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52
53
January/February 2018^ DISCOVER^57
TOP: GEORGE POINAR JR./OREGON STATE UNIVERSITY (2). BOTTOM: LIGHTSPRING/SHUTTERSTOCK
Amber Preserves Tick’s Last Supper
❯
AN AMBER-TRAPPED TICK found in
the Dominican Republic contains
the oldest mammalian red blood
cells ever discovered. According to a study
in the Journal of Medical Entomology
in March, a grooming primate likely
punctured the tick’s shell — releasing blood
and betraying its presence to scientists
millions of years later — and then flicked
the critter into tree sap, where it was
preserved for some 15 million to 45 million
years. The cells contain a parasite related
to a modern species commonly carried
by ticks, shedding light on the entwined
history of our ancestors and the organisms
that preyed on them. — NATHANIEL SCHARPING
A Quick Start to Long-Lasting Memories
❯
NEUROSCIENTISTS
THOUGHT long-term
memories took weeks
to form. But MIT researchers have
discovered those
memories can take
hold in the brain
much sooner.
The team used
a technique called
optogenetics, in
which light-responsive
proteins are
genetically inserted
into brain cells,
allowing researchers
to activate them with
lasers to find out
what they do. The
group trained mice
with these engineered
neurons to fear an
electric shock and,
with a blast of laser
light, could spot
the brain cells involved in that
painful memory.
The team identified memory
cells in the neocortex — the brain’s
outer layers, which house long-
term memories — within just a day
of the shock. When the scientists
stimulated those cells with light,
the critters cowered in
fear, showing that the
long-term memories
were already there.
Along with
furthering our
understanding of
memory, the results,
published in April in
Science, also may help
explain what happens
during dementia.
“We are nothing
but memory,” says
senior author Susumu
Tonegawa. “So we
want to understand
how it works, and we
want to understand
why it goes wrong.”
— JESSICA MCDONALD
Close-up of fossilized
blood cells.