Brain development does not occur uniformly throughout the brain, but instead follows a newly identified developmental sequence, according to a new study from Penn Medicine. Brain regions that support cognitive, social, and emotional functions appear to remain malleable (or capable of changing, adapting, and remodeling) longer than other brain regions, making young people sensitive to socioeconomic environments during adolescence. . The findings were recently published in neuroscience of nature.
The researchers recorded how developmental processes unfold in the human brain from ages 8 to 23 through magnetic resonance imaging (MRI). The findings indicate a new approach to understanding the order in which individual brain regions show reductions in plasticity during development.
Brain plasticity refers to the ability of neural circuits, connections, and pathways in the brain for thought, emotion, and movement, to change or reorganize in response to internal biological cues or the external environment. While it is generally understood that children have greater brain plasticity than adults, this study provides new insights into where and when reductions in brain plasticity occur during childhood and adolescence.
The findings reveal that reductions in brain plasticity occur first in “sensory and motor” regions, such as visual and auditory regions, and occur later in “associative” regions, such as those involved in higher-order thinking (resolution). problems and social learning). . As a result, the brain regions that support executive, social, and emotional functions appear to be particularly malleable 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 neuroscientists’ understanding of brain plasticity during development actually comes from studies done with rodents. But rodent brains don’t have many of the association regions of the human brain, so we know less about how these important areas develop,” said corresponding author Theodore D. Satterthwaite, MD, McLure Associate Professor of Psychiatry at the University of California Perelman School of Medicine. Pennsylvania, and director of the Penn Lifespan Informatics and Neuroimaging Center (PennLINC).
To address this challenge, the researchers focused on comparing insights from previous rodent studies with insights from MRIs of young people. Previous research examining how neural circuits behave when plastic found that brain plasticity is linked to a unique pattern of “intrinsic” brain activity. Intrinsic activity is neural activity that occurs in a part of the brain when it is at rest, or when it is not involved with external stimuli or a mental task. When a region of the brain is less developed and more plastic, there tends to be more intrinsic activity within the region, and that activity also tends to be more synchronized. This is because there are more neurons active in the region and they tend to be active at the same time. As a result, measurements of brain activity waves show an increase in amplitude (or height).
“Imagine that individual neurons within a region of the brain are like instruments in an orchestra. As more instruments begin to play together in sync, the sound level of the orchestra increases and the amplitude of the sound wave increases.” said the first author. valeria sydnor,PhD student in neurosciences. “Just as decibel meters can measure the amplitude of a sound wave, the amplitude of intrinsic brain activity can be measured with an fMRI while children simply rest in the scanner. This allowed our team to study a marker function of brain plasticity safely and non-invasively in youth”.
Analyzing MRIs of more than 1,000 people, the authors found that the functional marker of brain plasticity decreased in early childhood in sensorimotor regions, but did not decrease until mid-adolescence in associative regions.
“These slow-developing association regions are also vital for children’s cognitive achievement, social interactions, and emotional well-being,” Satterthwaite added. “We are really beginning to understand the uniqueness of the long development program of the human being.”
“If a region of the brain remains malleable longer, it may also remain sensitive to environmental influences for a longer window of development,” Sydnor said. “This study found evidence of that.”
The authors studied the relationships between the socioeconomic backgrounds of young people and the same functional marker of plasticity. They found that the effects of the environment on the brain were neither uniform across regions nor static across development. Rather, the effects of the environment on the brain changed as the identified developmental sequence progressed.
Critically, the socioeconomic backgrounds of youth generally had a greater impact on brain development in late maturing associative brain regions, with the impact found to be greatest in adolescence.
“This work lays the foundation for understanding how the environment shapes neurodevelopmental trajectories even during adolescence,” said Bart Larsen, PhD, PennLINC postdoctoral researcher and co-author.
Sydnor explained: “The hope is that studying developmental plasticity will help us understand when environmental enrichment programs will have a beneficial impact on each child’s neurodevelopmental trajectory. Our findings support that programs designed to alleviate disparities in the socioeconomic environments of youth remain important for brain development throughout the adolescent period.”
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 National Science Foundation Graduate Research Grant (DGE-1845298).
The Penn-CHOP Lifespan Brain Institute and the Penn Center for Biomedical Image Computing and Analytics provided additional support.