Navigation Links
Scientists uncover new clues about brain function in human behavior

Researchers at the National Institute of Mental Health (NIMH), part of the National Institutes of Health, have discovered a genetically controlled brain mechanism responsible for social behavior in humans--one of the most important but least understood aspects of human nature. The findings are reported in Nature Neuroscience, published online on July 10, 2005.

The study compared the brains of healthy volunteers to those with a genetic abnormality, Williams Syndrome, a rare disorder that causes unique changes in social behavior. This comparison enabled the researchers to both define a brain circuit for social function in the healthy human brain, and identify the specific way in which it was affected by genetic changes in Williams Syndrome.

People with Williams Syndrome who are missing about 21 genes on chromosome seven are highly social and empathetic, even in situations that would elicit fear and anxiety in healthy people. They will eagerly, and often impulsively, engage in social interactions, even with strangers. However, they experience increased anxiety that is non-social, such as fear of spiders or heights (phobias) and worry excessively.

For several years, scientists have suspected that abnormal processing in the amygdala, an almond-shaped structure deep in the brain, may be involved in this striking pattern of behavior. The amygdala's response and regulation are thought to be critical to people's social behavior through the monitoring of daily life events such as danger signals. Scientists know from animal studies that damage to the amygdala impairs social functioning.

"Social interactions are central to human experience and well-being, and are adversely affected in psychiatric illness. This may be the first study to identify functional disturbances in a brain pathway associated with abnormal social behavior caused by a genetic disorder," said NIMH Director Thomas R. Insel, M.D.

In this study, investigators used function al brain imaging (fMRI) to study the amygdala and structures linked to it in 13 participants with Williams Syndrome who were selected to have normal intelligence (Williams Syndrome is usually associated with some degree of mental retardation or learning impairment) and compared to healthy controls. Andreas Meyer-Lindenberg, M.D., Ph.D., and Karen Berman, M.D., from the NIMH Genes, Cognition, and Psychosis Program, and colleagues, then showed participants pictures of angry or fearful faces. Such faces are known to be highly socially relevant danger signals that strongly activate the amygdala. The fMRI showed considerably less activation of the amygdala in participants with Williams Syndrome than in the healthy volunteers (see graphic below). These findings suggest that reduced danger signaling by the amygdala in response to social stimuli might be responsible for their fearlessness in social interactions.

Next, researchers showed the study participants pictures of threatening scenes (a burning building or a plane crash), which did not have any people or faces in them and thus had no immediate social component. In remarkable contrast to the response to faces, the amygdala response to threatening scenes was abnormally increased in participants with Williams Syndrome (see graphic below), mirroring their severe non-social anxiety.

"The amygdala response perfectly reflected the unique profile of social and non-social anxiety in Williams Syndrome," said Meyer-Lindenberg. "Because our data showed that the amygdala did still function, although abnormally, in Williams Syndrome, we wondered whether it might be its regulation by other brain regions that was the cause of the amygdala abnormalities."

To investigate this, the scientists looked at the whole brain to identify other regions where reactivity was different between Williams's participants and healthy volunteers. They identified three areas of the prefrontal cortex, located in the front part of th e brain, that have been implicated in decision-making, representation of social knowledge, and judgment. Those regions are the dorsolateral, the medial, and the orbitofrontal cortex. Specifically, the dorsolateral area is thought to establish and maintain social goals governing an interaction; the medial area has been associated with empathy and regulation of negative emotion; and orbitofrontal region is involved in assigning emotional values to a situation.

The researchers found a delicate network by which these three regions modulate amygdala activity. In Williams Syndrome, this fragile system was significantly abnormal, particularly the orbitofrontal cortex. This area did not activate for either task and was not functionally linked to the amygdala, as it was in healthy controls. Instead, the scientists observed increased activity and linkage in the medial region, which is consistent with the high level of empathy exhibited by people with Williams Syndrome.

"We had previously seen that the orbitofrontal cortex is structurally abnormal in Williams Syndrome, but we didn't know what role it played functionally in the disorder; it is now clear that this area can play a major role in producing social behavioral abnormalities," said Berman. "The over-activity of the medial-prefrontal cortex may be compensatory, but the result is still an abnormal fear response. The medial-prefrontal cortex still works and in fact it is working over-time because it may be the only thing that still regulates the amygdala in Williams Syndrome."


'"/>

Source:NIH/National Institute of Mental Health


Related biology news :

1. Scientists ID molecular switch in liver that triggers harmful effects of saturated and trans fats
2. Scientists Replicate Hepatitis C Virus in Laboratory
3. Scientists detect probable genetic cause of some Parkinsons disease cases
4. Scientists find missing enzyme for tuberculosis iron scavenging pathway
5. Scientists seek answers on what activates deadly anthrax spores
6. Yale Scientists Find MicroRNA Regulates Ras Cancer Gene
7. Scientists collaborate to assess health of global environment
8. Scientists decipher genome of fungus that can cause life-threatening infections
9. Scientists discover the cellular roots of graying hair
10. Scientists rid stem cell culture of key animal cells
11. Scientists develop new color-coded test for protein folding
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:4/6/2017)... LONDON , April 6, 2017 ... Control, RFID, ANPR, Document Readers, by End-Use (Transportation & ... Energy Facility, Oil, Gas & Fossil Generation Facility, Nuclear ... Healthcare, Educational, Other) Are you looking for ... Authentication sector? ...
(Date:4/3/2017)... 3, 2017  Data captured by IsoCode, ... detected a statistically significant association between the ... treatment and objective response of cancer patients ... predict whether cancer patients will respond to ... well as to improve both pre-infusion potency testing ...
(Date:3/28/2017)... 2017 The report "Video Surveillance ... Servers, Storage Devices), Software (Video Analytics, VMS), and Service ... Forecast to 2022", published by MarketsandMarkets, the market was ... projected to reach USD 75.64 Billion by 2022, at ... base year considered for the study is 2016 and ...
Breaking Biology News(10 mins):
(Date:10/12/2017)... (PRWEB) , ... October 12, ... ... today announces publication of a United States multicenter, prospective clinical study that ... disposable, point-of-care diagnostic test capable of identifying clinically significant acute bacterial and ...
(Date:10/12/2017)... ... October 12, 2017 , ... ... launched Rosalind™, the first-ever genomics analysis platform specifically designed for life science ... in honor of pioneering researcher Rosalind Franklin, who made a major contribution ...
(Date:10/11/2017)... ... ... eye wash is a basic first aid supply for any work environment, but most personal ... rinse first if a dangerous substance enters both eyes? It’s one less decision, and likely ... dual eye piece. , “Whether its dirt and debris, or an acid or alkali, getting ...
(Date:10/11/2017)... 11, 2017  VMS BioMarketing, a leading provider of patient ... Clinical Nurse Educator (CNE) network, which will launch this week. ... among health care professionals to enhance the patient care experience ... and other health care professionals to help women who have ... ...
Breaking Biology Technology: