In a new study published in The Lancet Digital Health, scientists at the USC Mark
and Mary Stevens Neuroimaging and Informatics Institute (Stevens INI) have discovered that the brains of people who experience severe
physical impairment after a stroke may reorganize themselves in unexpected
ways, showing signs of “younger” brain structure in undamaged regions as they
adapt to injury.
The international research effort is
part of the Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Stroke
Recovery Working Group, which analyzed brain scans from more than 500 stroke
survivors across 34 research sites in eight countries. Using deep learning
models trained on tens of thousands of MRI scans, the researchers estimated the
“brain age” of different regions in each hemisphere to see how stroke damage
affects brain structure and 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 of the study. “This pattern suggests the
brain may be reorganizing itself, essentially rejuvenating undamaged networks
to compensate for lost function.”
The research team used an advanced form
of artificial intelligence known as a graph convolutional network to predict
the biological age of 18 brain regions from MRI data. The difference between a
person’s predicted brain age and their actual chronological age, known as the
brain-predicted age difference (brain-PAD), served as a sensitive marker of
neural health.
When the team associated these
measurements with motor performance scores, they found a striking pattern:
stroke survivors with severe movement deficits, even after more than 6 months
of rehabilitation, showed younger-than-expected brain age in regions opposite
the lesion, particularly within the frontoparietal network, a key system
involved in motor planning, attention, and coordination.
“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,” Kim explained. “We saw this in the
contralesional frontoparietal network, which showed a more ‘youthful’ pattern
and is known to support motor planning, attention, and coordination. 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.”
The study was conducted through ENIGMA,
a global alliance that unites data from more than 50 countries to better
understand the brain across diseases. Researchers harmonized MRI data and
clinical measures across dozens of cohorts to build the world’s largest stroke
neuroimaging dataset of its kind.
“By pooling data from hundreds of stroke
survivors worldwide and applying cutting-edge AI, we can detect subtle patterns
of brain reorganization that would be invisible in smaller studies. These
findings of regionally differential brain aging in chronic stroke could
eventually guide personalized rehabilitation strategies,” said Arthur W. Toga, PhD, director of the Stevens INI and Provost Professor at USC.
The team plans to expand their work to
include longitudinal studies tracking patients from the acute to chronic stages
of stroke recovery. By observing how patterns of brain aging and reorganization
develop over time, clinicians might be able to customize interventions based on
each patient’s unique neural adaptation process, ultimately improving recovery
outcomes and quality of life in the near future.
Source: Stroke triggers a hidden brain change that looks like rejuvenation – Scents of Science
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