Scientists just found a way to see hidden brain changes as we age

Every heartbeat sends a ripple through the body, a pressure wave that travels from the heart to the brain, causing its arteries to expand and contract rhythmically. This subtle motion, known as cerebral arterial pulsation, has long been suspected to play a role in brain health. But until now, its secrets have remained hidden deep within the smallest vessels of the brain, beyond the reach of conventional imaging.

Now, scientists at the Mark and Mary Stevens Neuroimaging and Informatics Institute (Stevens INI) at the Keck School of Medicine of USC have developed a groundbreaking technique that allows them to see these hidden pulses in living humans. Their discovery could transform how we understand aging, dementia, and diseases like Alzheimer’s.

For decades, researchers have tried to understand how cerebroarterial pulsation affects the brain. Most studies focused on large arteries, measuring blood velocity to estimate pulsatility. However, the brain’s smallest vessels, its microvasculature, remained elusive, as their rhythmic movements were too subtle to detect without invasive methods, which are typically used only in animal studies.

That’s where the USC team stepped in. Using ultra-high field 7T magnetic resonance imaging (MRI), they introduced the first noninvasive method for measuring “microvascular volumetric pulsatility”, the expansion and contraction of tiny blood vessels in sync with the heartbeat.

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“Arterial pulsation is like the brain’s natural pump, helping to move fluids and clear waste,” said Danny JJ Wang, PhD, professor of neurology and radiology at the Keck School of Medicine and senior author of the study. “Our new method allows us to see, for the first time in people, how the volumes of those tiny blood vessels change with aging and vascular risk factors. This opens new avenues for studying brain health, dementia, and small vessel disease.”

The researchers found that microvascular pulses increase with age, particularly in the brain’s deep white matter, a region crucial for communication between brain networks. This area is particularly vulnerable to reduced blood supply from distal arteries, which carry blood to the most distant parts of the body.

As these pulses intensify, they may disrupt fluid circulation in the brain, potentially accelerating memory loss and the progression of Alzheimer’s disease.

“These findings provide a missing link between what we see in large vessel imaging and the microvascular damage we observe in aging and Alzheimer’s disease,” said lead author Fanhua Guo, PhD, a postdoctoral researcher in Wang’s lab.

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One of the most intriguing aspects of the study is its connection to the brain’s glymphatic system. This recently discovered network clears waste products, such as beta-amyloid, the protein that accumulates in Alzheimer’s disease.

Excessive vascular pulsatility may impair this system’s function, allowing toxic proteins to accumulate and hasten cognitive decline.

“Being able to measure these tiny vascular pulses in vivo is a critical step forward,” said Arthur W. Toga, PhD, director of the Stevens INI. “This technology not only advances our understanding of brain aging but also holds promise for early diagnosis and monitoring of neurodegenerative disorders.”

The USC team’s innovation combines two advanced MRI techniques, vascular space occupancy (VASO) and arterial spin labeling (ASL), to track volume changes in microvessels over the cardiac cycle. They confirmed that older adults show heightened microvascular pulsations in deep white matter compared to younger adults, and that hypertension further amplifies these changes.

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Now, the researchers are working to adapt the method for wider clinical use, including on more commonly available 3T MRI scanners. Future studies will explore whether microvascular volumetric pulsatility can predict cognitive outcomes and serve as a biomarker for early intervention in Alzheimer’s disease and related conditions.

“This is just the beginning,” Wang said. “Our goal is to bring this from research labs into clinical practice, where it could guide diagnosis, prevention, and treatment strategies for millions at risk of dementia.”

The ability to see the brain’s tiniest pulses, once invisible to science, is opening a new frontier in neuroscience. It’s a reminder that even the smallest rhythms in our bodies can hold profound clues about who we are, how we age, and how we might heal.

As researchers continue to explore this hidden heartbeat of the brain, one thing is clear: the pulse of discovery is stronger than ever.

Journal Reference:

1. Guo, F., Zhao, C., Shou, Q. et al. Assessing cerebral microvascular volumetric with high-resolution 4D cerebral blood volume MRI at 7 T. Nat Cardiovasc Res (2025). DOI: 10.1038/s44161-025-00722-1

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