Body & Brain
He’s not a rat,
he’s my brother
Rodents exhibit empathy by
setting trapped friends free
By Laura Sanders
Calling someone a rat should no longer be
considered an insult. The often maligned
rodents go out of their way to liberate a
trapped friend, proactive behavior that’s
driven by empathy, researchers conclude
in the Dec. 9 Science.
“As humans, we tend sometimes to
have this feeling that there’s some-
thing special about our morals,” says
neuroscientist Christian Keysers at the
Netherlands Institute for Neuroscience
in Amsterdam, who was not involved in
the study. “It seems that even rats have
this urge to help.”
As many pet rat owners know, rats are
highly social animals, says study coauthor
Inbal Ben-Ami Bartal, a psychologist at
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the University of Chicago. Bartal and
colleagues wanted to see whether rats
would take action to ease the suffering of
a cage mate. The team put one rat inside
a clear cage that could be sprung from the
outside and left another rat to roam free
outside the cage for an hour at a time.
Initially, the free rat would circle the
cage, digging and biting at it. After about
seven days of encountering its trapped
friend, the roaming rat learned how to
open the cage and liberate the captive.
“It’s very obvious that it is intentional,”
Bartal says. “They walk right up to the
door and open the door.” The liberation
is followed by a frenzy of excited running.
The rats would selectively take action
when another rat was in distress: Empty
cages didn’t inspire rats to learn how to
open the door nearly as well as those who
were motivated to rescue a trapped rat. By
the end of the experiment, only five of 40
rats learned to open an empty cage, while
23 of 30 rats learned to open the cage to
free an occupant. (Trapped stuffed animals fared no better than empty cages.)
“If I open the door, that rat’s distress
goes away and my distress goes away,”
says psychologist Matthew Campbell of
Yerkes National Primate Research Cen-
ter at Emory University in Atlanta, who
studies empathy in chimpanzees. “They
are affected by what the other is experi-
encing, and that alone is remarkable.”
To push the limits of the rats’ good-
will, Bartal’s team pitted a trapped rat
against trapped chocolate, forcing a rat
to choose which to release first. “These
rats adore their chocolate,” she says. The
rats were equally likely to free a rat in
distress as they were to free the sweets.
To a rat, a friend’s freedom was just as
sweet as five chocolate chips.
“The most shocking thing is they left
some of the chocolate for the other rat,”
Bartal says. The hero rat left a chocolate
chip or two for its newly free associate in
more than half of the trials. On purpose.
“It’s not like they missed a chocolate,”
Bartal says. “They actually carried it out
of the restrainer sometimes but did not
eat it.” s
Coffee delivers jolt deep in brain
Caffeine strengthens electrical signals in rats’ hippocampus
By Laura Sanders
Most coffee addicts would tell you that
caffeine sharpens the mind. It turns
out that in rodents, a single dose of caffeine does indeed strengthen cell connections in an underappreciated part
of the brain, scientists report online
November 20 in Nature Neuroscience.
A clearer idea of caffeine’s effect on the
brain could allow scientists to
take advantage of its stimulating effects and perhaps even
alleviate some brain disorders.
So far, most of caffeine’s
effects have been studied at
doses much higher than in an
average cup, says study coauthor
Serena Dudek of the National
Institute of Environmental Health Sciences in Research Triangle Park, N. C.
Her team tested smaller hits of caffeine on a part of the hippocampus. In
humans, this seahorse-shaped structure
is buried deep in the brain behind the
ears. After feeding rats a caffeine dose
equivalent to two human cups of coffee
(two milligrams of caffeine per kilogram
of body weight), the team measured
the strength of nerve cells’
electrical messages in slices
of brain tissue. Nerve cells
in this particular
nook — a region called
CA2 — showed a bigger burst of electrical
activity when researchers
stimulated the cells. Nerve
of body weight), the team measured the strength of nerve cells’ electricalmessages inslices of brain tissue. Nerve cells in this particular nook—aregioncalled CA2—showed a big- ger burst of electrical activity when researcherstimulated timulated the cells. Nerve
cells in a nearby part of the hippocampus
didn’t show this sensitivity.
And the higher the caffeine dose, the
stronger the effect. A caffeine dose 10
times higher — a dose reached by only
die-hard caffeine consumers — caused an
even bigger response in CA2 nerve cells.
Similar effects occurred when applying caffeine directly to CA2 nerve cells in
a dish, ruling out post-caffeine changes
in blood flow as the cause. After five minutes of caffeine exposure, the cells stayed
amped up for three hours.
These strengthened cell connections
may have a role in learning and memory,
as a main job of the hippocampus is to
form spatial memories. But it’s unclear
how the research will apply to people.
“It’s hard to jump from these kinds of
studies to direct application to humans,”
says psychologist Harris Lieberman of the
U.S. Army Research Institute of Environmental Medicine in Natick, Mass.
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