Scientists at the USC Mark and Mary Stevens Neuroimaging and Informatics Institute reported on Mar. 25 that people who experience severe physical impairment after a stroke may show signs of "younger" brain structure in undamaged regions as their brains adapt to injury. The findings come from a new study published in The Lancet Digital Health.
The research is significant because it sheds light on how the brain reorganizes itself following major injury, potentially informing future rehabilitation strategies for stroke survivors.
The international team, part of the Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Stroke Recovery Working Group, analyzed MRI scans from more than 500 stroke survivors across eight countries. Using deep learning models trained on tens of thousands of MRI scans, they estimated the "brain age" of different hemispheres to see how damage affects recovery.
"We found that larger strokes accelerate aging in the damaged hemisphere but paradoxically make the opposite side of the brain appear younger," said Hosung Kim, PhD, associate professor of research neurology at the Keck School of Medicine of USC and co-senior author. "This pattern suggests the brain may be reorganizing itself, essentially rejuvenating undamaged networks to compensate for lost function."
Researchers used artificial intelligence known as a graph convolutional network to predict biological age across 18 brain regions using MRI data. They found that stroke survivors with severe movement deficits showed younger-than-expected brain age in areas opposite their lesion—particularly within the frontoparietal network—after more than six months of rehabilitation.
Kim said, "These findings suggest that when stroke damage leads to greater movement loss, undamaged regions on the opposite side of the brain may adapt to help compensate... Rather than indicating full recovery of movement, this pattern may reflect the brain's attempt to adjust when the damaged motor system can no longer function normally. This gives us a new way to see neuroplasticity that traditional imaging could not capture."
Arthur W. Toga, PhD, director at Stevens INI and Provost Professor at USC said: "By pooling data from hundreds of stroke survivors worldwide and applying cutting-edge AI, we can detect subtle patterns... These findings... could eventually guide personalized rehabilitation strategies." The team plans further studies tracking patients over time with hopes these insights will lead to better tailored interventions for improved recovery.
