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Placebo effect
« on: 2004-05-20 21:01:21 » |
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Placebos effect revealed in calmed brain cells
New Scientist, May 16, 2004
http://www.newscientist.com/news/news.jsp?id=ns99994996
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When the patients in the study received a simple salt solution, their neurons responded in just the same way as when they had earlier received a drug which eased their symptoms.
"The research provides further evidence for a physiological underpinning for the placebo effect," says Jon Stoessl, at the University of British Columbia in Vancouver, Canada. His team demonstrated in 2001 that placebos can relieve symptoms by raising brain levels of dopamine, a beneficial neurotransmitter.
"We suggest that the changes we ourselves observed are also induced by release of dopamine," says Benedetti.
Abnormal firing
Parkinson's patients suffer from a lack of dopamine, meaning that brain cells in a region called the subthalamic nucleus firing in abnormal bursts. This triggers the familiar symptoms of muscle rigidity, tremors and slowness of movement.
Drugs which mimic dopamine, such as L-Dopa and apomorphine, can block abnormal firing. But now, Benedetti has shown that a simple saline solution did the same.
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Cognitive vs conditioning
He suggest two possible explanations. The first is the "cognitive" hypothesis, where the physiological effects are triggered by the patient's expectation of benefits.
The second is the classic "conditioning" response. This was discovered in 1889 by the Russian psychologist, Ivan Pavlov, who found conditioning could induce dogs to salivate for food at the sound of a bell. "The context around the therapy could induce such a response," says Benedetti.
In his latest experiments, Benedetti is investigating whether the brain cells react to placebos in "naive" Parkinson's patients, who have not first been conditioned with genuine drugs.
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