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| Dec 10, 2005 11:07 pm |
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How the "trust hormone" works |
Bala Pillai
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How the “trust hormone” works
http://www.world-science.net/othernews/051208_trustfrm.htm
Dec. 8, 2005
Courtesy NIH/National Institute of Mental Health
and World Science staff
A brain chemical that boosts trust seems to work by reducing activity and damping connections in brain circuits that process fear, a study has found.
The chemical, oxytocin, is a natural brain hormone thought to be linked to bonding, social attachment and, some scientists believe, love. It is also the key ingredient in a “trust potion” that researchers developed recently: when people sniffed it, they temporarily became more trusting.
In the new study, researchers said they showed through brain scans that oxytocin quells the brain’s fear center and associated “relay stations” in response to frightening images.
The work suggests new approaches to treating conditions involving excessive fear in social situations, the scientists added. These conditions include social phobia, autism, and possibly schizophrenia.
The research suggests chemicals similar to oxytocin could serve as therapies in these disorders, added Thomas Insel, director of the National Institute of Mental Health in Bethesda, Md., where the study was conducted.
The study, by the institute’s Andreas Meyer-Lindenberg and colleagues, appears in the December 7 issue of the Journal of Neuroscience.
Animal studies “have shown that oxytocin plays a key role in complex emotional and social behaviors, such as attachment, social recognition and aggression,” said Elias Zerhouni, director of the National Institutes of Health, the U.S. agency of which the National Institute of Mental Health is a part. “Now, for the first time, we can literally see these same mechanisms at work in the human brain.”
The researchers started their study as a result of the “trust potion” study reported last June by Swiss researchers. Also, previous research had linked trusting behavior to decreased activity in a brain area called the amygdala.
Meyer-Lindenberg hypothesized that oxytocin boosts trust by suppressing the amygdala and its fear-processing networks.
To test this idea, he asked 15 healthy men to sniff either oxytocin or a neutral control substance before receiving a brain scan with a technology called functional magnetic resonance imaging. The scans show which parts of the brain are stimulated by specific activities.
While in the scanner, the men looked at angry or fearful faces and threatening scenes, activities known to stimulate the amygdala.
As expected, the threatening pictures triggered strong amygdala activation during the scans without oxytocin, but markedly less activity with oxytocin, the researchers reported. The difference was especially pronounced in response to threatening faces, they added, suggesting a key role for oxytocin in regulating social fear.
Moreover, they found oxytocin dampened the amygdala’s communication with other brain centers thought to “telegraph” fear throughout the brain. These sites are in the brain stem, a primitive part of the brain connected to the spinal cord.
The results mirrored findings in rats, reported earlier this year by European scientists, the researchers added.
“This dual mode of action of oxytocin in humans suggests a potentially powerful treatment approach toward socially relevant fear,” wrote the scientists. This is because increased amygdala activation has been associated with social phobia, genetic risk for anxiety and depression, and possibly with social fear in autism.
Autistic people tend to avoid looking at faces, and doing so seems to stimulate their amygdalas, the researchers added. Meyer-Lindenberg said future studies may thus test oxytocin as a treatment for such social anxiety symptoms in autistic children.
Future research may also examine how oxytocin affects the amygdala in women, and the function of related hormones, such as a chemical called vasopressin, Meyer-Lindenberg said. Another subject of scrutiny, he added, will be how genetic variants in these hormones affect brain function.
cheers../bala
Bala Pillai bala@apic.net
Sydney, Australia
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