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Impulsive choice induced in rats by lesions of the nucleus accumbens core. Science; published online 24 May 2001 (10.1126/science.1060818).

Rudolf N. Cardinal, David R. Pennicott, C. Lakmali Sugathapala, Trevor W. Robbins, and Barry J. Everitt
Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK

News coverage of this paper seems to have spiralled beyond my ability to track it. Selected coverage is listed below. I've listed every source that interviewed me or told me that they were running the story.

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Press release from the American Association for the Advancement of Science (17 May 2001):

INSTANT GRATIFICATION ON THE BRAIN: If the choice is one cookie now or an entire cake later, can you fight the instant gratification of the cookie to wait for the delayed reward of the cake? British researchers have identified an area in the brain in rats that may be a key battleground in this tug-of-war. Inability to control instant gratification is related to drug addiction, attention-deficit disorder and hyperactivity, and some personality disorders, so scientists would like to know more about the neuroanatomical basis for this behavior. Rudolf N. Cardinal and colleagues found that lesions of the core of the nucleus accumbens caused rats to persistently make the impulsive choice when it came to food rewards. Lesions of the anterior cingulate cortex and the medial prefrontal cortex, two major areas of input to the nucleus accumbens, didn't change the choice performance of the rats.

Press release from the University of Cambridge (23 May 2001) [press release local HTML or PDF]; note also main story on 31 May 2001 [original link] [front page local HTML or PDF] [news page local HTML or PDF] [story local HTML or PDF].

I want it now!

Researchers uncover the neuroanatomy of impulsive behaviour

Is a bird in the hand worth two in the bush? The tendency to choose instant gratification rather than wait for a larger reward is linked to drug addiction, attention deficit/hyperactivity disorder (ADHD), and anti-social behaviour.

Now researchers at the University of Cambridge's Department of Experimental Psychology have discovered some of the underlying brain systems probably responsible for such impulsive behaviour.

The part of the brain implicated is a structure called the nucleus accumbens which is at the base of the forebrain. The nucleus accumbens responds to natural rewards such as food and sex, as well as drugs such as amphetamine and cocaine, through their effects on the neurotransmitter chemical dopamine.

The new research has shown that damage to the nucleus accumbens in rats results in a tendency to take small, immediate rewards, in preference to larger, but delayed rewards. Lesions to two other regions of the brain that send information to the nucleus accumbens core did not cause the rats to behave impulsively.

"We already knew that there was a correlation between abnormalities in the nucleus accumbens and impulsive behaviour," explains researcher Rudolf Cardinal. "Now we have clear evidence that such abnormalities can cause this behaviour."

The findings shed new light on the controversial drug Ritalin (or methylphenidate), generally used in the treatment of ADHD.

"Ritalin affects dopamine systems in many areas of the brain. Our research suggests that its actions in the nucleus accumbens may be responsible for its beneficial effects on impulsive behaviour," says Rudolf.

Notes for editors

1. The University of Cambridge's Department of Experimental Psychology is one of the leading British centres for research in the behavioural and cognitive sciences. The Department secured a grade of 5* in the last UK Research Assessment Exercise. Its work spans human experimental psychology, sensory and perceptual psychology, animal learning, physiological psychology, psychopharmocology and psycholinguistics.

2. The research group led by Professors Barry Everitt and Trevor Robbins investigates the neural basis of learning memory, attention, cognition, reward and reinforcement. Research into normal brain function is applied to the understanding of cognitive and behavioural disorders including drug addiction and impulsivity.

For further information please contact:
1. Rudolf Cardinal, Department of Experimental Psychology, University of Cambridge. E-mail:
2. Stuart Hogarth, Press and Publications Office, University of Cambridge. Tel: 01223 332300; e-mail:

The Press Association

Embargoed to 1900 Thursday May 24
By John von Radowitz, Science Correspondent, PA News
People who cannot resist acting on impulse may have damage to a small part of the brain involved in making choices, new research suggested today. Normally a balance is struck between giving in to instant gratification and waiting for delayed rewards. But some individuals, including drug addicts and those suffering from attention deficit hyperactivity disorder (ADHD), cannot control their urge to "have it now". British scientists found that a small neural region called the nucleus accumbens, buried deep within the brain, may hold the key to this behaviour. In laboratory experiments, trained rats with surgical lesions to the nucleus accumbens could not help acting on impulse when faced with the choice between an immediate small food reward or a more generous one later. Rather than wait for a better meal, they ate what was offered to them first. Before undergoing surgery, the rats behaved in a very different way. Until
the delay became great enough to defeat their memories, they chose to hold out for the larger reward. Rudolf Cardinal and colleagues at the University of Cambridge reported their results in the journal Science. The researchers wrote: "This finding suggests a mechanism by which Acb (nucleus accumbens) dysfunction may contribute to addiction, ADHD, and other impulse control disorders."


RADIO COVERAGE (25 May 2001)