Source: Michigan State University
Why
do some babies react to perceived danger more than others? According to
new research from Michigan State University and the University of North
Carolina, Chapel Hill, part of the answer may be found in a surprising
place: an infant’s digestive system.
The
human digestive system is home to a vast community of microorganisms
known as the gut microbiome. The MSU-UNC research team discovered that
the gut microbiome was different in infants with strong fear responses
and infants with milder reactions.
These
fear responses — how someone reacts to a scary situation — in early life
can be indicators of future mental health. And there is growing
evidence tying neurological well-being to the microbiome in the gut.
The new
findings suggest that the gut microbiome could one day provide
researchers and physicians with a new tool to monitor and support
healthy neurological development.
“This
early developmental period is a time of tremendous opportunity for
promoting healthy brain development,” said MSU’s Rebecca Knickmeyer,
leader of the new study published June 2 in the journal Nature Communications. “The microbiome is an exciting new target that can be potentially used for that.”
Studies
of this connection and its role in fear response in animals led
Knickmeyer, an associate professor in the College of Human Medicine’s
Department of Pediatrics and Human Development, and her team to look for
something similar in humans. And studying how humans, especially young
children, handle fear is important because it can help forecast mental
health in some cases.
“Fear
reactions are a normal part of child development. Children should be
aware of threats in their environment and be ready to respond to them”
said Knickmeyer, who also works in MSU’s Institute for Quantitative
Health Science and Engineering, or IQ. “But if they can’t dampen that
response when they’re safe, they may be at heightened risk to develop
anxiety and depression later on in life.”
On the
other end of the response spectrum, children with exceptionally muted
fear responses may go on to develop callous, unemotional traits
associated with antisocial behavior, Knickmeyer said.
To
determine whether the gut microbiome was connected to fear response in
humans, Knickmeyer and her co-workers designed a pilot study with about
30 infants. The researchers selected the cohort carefully to keep as
many factors impacting the gut microbiome as consistent as possible. For
example, all of the children were breastfed and none was on
antibiotics.
The
researchers then characterized the children’s microbiome by analyzing
stool samples and assessed a child’s fear response using a simple test:
observing how a child reacted to someone entering the room while wearing
a Halloween mask.
“We
really wanted the experience to be enjoyable for both the kids and their
parents. The parents were there the whole time and they could jump in
whenever they wanted,” Knickmeyer said. “These are really the kinds of
experiences infants would have in their everyday lives.”
Compiling
all the data, the researchers saw significant associations between
specific features of the gut microbiome and the strength of infant fear
responses.
For
example, children with uneven microbiomes at 1 month of age were more
fearful at 1 year of age. Uneven microbiomes are dominated by a small
set of bacteria, whereas even microbiomes are more balanced.
The
researchers also discovered that the content of the microbial community
at 1 year of age related to fear responses. Compared with less fearful
children, infants with heightened responses had more of some types of
bacteria and less of others.
The
team, however, did not observe a connection between the children’s gut
microbiome and how the children reacted to strangers who weren’t wearing
masks. Knickmeyer said this is likely due to the different parts of the
brain involved with processing potentially frightening situations.
“With
strangers, there is a social element. So children may have a social
wariness, but they don’t see strangers as immediate threats,” Knickmeyer
said. “When children see a mask, they don’t see it as social. It goes
into that quick-and-dirty assessment part of the brain.”
As part
of the study, the team also imaged the children’s brains using MRI
technology. They found that the content of the microbial community at 1
year was associated with the size of the amygdala, which is part of the
brain involved in making quick decisions about potential threats.
Connecting
the dots suggests that the microbiome may influence how the amygdala
develops and operates. That’s one of many interesting possibilities
uncovered by this new study, which the team is currently working to
replicate. Knickmeyer is also preparing to start up new lines of inquiry
with new collaborations at IQ, asking new questions that she’s excited
to answer.
“We
have a great opportunity to support neurological health early on,” she
said. “Our long-term goal is that we’ll learn what we can do to foster
healthy growth and development.”
About this microbiome and neurodevelopment research news
Source: Michigan State University
Contact: Rebecca Knickmeyer & Kim Ward – Michigan State University
Image: The image is in the public domain
Original Research: Open access.
“Infant gut microbiome composition is associated with non-social fear behavior in a pilot study”
by Alexander L. Carlson, Kai Xia, M. Andrea Azcarate-Peril, Samuel P.
Rosin, Jason P. Fine, Wancen Mu, Jared B. Zopp, Mary C. Kimmel, Martin
A. Styner, Amanda L. Thompson, Cathi B. Propper & Rebecca C.
Knickmeyer. Nature Communications
