Impulsive? Blame Brain's Instant
Gratification Hot Spot
http://www.msnbc.com/news/./577804.asp?0na=223R3h0-
5-24-1
Trying to choose between a cookie or a
carrot at snack
time? A newly identified "hot
spot" on the brain may be
the key to impulsive behavior, involved in
the critical
choice between instant gratification and
delayed
reward, researchers said Thursday.
In a study reported in the journal
Science, researchers
examined the nucleus accumbens, located at
the base of
the forebrain. The region responds to
natural rewards
such as food and sex, as well as drugs
such as
amphetamines and cocaine, through their
effects on the
neurotransmitter chemical dopamine.
"We have shown that damage or
dysfunction of the
nucleus accumbens can cause, without a
doubt, impulsive
choice," said study author Rudolf
Cardinal, of the
Department of Experimental Psychology in
Britain's
University of Cambridge.
The findings have implications for the
treatment and
understanding of drug addiction,
attention
deficit/hyperactivity disorder (ADHD) and
anti-social
behavior, all of which are linked to the
impulse for
instant gratification.
The researchers trained rats to choose
between a small
immediate reward and a larger, delayed
reward. In tests
after their nucleus accumbens were
damaged, the
researchers found the rats tended to
choose the instant
gratification of the small reward, rather
than the
larger reward delivered after a
delay.
"We already knew that there was a
correlation between
abnormalities in the nucleus accumbens and
impulsive
behavior," Cardinal said. "Now
we have clear evidence
that such abnormalities can cause this
behavior."
Lesions on two other regions of the brain
that send
information to the nucleus accumbens, the
anterior
ingulate cortex and medial prefrontal
cortex, did not
cause the rats to act impulsively, the
study found.
The findings "suggest the nucleus
accumbens core, at
least for impulsive choice, is a
criticalregion,"
Cardinal said.
The research also sheds new light on drugs
like
Ritalin, used to treat ADHD by affecting
the dopamine
systems in the brain.
"Our research suggests that
(Ritalin's) actions in the
nucleus accumbens may responsible for its
beneficial
affects on impulsive behavior," he
said.
A SMOKER'S CHOICE
Like most discoveries, the study has
triggered more
questions.
"I think it's an interesting question
to ask, why were
the animals with nucleus accumbens lesions
impulsive?"
Cardinal said. "Were they impulsive
because they were
less sure that in fact, delayed reward was
coming?"
The cigarette smoker's choice is a good
analogy, he
said, and further research is needed to
determine what
is going on, he said.
The choice is cigarettes now or avoiding
lung cancer
later, he said. So does the smoker really
believe that
cigarettes cause lung cancer? Or maybe the
smoker
believes cigarettes cause cancer but cares
less about
long-term health than the instant
buzz.
"That's one question about the
underlying psychology,"
Cardinal said. "Do you make your
impulsive choices in
the full knowledge of what you are getting
yourself
into? Or do you lack insight into the
consequences?"
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Mike Lee,
MA [EMAIL PROTECTED]
Dept of
Psychology http://home.cc.umanitoba.ca/~mdlee
University of Manitoba
Winnipeg, MB Canada
"Our situation on this Earth seems strange.
Every one of us appears here involuntarily,
and uninvited, for a short stay without knowing why. To me it is
enough to wonder at the secrets."
-- Albert Einstein
"Men are probably nearer the central truth in their
superstitions than in
their science." --Henry David Thoreau