summary: In adolescents, brain regions associated with emotional, social, and cognitive functions appear to be more malleable, or flexible, than other brain regions, making young adults more sensitive to social and economic environments throughout adolescence.
source: University of Pennsylvania
Brain development does not occur uniformly across the brain, but rather follows a newly identified developmental sequence, according to a new study in Penn Medicine.
It appears that regions of the brain that support cognitive, social and emotional functions remain resilient — or able to change, adapt and rebuild — longer than other brain regions, making young adults sensitive to the social and economic environments during adolescence.
The results were recently published in Natural neuroscience.
The researchers charted how developmental processes unfold across the human brain from ages 8 to 23 through magnetic resonance imaging (MRI). The findings suggest a new approach to understanding the order in which individual brain regions show a decrease in plasticity during development.
Brain plasticity refers to the ability of neural circuits—the connections and pathways in the brain for thinking, emotion, and movement—to change or reorganize in response to internal biological signals or the external environment. While it is generally understood that children have higher brain plasticity than adults, this study provides new insights into where and when declines in brain plasticity occur throughout childhood and adolescence.
The results reveal that declines in brain plasticity occur earlier in “sensory-motor” areas, such as the visual and auditory areas, and occur later in “associative” areas, such as those involved in higher-order thinking (problem solving and social learning). As a result, brain regions that support executive, social, and emotional functions appear to be particularly plastic and responsive to the environment during early adolescence, as plasticity occurs later in development.
“Studying brain development in the living human brain is challenging. Much of what neuroscientists understand about brain plasticity during development actually comes from studies in rodents,” said corresponding author Theodore D. Perelman School of Medicine at the University of Pennsylvania, and director of the Ben Livesban Center for Neuroinformatics and Neuroimaging. (PennLINC).
To address this challenge, the researchers focused on comparing insights from previous rodent studies to young adults’ insights into MRI scans. Previous research examining how neural circuits behave when plastic has revealed that brain plasticity is linked to a unique pattern of “internal” brain activity. Intrinsic activity is the neural activity that occurs in a part of the brain when it is at rest, or not engaged by external stimuli or a mental task.
When a brain region is less developed and more flexible, there is more intrinsic activity within the region, and that activity also tends to be more synchronous. This is because more neurons in the area are active, and they tend to be active at the same time. As a result, measurements of brain wave activity show an increase in amplitude (or height).
Imagine that individual neurons within a region of the brain are like musical instruments in an orchestra. First author Valerie Sydnor said: PhD student in neuroscience.
“Just like decibel meters can measure the amplitude of a sound wave, the amplitude of intrinsic brain activity can be measured using fMRI while children are simply resting in the scanner. This allowed our team to safely and non-invasively study a functional marker of brain plasticity in young adults.”
Analyzing MRI scans of more than 1,000 individuals, the authors found that the functional marker of brain plasticity decreased in early childhood in sensorimotor areas but did not decrease until mid-adolescence in associative areas.
“These slow-developing associative regions are also the ones that are vital for children’s cognitive achievement, social interactions, and emotional well-being,” added Satterthwaite. “We’re really beginning to understand the uniqueness of the prolonged human developmental program.”
“If a brain region remains flexible for a longer period, it may also remain sensitive to environmental influences for a longer period of development,” Sydnor said. “This study found evidence of just that.”
The authors examined the relationships between youth’s socioeconomic environments and the functional plasticity marker itself. They found that the environment’s effects on the brain were not uniform across regions and were not consistent across development. Instead, the environment’s effects on the brain changed as specific developmental sequences progressed.
Crucially, the social and economic environments of young people in general had a greater effect on brain development in late-maturating associative brain regions, and the effect was found to be greatest in adolescence.
“This work lays the groundwork for understanding how the environment shapes neurodevelopmental pathways even during the teenage years,” said Bart Larsen, PhD, postdoctoral researcher and co-author on PennLINC.
Sydnor explained, “We hope that studying developmental resilience will help us understand when environmental enrichment programs will have a beneficial effect on each child’s neurodevelopmental trajectory. Our findings support that programs designed to mitigate disparities in young people’s socioeconomic environments remain important for brain development throughout adolescence.” .
Funding: This study was supported by the National Institute of Health (R01MH113550, R01MH120482, R01MH112847, R01MH119219, R01MH123563, R01MH119185, R01MH120174, R01NS060910, R01EB022573, RF1MH116920., RF1MH121867, R37MH125829, R34DA050297, K08MH120564, K99MH127293, T32MH014654). The study was also supported by a Graduate Research Fellowship at the National Science Foundation (DGE-1845298).
Additional support was provided by the Penn-CHOP Lifespan Brain Institute and the Penn Center for Biomedical Image Computing and Analytics.
About this research on brain plasticity news
author: Eric Horvath
source: University of Pennsylvania
communication: Eric Horvath – University of Pennsylvania
picture: The image is in the public domain
Original search: Closed access.
“Development of intrinsic activity unfolds along the sensorimotor-associative cortical axis in youth” by Valerie Sydnor et al. Natural neuroscience
The development of intrinsic activity unfolds along the sensorimotor cortical axis in youth
Animal studies of neurodevelopment have shown that recordings of intrinsic cortical activity progress from synchronous, high amplitude to sporadic, low amplitude with decreased plasticity and cortical maturation.
Leveraging resting-state functional magnetic resonance imaging (fMRI) data from 1033 young men (8–23 years of age), we found that this stereotyped refinement of endogenous activity occurs during human development and provides evidence for a cortical gradient of neurodevelopmental change.
The decrease in the amplitude of intrinsic fMRI activity began heterogeneously across regions and was associated with maturation of intracortical myelin, a developmental regulator of plasticity. Spatiotemporal variability in regional developmental pathways was regulated along a cortical-hierarchical cortical sensorimotor cortex from ages 8 to 18 years.
Furthermore, the sensorimotor correlation axis captured the variance in correlations between the youth’s neighboring environments and intraocular fMRI activity. The associations indicate that the effects of environmental damage on the mature brain diverge further along this axis during mid-adolescence.
These findings reveal a pyramidal neuronal developmental axon and provide insights into the development of cortical plasticity in humans.