI simply gives us a way to see that information and map it out.”

Why Existing Imaging Methods Fall Short

Common techniques for imaging tissue fibers come with important limitations. MRI is useful for viewing large-scale brain networks, but cannot capture fine cellular detail. Traditional histology approaches often depend on specialized stains, costly equipment, and carefully maintained samples. They also struggle to clearly resolve areas where fibers intersect.

ComSLI overcomes these issues by relying on a basic physical behavior of light. When light passes through microscopic structures, it scatters in ways that depend on the orientation of those structures. By rotating the direction of illumination and measuring how scattering patterns change, researchers can determine fiber directions within each tiny pixel of an image.

The experimental setup is simple, requiring only a rotating LED light source and a microscope camera. Computer algorithms then process subtle variations in scattered light to generate color-coded maps known as microstructure-informed fiber orientation distributions, which show both fiber direction and density.

Works on Almost Any Tissue Slide

One of ComSLI’s most powerful features is its flexibility. The technique works on formalin-fixed, paraffin-embedded sections, the most common type used in hospitals and pathology labs. It also performs well on fresh-frozen tissue, as well as stained and unstained samples.

Researchers can even return to slides created for unrelated studies, including specimens stored for decades, and extract new structural information without altering the samples.

“This is a tool that any lab can use,” Zeineh said. “You don’t need specialized preparation or expensive equipment. What excites me most is that this approach opens the door for anyone, from small research labs to pathology labs, to uncover new insights from slides they already have.”

Revealing Brain Microstructure and Disease Effects

Mapping the brain’s microscopic wiring has long been a major goal in neuroscience. Using ComSLI, Georgiadis and colleagues were able to visualize entire formalin-fixed, paraffin-embedded human brain sections, as well as standard-sized slides, revealing fine structural details across different brain regions.

The researchers also examined how fiber patterns change in neurological conditions such as multiple sclerosis, leukoencephalopathy, and Alzheimer’s disease.

They paid particular attention to the hippocampus, a deep-brain region critical for forming and retrieving memories and often affected early in neurodegenerative disease. By comparing hippocampal tissue from a person with Alzheimer’s disease to tissue from a healthy individual, the team observed pronounced structural damage. Fiber crossings that normally link different parts of the hippocampus were greatly diminished, and a key pathway responsible for carrying memory-related signals into the hippocampus — the perforant pathway — was barely visible. In contrast, the healthy hippocampus displayed a dense and interconnected web of fibers throughout the region. These detailed images allow scientists to visualize how memory circuits deteriorate over time.

To further test the method, the team analyzed a brain section prepared in 1904. Despite its age, the sample still revealed complex fiber pathways when examined with ComSLI, demonstrating the technique’s ability to extract new insights from historical specimens.

Expanding Beyond Brain Research

Although ComSLI was originally designed for studying the brain, the researchers found that it works equally well in other tissues. They applied the method to samples from muscle, bone and blood vessels, each showing distinct fiber arrangements tied to specific biological functions.

In tongue muscle, the technique revealed layered fiber patterns associated with flexibility and movement. In bone, it traced collagen fibers aligned with mechanical stress. In arteries, it exposed alternating layers of collagen and elastin fibers that contribute to both strength and elasticity.

By making it possible to map fiber orientation across different organs, species and archival samples, ComSLI could change how scientists study tissue structure and function. It also transforms millions of stored slides worldwide into valuable sources of previously inaccessible data.

“Although we just presented the method, there are already multiple requests for scanning samples and replicating the ComSLI setup — so many labs and clinics would like to have micron-resolution fiber orientation and micro-connectivity on their histology sections,” Georgiadis said. “Another exciting plan is to go back to well-characterized brain archives or brain sections of famous people, and recover this micro-connectivity information, revealing ‘secrets’ that have been considered long lost. This is the beauty of ComSLI.”

Reference: “Micron-resolution fiber mapping in histology independent of sample preparation” by Marios Georgiadis, Franca auf der Heiden, Hamed Abbasi, Loes Ettema, Jeffrey Nirschl, Hossein Moein Taghavi, Moe Wakatsuki, Andy Liu, William Hai Dang Ho, Mackenzie Carlson, Michail Doukas, Sjors A. Koppes, Stijn Keereweer, Raymond A. Sobel, Kawin Setsompop, Congyu Liao, Katrin Amunts, Markus Axer, Michael Zeineh and Miriam Menzel, 5 November 2025, Nature Communications.
DOI: 10.1038/s41467-025-64896-9

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