always been a psychological explana-
tion for that ... but what if that
somehow is the survival of the
bacterial fittest?”
This is one of several theories
about how the microbiome might
contribute to eating disorders. There
are also ideas about how microbes
might influence inflammation, accord-
ing to Beate Herpertz-Dahlmann, a
child and adolescent psychiatrist at
the RWTH University Clinics in
Germany who is currently involved in
projects that are investigating this link
in several European countries.
Bacteria, for instance, may develop
antibodies against molecules that
influence appetite. Another possibility
is that a deeply altered microbiome
could lead to a so-called leaky gut, in
which pathological material seeps
through the intestines into the blood
vessels, evoking an immune response
elsewhere in the body, in areas such
as the brain.
“[Eating disorders] were first
described in the 1600s, and it’s
amazing how little we know about
how to manage and treat them,” Gold-
en says. “A better understanding of
how these diseases develop will
advance us in our treatments.”
—Diana Kwon
The Adult Brain Does
Grow New Neurons
After All, Study Says
Study points toward lifelong neu-
ron formation in the human brain’s
hippocampus, with implications for
memory and diseaseIF THE MEMORY center of the human
brain can grow new cells, it might
help people recover from depression
and post-traumatic stress disorder
(PTSD), delay the onset of Alzhei-
mer’s, deepen our understanding of
epilepsy and offer new insights into
memory and learning. If not, well then,
it’s just one other way people are
different from rodents and birds.
For decades, scientists have
debated whether the birth of new
neurons—called neurogenesis—was
possible in an area of the brain that is
responsible for learning, memory and
mood regulation. A growing body of
research suggested they could, but
then a Nature paper last year raised
doubts.
Now, a new study published in
March in another of the Nature family
of journals—Nature Medicine—tips thebalance back toward “yes.” In light of
the new study, “I would say that there
is an overwhelming case for the
neurogenesis throughout life in
humans,” Jonas Frisén, a professor at
the Karolinska Institute in Sweden,
said in an e-mail. Frisén, who was not
involved in the new research, wrote a
News and Views about the study in
the March issue of Nature Medicine.
Not everyone was convinced.
Arturo Alvarez-Buylla was the senior
author on last year’s Nature paper,
which questioned the existence of
neurogenesis. Alvarez-Buylla, a
professor of neurological surgery at
the University of California, SanFrancisco, says he still doubts that
new neurons develop in the brain’s
hippocampus after toddlerhood.
“I don’t think this at all settles things
out,” he says. “I’ve been studying adult
neurogenesis all my life. I wish I could
find a place [in humans] where it
does happen convincingly.”
For decades, some researchers
have thought that the brain circuits of
primates—including humans—would
be too disrupted by the growth of
substantial numbers of new neurons.
Alvarez-Buylla says he thinks the
scientific debate over the existence
of neurogenesis should continue.
“Basic knowledge is fundamental. GETTY IMAGESNEWS
Cerebral cortical neuron.