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January/February 2018^ DISCOVER^67

TOP: MINGMING LI ET AL./NATURE COMMUNICATIONS 8, ARTICLE NUMBER: 177 (2017) CC BY 4.0. BOTTOM: MEDICAL WRITERS/SCIENCE SOURCE

❯

A COUPLE OF DECADES AGO,

seismologists noticed some strange

behavior below Earth’s surface. Seismic

waves that normally pass through the planet’s

inner layers with ease got caught up in the rocky

lower mantle, roughly halfway to Earth’s center.

The waves slowed down by as much as 30 percent.

Scientists surmised the ripples had hit partially

molten pockets and dubbed the areas ultra-low

velocity zones (ULVZs).

In August, geologists reported in Nature

Communications that they overlaid ULVZ locations

with computer models of the heat flow through

the mantle and spotted something interesting. The

pockets aren’t situated in places hot enough to melt

the lower mantle’s rock. Therefore, they must be

made of minerals with a lower melting point, says

Arizona State University geophysicist Mingming Li,

the study’s lead author. Although the regions’ precise

composition remains unknown, their geological

distinctiveness suggests mantle materials never fully

mixed, even over billions of years. “Deciphering this

mystery undoubtedly holds a key to understanding

the evolution of our planet,” Li says. — JONATHON KEATS

❯

TODAY’S PAINKILLERS

target the brain and

spinal cord. But in April,

neuroscientists reported that there

might be a way to block pain before

it makes it to those central systems.

An international team of

researchers found that peripheral

nerves play an unexpected role in

processing pain.

Experts had thought these cells

merely relayed information to the

spinal cord, which integrates other

incoming pain signals and sends

them to the brain for interpretation.

During this process, both the

brain and spinal cord use chemical

messengers, or neurotransmitters,

to turn pain up or down. Scientists

believed this ability was limited to

the brain and spinal cord.

But the team noticed that in

rodents, neurons near the spine used

a neurotransmitter called gamma-

aminobutyric acid (GABA) to dial

back pain signals before sending

them on. When the researchers

administered GABA to those neurons

in rats, the animals hardly reacted to

a painful injection into their paws.

The finding, published in the

Journal of Clinical Investigation,

might radically change how we

treat pain, assuming it holds

up for humans, too, says senior

author Nikita Gamper. Painkillers

that act on peripheral nerves, he

says, would have far fewer side

effects and shouldn’t be addictive.

— JESSICA MCDONALD

A Better Way to Control Pain?

Earth’s Hot

Pockets

Ultra-low velocity zones (ULVZs), shown in red, are pockets

of molten rock roughly halfway to Earth’s center. Seismic

waves slow down by as much as 30 percent when passing

through them.

Painkillers could

one day target

our peripheral

nervous system

(purple) instead

of our central

nervous system

(red) thanks

to one cell

type’s newly

discovered

role in pain.