Summary: During adolescence, brain areas that support emotion, social interaction, and complex thinking remain more plastic—more able to change and adapt—than sensory regions. This prolonged plasticity makes youth particularly sensitive to socioeconomic environments throughout adolescence.
Source: University of Pennsylvania (Penn Medicine)
New research from Penn Medicine shows that brain development follows a clear sequence rather than occurring uniformly across regions.
Using magnetic resonance imaging (MRI) to study more than 1,000 young people aged 8 to 23, researchers mapped how developmental changes in intrinsic brain activity unfold across the cortex. Their results indicate that reductions in plasticity begin earlier in sensory-motor regions (for example, visual and auditory areas) and occur later in associative regions that support higher-order thinking, social learning, and emotional processing.
Brain plasticity refers to the ability of neural circuits—networks of neurons and their connections—to change, reorganize, and adapt in response to biological maturation or environmental input. While it is well known that children generally show greater plasticity than adults, this study provides more detailed information about where and when plasticity declines across development.
The team focused on a functional marker of plasticity measured from resting-state fMRI: the amplitude of intrinsic neural activity. When a brain region is highly plastic, neurons within it tend to be more active and more synchronized, producing higher-amplitude intrinsic activity. As regions mature and plasticity declines, intrinsic activity becomes sparser and lower in amplitude.
“Recording developmental plasticity directly in the human brain is difficult, and much of our prior understanding comes from animal models,” said Theodore D. Satterthwaite, MD, McLure Associate Professor of Psychiatry at the Perelman School of Medicine and director of the Penn Lifespan Informatics and Neuroimaging Center (PennLINC). “Rodent brains lack many human association regions, so studying these processes in people fills an important gap.”
First author Valerie Sydnor, a neuroscience PhD student, explained the intuitive analogy: when more neurons in a region fire together, the resulting signal looks like an orchestra increasing in volume and synchrony. Functional MRI can measure the amplitude of that intrinsic activity while children rest quietly in the scanner, providing a safe, noninvasive marker of regional plasticity across development.
Analyzing resting-state scans from 1,033 youths, the researchers found a consistent pattern: amplitude of intrinsic activity declined earlier in sensory-motor regions and later in association regions. This heterochronous pattern mapped onto a sensorimotor–association cortical axis, revealing a hierarchical progression of maturation from lower-order sensory and motor areas to higher-order association cortex.
Because associative regions remain malleable for a longer developmental window, they may also be more responsive—positively or negatively—to environmental influences during adolescence. To test this, the team examined how youths’ socioeconomic environments related to the same functional marker of plasticity. They observed that environmental effects were not uniform: socioeconomic influences had greater impact on late-maturing associative regions, with the largest effects appearing during adolescence.
“These slow-developing associative regions are critical for cognitive achievement, social interaction, and emotional health,” Satterthwaite said. “Our results help clarify why human development is prolonged and why adolescence is a time of both opportunity and vulnerability.”
Co-author Bart Larsen, PhD, a PennLINC postdoctoral researcher, added, “This work builds a foundation for understanding how environments shape neurodevelopmental trajectories through the teenage years.” Sydnor noted that identifying when regions are most plastic can inform the timing of interventions and enrichment programs designed to reduce socioeconomic disparities in brain development.
Funding: The study was supported by multiple National Institutes of Health grants (R01MH113550, R01MH120482, R01MH112847, R01MH119219, R01MH123563, R01MH119185, R01MH120174, R01NS060910, R01EB022573, RF1MH116920, RF1MH121867, R37MH125829, R34DA050297, K08MH120564, K99MH127293, T32MH014654) and by the National Science Foundation Graduate Research Fellowship (DGE-1845298). Additional support came from the Penn-CHOP Lifespan Brain Institute and the Penn Center for Biomedical Image Computing and Analytics.
About this brain plasticity research news
Author: Eric Horvath
Source: University of Pennsylvania (Penn Medicine)
Contact: Eric Horvath – University of Pennsylvania
Image: The image is in the public domain
Original Research: Closed access. “Intrinsic activity development unfolds along a sensorimotor–association cortical axis in youth” by Valerie Sydnor et al., published in Nature Neuroscience.
Abstract
Intrinsic activity development unfolds along a sensorimotor–association cortical axis in youth
Animal studies have shown that intrinsic cortical activity transitions from synchronized, high-amplitude patterns to sparser, lower-amplitude patterns as plasticity declines and the cortex matures. Using resting-state fMRI data from 1,033 youths aged 8–23, the authors demonstrate a similar stereotyped refinement of intrinsic activity during human development and identify a cortical gradient of neurodevelopmental change.
The decline in intrinsic fMRI amplitude began at different times across regions and was linked to maturation of intracortical myelin, a regulator of developmental plasticity. Regional variability in developmental trajectories was organized along a hierarchical sensorimotor–association axis from ages 8 to 18. This axis also captured variation in associations between neighborhood socioeconomic environments and intrinsic activity, suggesting that the impact of environmental disadvantage on the maturing brain diverges most across this axis during mid-adolescence.
Overall, these results reveal a hierarchical neurodevelopmental axis and provide new insight into the timing and progression of cortical plasticity in humans.