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The human gut contains a microbial community
composed of tens of trillions of organisms that
normally assemble during the first 2–3 y of
postnatal life. Researchers at the Washington
University School of Medicine, St. Louis, propose
that brain development needs to be viewed in the
context of the developmental biology of this
“microbial organ” and its capacity to metabolize the
various diets we consume.
Scientists hypothesize that the persistent cognitive
abnormalities seen in children with undernutrition
are related in part to their persistent gut
microbiota immaturity and that specific regions of
the brain that normally exhibit persistent juvenile
(neotenous) patterns of gene expression, including
those critically involved in various higher
cognitive functions such as the brain’s default mode
network, may be particularly vulnerable to the
effects of microbiota immaturity in undernourished
children.
Furthermore, researchers postulate that
understanding the interrelationships between
microbiota and brain metabolism in childhood
undernutrition could provide insights about
responses to injury seen in adults. They discuss
approaches that can be used to test these
hypotheses, their ramifications for optimizing
nutritional recommendations that promote healthy
brain development and function, and the potential
societal implications of this area of investigation.
In a previous study UCLA researchers have the first
evidence that bacteria ingested in food can affect
brain function in humans. In an early
proof-of-concept study of healthy women, they found
that women who regularly consumed beneficial
bacteria known as probiotics through yogurt showed
altered brain function, both while in a resting
state and in response to an emotion-recognition
task.
The study, conducted by scientists with the Gail and
Gerald Oppenheimer Family Center for Neurobiology of
Stress, part of the UCLA Division of Digestive
Diseases, and the Ahmanson–Lovelace Brain Mapping
Center at UCLA, appears in the online edition of the
peer-reviewed journal Gastroenterology.
The small study involved 36 women between the ages
of 18 and 55. Researchers divided the women into
three groups: one group ate a specific yogurt
containing a mix of several probiotics — bacteria
thought to have a positive effect on the intestines
— twice a day for four weeks; another group consumed
a dairy product that looked and tasted like the
yogurt but contained no probiotics; and a third
group ate no product at all.
Functional magnetic resonance imaging (fMRI) scans
conducted both before and after the four-week study
period looked at the women's brains in a state of
rest and in response to an emotion-recognition task
in which they viewed a series of pictures of people
with angry or frightened faces and matched them to
other faces showing the same emotions.
The researchers found that, compared with the women
who didn't consume the probiotic yogurt, those who
did showed a decrease in activity in both the insula
— which processes and integrates internal body
sensations, like those from the gut — and the
somatosensory cortex during the emotional reactivity
task.
Further, in response to the task, these women had a
decrease in the engagement of a widespread network
in the brain that includes emotion-, cognition- and
sensory-related areas. The women in the other two
groups showed a stable or increased activity in this
network.
During the resting brain scan, the women consuming
probiotics showed greater connectivity between a key
brainstem region known as the periaqueductal grey
and cognition-associated areas of the prefrontal
cortex. The women who ate no product at all, on the
other hand, showed greater connectivity of the
periaqueductal grey to emotion- and
sensation-related regions, while the group consuming
the non-probiotic dairy product showed results in
between.
The researchers were surprised to find that the
brain effects could be seen in many areas, including
those involved in sensory processing and not merely
those associated with emotion, Tillisch said.
For more information
Feeding the brain and nurturing the mind: Linking
nutrition and the gut microbiota to brain
development
PNAS 2015 112 (46) 14105-14112
Link...
Changing gut bacteria through diet affects brain
function, UCLA study shows
UCLA - University of California at Los Angeles
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