Imaging study reveals how tiny brain vessels pulse to regulate blood flow

For more than a century, scientists have known that blood vessels can rhythmically contract and relax in a process called vasomotion. In the brain, these subtle oscillations are thought to help fine-tune blood flow and may play a role in clearing waste products. Disruptions in vasomotion have been linked to disorders such as Alzheimer’s disease and stroke, but the details of how these vessel dynamics arise and spread have remained unclear.

A team at Aarhus University has now developed a new way to track vasomotion and its downstream consequences for blood flow, known as flowmotion, in awake mice. Their research is published in Neurophotonics. Using laser speckle contrast imaging (LSCI)—a technique that measures blood flow across wide areas of brain tissue with high precision—the researchers were able to capture these fleeting events in real time. They combined the imaging with advanced data analysis, including wavelet transforms to detect oscillations, a “pulsatility index” to map arteries and veins, and clustering algorithms to separate bursts of activity from quiet periods.

Their experiments revealed that vasomotion does not occur continuously. Instead, it comes in bursts, or “flares,” lasting on average about 80 seconds, followed by equally long silent intervals. The strongest oscillations originated from the walls of small arteries, where vessel diameter fluctuated rhythmically. These oscillations in diameter then propagated downstream as rhythmic changes in blood flow, reaching veins after a short delay of about a third of a second.

The findings support the idea that arterial walls are the main drivers of vasomotion in the brain and that this rhythmic activity spreads through the vascular network rather than appearing everywhere at once. By uncovering these transient patterns, the study provides new insights into how the brain regulates blood supply on a fine scale.

Commenting on the work, Alberto L. Vasquez at the University of Pittsburgh’s Center for Neuroscience remarks, “The work by Drs. Skøtt, Matchkov, and Postnov used laser speckle contrast imaging to show the amplitude and frequency changes of slow vascular pulsations in the awake mouse brain. It reveals vascular locations where these fluctuations are relatively large, potentially suggesting a control location and how other locations within the same vessel react and experience these changes.” Vasquez adds, “This is a clever use of LCSI to capture these dynamics at high resolution from the rodent brain.”

Beyond the immediate results, the work highlights the value of LSCI combined with advanced analysis for studying complex vascular dynamics. A clearer understanding of vasomotion may shed light on its role in maintaining brain health—and how its breakdown could contribute to diseases marked by impaired blood flow and waste clearance.

For details, see the original Gold Open Access article by M. V. Skøtt, V. Matchkov, and D. D. Postnov, “Arterial-wall origin and transient dynamics of flow- and vaso-motion activities in the awake mouse brain revealed by laser speckle contrast imaging,” Neurophotonics 12(S2), S22804 (2025), doi: 10.1117/1.NPh.12.S2.S22804.

The article appears in the Neurophotonics special issue “Imaging Brain Metabolism and Neuroenergetics” (in progress), edited by Ghazaleh Ashrafi (WashU Medicine), Prakash Kara (University of Minnesota), and Alberto L. Vasquez (University of Pittsburgh).