BODY & BRAIN
it has a social side
The brain structure does more
than coordinate movement
BY LAURA SANDERS
Its name means “little brain” in Latin,
but the cerebellum is anything but. The
fist-sized orb at the back of the brain has
an outsize role in social interactions, a
study in mice suggests.
Once thought to be a relatively simple
brain structure that had only one job,
coordinating movement, the cerebellum
is gaining recognition for being an important mover and shaker in the brain.
The “cerebellum has more than half of
the neurons in your entire brain,” says
neuroscientist Kamran Khodakhah of
Albert Einstein College of Medicine in
New York City. “It never made sense that
the only thing it confines itself to do is
Khodakhah’s results on social behavior,
described in the Jan. 18 Science, expand
that view. And by finding a connection
between the cerebellum and a part of
the brain involved in social behavior, he
and his colleagues “solve an important
gap in our understanding of the circuitry
underlying disorders such as autism and
schizophrenia,” says pediatric neurolo-
gist Mustafa Sahin of Boston Children’s
Hospital. “We’ve known for a while that
the cerebellum is involved in these dis-
orders, but we really haven’t been able to
connect it to other regions directly.”
Khodakhah’s group went looking for
connections to one such region — the
ventral tegmental area, or VTA, which
is heavily involved in feeling the thrill of
reward. Using molecular tools that light
up certain cells with fluorescent proteins,
the team saw that some of the cerebel-
lum’s nerve cells, or neurons, connect
directly to cells in the VTA in mice.
And those connections are impor-
tant. The team used a method called
optogenetics to control the cerebellar
neurons that send messages to the
VTA. The mice seemed to like when the
neurons were activated, spending more
time in a part of a square chamber where
cells were turned on.
The cells, which were also active when
mice were in contact with a compan-
ion, seem to send a feel-good signal that
comes from social interactions. When
the team turned the cells off with lasers,
mice no longer preferred to hang out with
a fellow mouse instead of an empty room.
That social deficit suggests that this par-
ticular neural highway is involved in
social behavior, Khodakhah says.
Tying the cerebellum to social behav-
ior might explain connections to autism.
Damage to the cerebellum ups the risk of
autism, which comes with social deficits.
Sahin has found some deficits in the cere-
bellar cells of people with a certain form
of autism. The newfound neural high-
way “adds to our understanding of the
circuitry of social behavior and reward
behavior in a very important way,” he says.
The cerebellum has other jobs, too,
says neurologist Jeremy Schmahmann
of Massachusetts General Hospital in
Boston. People with damage to the cere-
bellum can have trouble with memory,
planning, multitasking, creativity and
language. That constellation of symp-
toms shows that the cerebellum has
wide-ranging jobs, Schmahmann says.
An example comes from experiments with people reported in 2018 in
NeuroImage. When scientists temporarily interfered with the cerebellum using
strong magnets, people grew worse at
seeing emotions on other people’s faces.
Those results add to the growing real-ization that the cerebellum might have
its hands in many aspects of the brain.
These expanded roles for the cerebellum are “not unexpected, but almost
required,” Schmahmann says. s
LIFE & EVOLU TION
Plucky young penguins navigate the high seas
Only months after their first ocean swim, young emperor penguins brave
Antarctica’s dangerous winter seas. GPS trackers attached to 15 young penguins
revealed the birds go north to warmer waters beyond Antarctic pack ice in the
Southern Hemisphere’s summer, returning a few months later as the waters chill.
Some scientists had thought inexperienced juveniles (like those shown above)
would stick to the sea ice’s edge rather than risk freezing in the ice-strewn sea.
But 5-month-old emperor penguins were already diving to depths of about 100
meters, as adults do, Sara Labrousse and colleagues report in the Jan. 17 Marine
Ecology Progress Series. These birds also headed more than 1,000 kilometers
north to open, ice-free waters. There, the youngsters made mostly shallow
dives, probably hunting fish and krill that feast on floating algae, the authors say.
After a few months, the fattened youngsters returned to the sea ice for winter.
Why the birds return to Antarctica in winter is unclear. Perhaps they go to
feed on krill that eat the algae growing on the ice, says Labrousse, of Woods
Hole Oceanographic Institution in Massachusetts. — Jeremy Rehm