Scientific American - USA (2022-02)

ADVANCES

18 Scientific American, February 2022

INDIA

Geologists found

groups of rocks in India

to be about 3.2 billion

years old. The rocks

consisted of sediments

eroded from land,

which suggests that

large landmasses

emerged from the sea

more than half a billion

years earlier than many

researchers believed.

GERMANY

Silver-studded blue butterflies naturally favor grassland

habitats, but researchers recently found four times as

many in active mining quarries than in similar-sized

meadows. The insects lay their eggs on certain plants,

which mining operations may help thrive by eliminating

larger, competing vegetation.

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RUSSIA

While analyzing DNA found in Siberian sediments,

scientists discovered that mammoths survived there until

around 4,000 years ago—much later than previously

thought. This finding means humans may have coexisted

with the beasts for thousands of years without over-

hunting them.

COSTA RICA
Scientists found that meat-
eating “vulture bees” have
evolved more acidic guts
that harbor acid-tolerant
bacteria, similar to those
found in vultures and
hyenas, letting the insects
safely consume carrion.

ZIMBABWE

Investigators recently determined the age of one of Africa’s most

famous trees, a 25-meter-tall baobab named “Big Tree.” Because

baobabs do not form regular tree rings, scientists analyzed Big

Tree’s carbon decay to determine it was an impressive 1,150 years old.

IN THE NEWS

Quick

Hits

By Nikk Ogasa

BRAZIL
Measurements over the past 40 years
revealed that 77 Amazonian bird
species lost 0.1 to 2 percent of their
average weight each decade.
Researchers suggest the birds may
have adapted leaner shapes to cope
with climate warming; 61 species also
developed longer, more efficient wings.

NEUROSCIENCE

Sated Brain

A surprising brain area

helps to curb overeating

People with a rare genetic disorder
known as Prader-Willi syndrome never feel
full, and this insatiable hunger can lead to
life-threatening obesity. Scientists studying
the problem have now found that the fist-
shaped structure known as the cerebel-
lum—which had not previously been
linked to hunger —is key to regulating sati-
ation in those with this condition.
This finding is the latest in a series of dis-
coveries revealing that the cerebellum, long
thought to be primarily involved in motor
coordination, also plays a broad role in cog-
nition, emotion and behavior. “We’ve
opened up a whole field of cerebellar control
of food intake,” says Albert Chen, a neurosci-
entist at the Scintillon Institute in California.
The project began with a serendipitous
observation: Chen and his team noticed
they could make mice stop eating by acti-
vating small pockets of neurons in regions

known as the anterior deep cerebellar

nuclei (aDCN), within the cerebellum.

Intrigued, the researchers contacted col-

laborators at Harvard Medical School. Sci-

entists there had gathered data using func-

tional MRI to compare brain activity in 14

people who had Prader-Willi syndrome

with activity in 14 unaffected people while

each subject viewed images of food—

either immediately following a meal or

after fasting for at least four hours.

New analysis of these scans revealed

that activity in the same regions Chen’s

group had pinpointed in mice, the aDCN,

appeared to be significantly disrupted in

humans with Prader-Willi syndrome. In

healthy individuals, the aDCN were more

active in response to food images while

fasting than just after a meal, but no such

difference was identifiable in participants

with the disorder. The result suggested

that the aDCN were involved in controlling

hunger. Further experiments on mice, con-

ducted by researchers from several differ-

ent institutions, demonstrated that activat-

ing the animals’ aDCN neurons dramati-

cally reduced food intake by blunting how

the brain’s pleasure center responds

to food. The findings were recently

detailed in Nature.

For years neuroscientists studying

appetite focused mainly either on the

hypothalamus, a brain area involved in reg-

ulating energy balance, or on reward-pro-

cessing centers such as the nucleus accum-

bens. But this group has identified a novel

feeding center in the brain, says Elanor Hin-

ton, a neuroscientist at the University of

Bristol in England who was not involved

with the study. “I’ve been working in appe-

tite research for the past 15 years or so, and

the cerebellum has just not been a target,”

Hinton says. “I think this is going to be

important both for Prader-Willi syndrome

and, much more widely, to address obesity

in the general population.”

Multiple colleagues of Chen’s are now

planning to test whether they can manipu-

late this circuit in healthy people by using

a noninvasive intervention known as tran-

scranial magnetic stimulation. If that is

successful, Chen says, the researchers

hope to eventually conduct a clinical trial.

— Diana Kwon