Biological roots for teen risk-taking: Uneven brain growth

Date:
September 9, 2020
Source:
University of Delaware
Summary:
Why do some adolescents take more risks than others? Research
suggests that two centers in the brain, one which makes adolescents
want to take risks and the other which prevents them from acting
on these impulses, physically mature at different rates and that
adolescents with large differences in the rate of development
between these two brain regions are more likely to be risk-takers.



FULL STORY ==========================================================================
As any parent will tell you, no two children behave in exactly the same
way. It is part of what makes each individual unique.


==========================================================================
So, why do some adolescents take more risks than others? University of Delaware Biomedical Engineer Curtis Johnson and graduate student Grace
McIlvain think they may have an idea.

The part of the brain that makes adolescents want to take risks is
called the socioemotional system. The brain's cognitive control center, meanwhile, is what helps prevent adolescents from acting on these
impulses.

In a recently published paper in NeuroImage, Johnson and McIlvain
suggest that these two centers in the brain physically mature at
different rates and that adolescents with large differences in the
rate of development between these two brain regions are more likely
to be risk-takers. Further, the research team theorizes that it is
the brain's fundamental structure that drives these risk- taking and
control tendencies.

What makes this study unique is that the UD researchers and their
collaborators used a technique called magnetic resonance elastography
(MRE) to safely measure the mechanical properties of the brain tissue as a measure of brain development, rather than activation of those two regions.



========================================================================== Elastography is a method of imaging mechanical properties of tissues using
a magnetic resonance imaging (MRI) scanner. Simply put, the researchers
take snapshots of how the brain deforms -- or bends -- as it is vibrated
under low frequencies, and then put those images through a specific
algorithm to reverse engineer what is happening. Johnson explained
that MRE vibration is safe for all ages and provides less movement than naturally occurs in the brain. It also offers less vibration than other
devices designed for children, such as vibrating rockers.

Johnson likened the process to any other material testing and said the
research team's knowledge of how tissue deforms helps them interpret what
is happening under different vibrations. In adults, MRE techniques have
become popular for studying diseases, such as Alzheimer's, with research showing relationships between memory and cognitive performance.

"MRE techniques do not replace other aspects of studying brain
development, but they may provide a more sensitive, objective way to
look at the brain's wiring," said Johnson, an assistant professor in
the Department of Biomedical Engineering.

Mapping adolescent brain development This is not the first time that researchers have looked at how two brain regions interact to form a
certain output. But most of this work has been done using functional MRI (fMRI), where study participants are placed in the scanner and given a real-time task, and the researchers watch which areas of the brain light
up to determine what areas of the brain relate to that task.



========================================================================== Johnson's research group was an early pioneer in using MRE techniques
to make high-resolution three-dimensional maps that enable scientists to
look at specific regions of the brain. The intensity of every 3D pixel in
an image has meaning. For example, bright colors indicate high stiffness, which, in this case, indicates a measure of developmental maturity.

Looking at these features of the brain in their work, the researchers
found that it wasn't the socioemotional or the cognitive control center
alone, but the combination of the two centers of the brain working
together at a specific age or point in time that was the definitive
factor in risk taking.

"So, there is this period during adolescence where the part of the brain
that makes you want to take risks is more mature than the part of the
brain that suppresses those impulses," said McIlvain, who began working
on the project as an undergraduate summer researcher in 2016 and is now
a third-year doctoral student in biomedical engineering.

"If we can identify individuals who are more likely to take risks,
based on the biological composition of their brain, or maybe groups
of individuals, it might inform strategies for prevention." Prior to
this project, little MRE research had measured brain stiffness in
children. Earlier work in 2018 by McIlvain showed the outside of the
brain appears softer in adolescents than adults, whereas the inside of the brain appears stiffer in adolescents than adults. According to Johnson,
this aligns with the known developmental trajectory where the inside of
the brain develops first and the outside, the cortex, develops later.

The work grew out of Johnson's previous collaborative research with
Eva Telzer, a psychology professor at University of North Carolina and co-author of the paper, and leverages the advanced MRI capabilities
at UD's Center for Biomedical and Brain Imaging. Today, researchers in
the Johnson lab develop all aspects of this MRE technique, from how to
safely vibrate the head in the scanner to how to write the software to
acquire the data to methods for turning the data into images that are translated into mechanical properties.

While the research team's previous work has shown differences in the brain function of typically developing children and those with conditions,
such as cerebral palsy, this is the first time the researchers have
shown a relationship with function in healthy children. But there are
still more questions than answers.

For example, Johnson said currently there are no good measures for saying
when the brain is mature or even for how to define brain health. And
while the research team has made connections between how stiffness of the adolescent brain's socioemotional system and cognitive control center interrelate and support risk taking, there are other things they don't
know, like how these regions of the brain are affected by things like socioeconomic status, early life trauma or early education.

A big focus of the work is making the MRE scan faster. The scan
currently takes over six minutes, which can be difficult for children
with disabilities or those who are very young.

"We'd like to complete the scan in under a minute -- less time than half
a song from a Disney movie -- before a child loses interest and thinks
about moving," said Johnson.

Next steps in the research include scanning kids as young as age 5,
including those with autism. The hope is to create a robust data set
to explore how brain mechanical properties change from age 5 to age 30, generally considered to be the end of adolescence. Among other things,
they hope to use this data to better understand how children with
disabilities fit into that developmental curve.

"Right now, there is no standard way to diagnose autism, no targeted
treatment plan or metrics for measuring whether intervention is helping,"
said McIlvain, who recently was awarded an National Institutes of Health fellowship to study brain stiffness in children with autism. "If we can understand how the mechanical properties of the brain are affected in
someone with autism, we can start to answer some of those questions."

========================================================================== Story Source: Materials provided by University_of_Delaware. Original
written by Karen B.

Roberts. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Grace McIlvain, Rebecca G. Clements, Emily M. Magoon, Jeffrey M.

Spielberg, Eva H. Telzer, Curtis L. Johnson. Viscoelasticity of
reward and control systems in adolescent risk taking. NeuroImage,
2020; 215: 116850 DOI: 10.1016/j.neuroimage.2020.116850 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200909115318.htm

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