New insights on brain development sequence through adolescence
Brain maturation sequence renders youth sensitive to environmental
impacts through adolescence

Date:
April 10, 2023
Source:
University of Pennsylvania School of Medicine
Summary:
Brain development does not occur uniformly across the brain, but
follows a newly identified developmental sequence, according to
a new study.

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,
rendering youth sensitive to socioeconomic environments through
adolescence.


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FULL STORY ========================================================================== Brain development does not occur uniformly across the brain, but
follows a newly identified developmental sequence, according to a new
Penn Medicine study. 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, rendering
youth sensitive to socioeconomic environments through adolescence. The
findings were published recently in Nature Neuroscience.


========================================================================== Researchers charted how developmental processes unfold across the human
brain from the ages of 8 to 23 years old 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 capacity for neural circuits -- connections
and pathways in the brain for thought, 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 reductions in plasticity occur in the brain throughout
childhood and adolescence.

The findings reveal that reductions in brain plasticity occur earliest in "sensory-motor" regions, such as visual and auditory regions, and occur
later in "associative" regions, 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 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. A
lot of neuroscientists' understanding about brain plasticity during
development actually comes from studies conducted with rodents. But
rodent brains do not have many of what we refer to as the association
regions of the human brain, so we know less about how these important
areas develop," said corresponding author Theodore D. Satterthwaite,
MD, the McLure Associate Professor of Psychiatry in the Perelman School
of Medicine at the University of 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 to youth MRI imaging insights. Prior research examining how neural circuits behave when they are plastic uncovered
that brain plasticity is linked to a unique pattern of "intrinsic"
brain activity.

Intrinsic activity is the neural activity occurring in a part of the brain
when it is at rest, or not being engaged by external stimuli or a mental
task. When a brain region 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 more neurons in the region
are active, 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 synchrony, the sound level of the orchestra increases, and
the amplitude of the sound wave gets higher," said first author Valerie Sydnor,a Neuroscience PhD student. "Just like decibel meters can measure
the amplitude of a sound wave, the amplitude of intrinsic brain activity
can be measured with functional MRI while kids are simply resting in the scanner. This allowed our team to study a functional marker of brain
plasticity safely and non-invasively in youth." Analyzing MRI scans
from more than 1,000 individuals, the authors found that the functional
marker of brain plasticity declined in earlier childhood in sensory-motor regions but did not decline until mid-adolescence in associative regions.

"These slow-developing associative regions are also those that are vital
for children's cognitive attainment, social interactions, and emotional
well- being," Satterthwaite added. "We are really starting to understand
the uniqueness of human's prolonged developmental program." "If a brain
region remains malleable for longer, it may also remain sensitive to environmental influences for a longer window of development," Sydnor said.

"This study found evidence for just that." The authors studied
relationships between youths' socioeconomic environments and the same functional marker of plasticity. They found that the effects of the
environment on the brain were not uniform across regions nor static
across development. Rather, the effects of the environment on the brain
changed as the identified developmental sequence progressed.

Critically, youths' socioeconomic environments generally had a larger
impact on brain development in the late-maturing associative brain
regions, and the impact was found to be largest in adolescence.

"This work lays the foundation for understanding how the environment
shapes neurodevelopmental trajectories even through the teenage years,"
said Bart Larsen, PhD, a PennLINC postdoctoral researcher and co-author.

Sydnor elaborated, "The hope is that studying developmental plasticity
will help us to 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 youths' socioeconomic environments 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 the National Science Foundation Graduate Research Fellowship (DGE-1845298).

Additional support was provided by the Penn-CHOP Lifespan Brain Institute
and the Penn Center for Biomedical Image Computing and Analytics.

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========================================================================== Story Source: Materials provided by University_of_Pennsylvania_School_of_Medicine. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Valerie J. Sydnor, Bart Larsen, Jakob Seidlitz, Azeez Adebimpe,
Aaron F.

Alexander-Bloch, Dani S. Bassett, Maxwell A. Bertolero, Matthew
Cieslak, Sydney Covitz, Yong Fan, Raquel E. Gur, Ruben C. Gur,
Allyson P. Mackey, Tyler M. Moore, David R. Roalf, Russell
T. Shinohara, Theodore D.

Satterthwaite. Intrinsic activity development unfolds along
a sensorimotor-association cortical axis in youth. Nature
Neuroscience, 2023; 26 (4): 638 DOI: 10.1038/s41593-023-01282-y ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/04/230410132201.htm

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