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Amygdala gone, she knows no fear
By Laura Sanders
A middle-aged woman
known as SM blithely
reaches for dangerous
snakes, giggles in haunted
houses and once, upon
escaping the clutches of a
knife-wielding man, didn’t
run but calmly walked away.
A rare kind of brain damage
precludes her from feeling
fear of any sort, finds a study published
online December 16 in Current Biology.
SM has an unusual genetic disorder
called Urbach-Wiethe disease. In late
childhood, this disease destroyed both
sides of her amygdala, which is composed
of two structures the shape and size of
almonds, one on each side of the brain.
Animal experiments have strongly
implicated the amygdala in fear processing. “But one thing we’ve never known for
sure, because they’re animals, is whether
they can consciously feel fear,” says study
coauthor Justin Feinstein of the Univer-
A rare genetic disease destroyed a middle-aged
woman’s amygdala (red), making her immune to
fear even in the most traumatic circumstances.
sity of Iowa in Iowa City. “So we said, ‘Let’s
take a human patient who has this same
sort of damage, and for the first time, actu-
ally figure out how they’re feeling.’”
SM told Feinstein and his colleagues
that she never felt fear, even when threat-
ened with a knife or a gun. The research-
ers gave her an electronic diary that she
carried for three months to record her
emotional state. Fear didn’t appear once.
On a battery of questionnaires, SM wrote
that she wasn’t afraid of public speaking,
death, her heart beating too fast or being
judged negatively in a social setting.
The researchers showed SM clips from
scary movies: She was interested, but not
afraid. They took her to a haunted house.
Instead of screaming, she laughed and
poked one of the monsters in the head.
SM claimed to dislike snakes and spiders. But during a visit to an exotic pet
store she was overcome with curiosity,
repeatedly asking to touch the snakes.
“Perhaps the amygdala is acting at a
very instinctual, unconscious level,” says
Feinstein. “Without this area, instead of
just losing your interest in things, you do
the very thing that’s opposite. She tends
to approach the very things she should
be avoiding.”
A study of one person can’t be extended
to everyone, says neuroscientist Hans
Markowitsch of the University of Biele-
feld in Germany. And pinning a complex
emotional state to a single brain struc-
ture isn’t straightforward. “One could
argue that the amygdala cannot act on its
own — it’s dependent on connections, on
circuits, on other brain regions,” he says.
The study’s authors can’t dismiss
other brain regions’ roles in fear. Yet
SM’s complete inability to experience
the emotion, in a wide variety of forms,
highlights the amygdala’s pivotal role. s
Blood test can
spot heart risk
cardiac troponin T could be
added to existing indicators
By Nathan Seppa
A new blood test might reveal heart damage that puts some people at a hidden
higher risk of cardiac failure or death,
researchers report in the Dec. 8 Journal
of the American Medical Association.
Although factors such as obesity, diabetes or high blood pressure hike heart
disease risk, many people without these
problems have heart attacks. Efforts to
identify other warning signs have focused
largely on two compounds, C-reactive
protein and B-type natriuretic peptide.
But only blood levels of BNP have shown
predictive ability (SN: 1/7/06, p. 13).
Two new studies suggest that a blood
compound called cardiac troponin T
might outperform both as a risk indicator.
In one analysis, Christopher deFilippi
of the University of Maryland School of
Medicine in Baltimore and his colleagues
sampled blood from more than 5,000
people nationwide who were 65 or older
and had no history of heart failure. During
nearly 12 years of follow-up, on average,
people with the highest levels of cardiac
troponin T at the study outset were at
least 51 percent more likely to develop
heart failure and 70 percent more apt to
die from cardiovascular causes than those
with the lowest levels. The researchers
accounted for factors such as blood pres-
sure, previous heart disease and smoking.
