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Tracking blood flow in the brain to understand recovery

University of Calgary researchers are using advanced imaging equipment to understand how changes in blood flow after stroke relate to brain recovery.

“I’m hoping that eventually we will be able to do a better job of evaluating how treatments are impacting blood flow and brain function together,” says neuroscientist and computer scientist Dr. Erin Mazerolle of the Healthy Brain Aging lab.

Blood delivers oxygen and nutrients to the brain to help it function properly. During a stroke, blood flow is cut off by a blockage or a ruptured blood vessel. This damage can cause loss of movement, communication, vision, and cognitive changes. As the brain heals, the brain rewires itself to try to regain lost function.

By studying changing blood flow patterns, Dr. Mazerolle and other Canadian Partnership for Stroke Recovery (CPSR) researchers in Calgary can see how the brain is reorganizing after stroke. And, eventually, they will be able to determine what kinds of treatments improve blood flow and brain function.

Another factor in post-stroke recovery is the health of blood vessels in the brain. The CPSR team in Calgary is measuring this by giving patients a tiny whiff of carbon dioxide while they undergo brain imaging. “We put a mask over their mouth and nose and give them a mixture that’s 95 per cent air and five per cent carbon dioxide,” explains Dr. Mazerolle, a post-doctoral scholar in Dr. Bruce Pike’s lab. “This increases the levels in the blood to about the same as if you held your breath for 20 seconds or so.”

Images are captured every two to four seconds to track brain blood-flow changes as they occur.

“In the healthy brain, blood vessels are very responsive to carbon dioxide so, if you get a little extra, then blood vessels expand and blood flow increases. As a person ages, blood vessels become less reactive and blood flow slows down,” Dr. Mazerolle says.

In one study, the team is working with CPSR researcher Dr. Marc Poulin to measure how exercise improves the health of blood vessels. “This reactivity measure we think is pretty sensitive to cerebrovascular health so it’s highly relevant to stroke,” she says.

They are also collaborating with CPSR research leader Dr. Sean Dukelow to do robotic assessments of patients to see how brain function and blood flow changes are associated with gains in movement, perception and vision.

“This is really new,” Dr. Mazerolle says. “People haven’t used these techniques in the stroke population.”

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