Brain structure differs in liberals, conservatives: study

WASHINGTON (AFP) – Everyone knows that liberals and conservatives butt heads when it comes to world views, but scientists have now shown that their brains are actually built differently.

Liberals have more gray matter in a part of the brain associated with understanding complexity, while the conservative brain is bigger in the section related to processing fear, said the study on Thursday in Current Biology.

"We found that greater liberalism was associated with increased gray matter volume in the anterior cingulate cortex, whereas greater conservatism was associated with increased volume of the right amygdala," the study said.

Other research has shown greater brain activity in those areas, according to which political views a person holds, but this is the first study to show a physical difference in size in the same regions.

"Previously, some psychological traits were known to be predictive of an individual's political orientation," said Ryota Kanai of the University College London, where the research took place.

"Our study now links such personality traits with specific brain structure."

The study was based on 90 "healthy young adults" who reported their political views on a scale of one to five from very liberal to very conservative, then agreed to have their brains scanned.

People with a large amygdala are "more sensitive to disgust" and tend to "respond to threatening situations with more aggression than do liberals and are more sensitive to threatening facial expressions," the study said.

Liberals are linked to larger anterior cingulate cortexes, a region that "monitor(s) uncertainty and conflicts," it said.

"Thus, it is conceivable that individuals with a larger ACC have a higher capacity to tolerate uncertainty and conflicts, allowing them to accept more liberal views."

It remains unclear whether the structural differences cause the divergence in political views, or are the effect of them.

But the central issue in determining political views appears to revolve around fear and how it affects a person.

"Our findings are consistent with the proposal that political orientation is associated with psychological processes for managing fear and uncertainty," the study said.

http://news.yahoo.com/s/afp/20110407/ts_alt_afp/healthpoliticsusbritain

請參考本城市：

'Liberal gene' discovered by scientists (《政治傾向和基因》) - Telegraph.uk一文, https://city.udn.com/2976/4249925?tpno=1&cate_no=52524

Is Homosexuality Based on a Brain Chemical?

Janelle Weaver, LiveScience Contributor

A male mouse's desire to mate with either a male or a female is determined by the brain chemical serotonin, scientists report in a new study. The finding demonstrates for the first time that a neurotransmitter governs sexual preference in mammals.

Serotonin is known to regulate sexual behaviors, such as erection, ejaculation and orgasm, in both mice and men. The compound generally dampens sexual activity; for instance, antidepressants that increase the amount of serotonin in the brain sometimes decrease sex drive. [Top 10 Aphrodisiacs]

Neuroscientist Yi Rao of Peking University and the National Institute of Biological Sciences in Beijing, and his collaborators have now shown that serotonin also underlies a male's decision to woo a female or another male. They published their results in the March 24 issue of the journal Nature.

Rao and his team genetically engineered male mice to lack either serotonin-producing neurons or a protein that is crucial for making serotonin in the brain. Both types of altered mouse couldn't make serotonin.

Unlike typical males, mice deficient in the neurotransmitter showed no inclination to mount sexually receptive females more than males, nor did they prefer to smell females' genital odors or bedding. Instead, they climbed onto males and serenaded them with ultrasonic love songs more frequently than normal. Males emit these vocalizations when they encounter females to make them more receptive to mating.

While all of the males who possessed serotonin mounted females first, nearly half of the mice that lacked serotonin clambered onto males before females, and about 60 percent spent more time sniffing or hovering over the genital odors and bedding from males than from females.

When the researchers injected a compound into these mice to restore neurotransmitter levels, they found that the animals mounted females more than males. But too much serotonin reduced male-female mounting, suggesting that the amount of this chemical must stay within a certain range to foster heterosexual rather than homosexual behaviors. 

"An unavoidable question raised by our findings is whether [serotonin] has a role in sexual preference in other animals," the authors wrote in the paper. But one of the co-authors, neuroscientist Zhou-Feng Chen of Washington University, cautioned against forming hasty conclusions about the potential influence of this neurotransmitter on human sexual orientation.      

Elaine Hull, an expert in rodent sexual behavior at Florida State University who was not involved in the study, said that the findings "may have implications for homosexuality or bisexual behavior in humans," adding that the neurotransmitter could help to guide sexual development.

Still, she agreed with Chen, cautioning against overinterpreting the results.

"A lot of people are going to be reading more into this than may or may not be warranted," Hull told LiveScience. "Much more information is needed to specify the brain areas involved and possible developmental regulation of serotonin in those areas, before we can jump to the conclusion that serotonin is the factor that inhibits male-to-male attraction."

You can follow LiveScience on Twitter @livescience.

• 5 Myths About Gay People Debunked

• 10 Things You Didn't Know About the Brain

• 6 (Other) Great Things Sex Can Do For You

http://news.yahoo.com/s/livescience/20110327/sc_livescience/ishomosexualitybasedonabrainchemical

The Brain in 3-D: New Research Illuminates Cell Circuits

Janelle Weaver, LiveScience

For the first time, scientists have reconstructed a three-dimensional circuit of connected cells in the brain's seat of consciousness. Their new approach, which involves the use of high-tech microscopes and a supercomputer, offers the unprecedented opportunity to unravel the complex wiring of the brain by navigating through the tangled and dense jungle of cells — similar to the way Google crawls the Web.

The research, published by two separate teams in the March 10 issue of the journal Nature, demonstrates the possibility of tackling questions about brain function that traditional methods can't address. One study was led by neurobiologist Clay Reid of Harvard University, and the other was spearheaded by Winfried Denk at the Max Planck Institute for Medical Research in Heidelberg, Germany. [Image of brain-cell map]

As brain-imaging techniques advance, scientists have had great success looking at the activity of brain cells. While this answers the "what are they doing" question, it hasn't shed light on the "how are they doing it" mystery.

So the researchers turned to the cerebral cortex, the outside layer of the brain implicated in higher-order mental functions, including memory.

"Cortical circuits are very big, and so far we've been looking at networks of cells wired two cells at a time, or a handful of connections at a time," Reid told LiveScience. "This combination of techniques gives us the hope that in the coming decade we'll be able to look and see the physiology of literally every cell in a local network."

The individual techniques Reid used are not new, but he and his team developed painstaking procedures for matching brain-structure data with neural recordings to recreate a circuit in the visual system of mice.

They first had lab mice view lit-up bars on a screen as they measured the activity of about a dozen neurons known to play a role in mouse vision.

To figure out how these neurons were physically connected into a circuit, the researchers then turned to the electron microscope (EM), which produced high-resolution images of the animals' brain tissues by beaming electrons onto more than 1,200 tiny, adjacent slices of the brain.

They used a supercomputer to stitch together millions of high-resolution images, resulting in a three-dimensional map that looked like a forest of indecipherable wires, Reid said.

To locate the data of interest within the microscope images, the researchers manually traced the neurons they had already recorded and mapped out hundreds of their connections with nearby cells.

They focused on 10 brain cells that seemed to be critical to vision in the mice. "They spent three months of their lives drawing three-dimensional stick figures of the 10 neurons," Reid said. They essentially crawled through the brain's dense thicket, jumping from neuron to neuron to create a partial diagram of the mouse brain's visual circuit, helping to answer the question, "How does the brain see?" Reid said. [Effort to Map Human Brain Faces Complex Challenges]

Recent progress in data collection, storage and processing made the research possible, and further advances will allow scientists to probe circuits of hundreds or thousands of neurons, Reid said. "That's when it really will get interesting: when we have a much bigger and more densely connected network."

“This study is not the last word,” Reid added. “It’s very much the first attempt at something that’s very exciting that we hope will give a lot of answers in the coming years.”

10 Things You Didn't Know About the Brain 

Brain X Prize May Spur Big Solutions 

Top 10 Mysteries of the Mind 

http://news.yahoo.com/s/livescience/20110318/sc_livescience/thebrainin3dnewresearchilluminatescellcircuits

Criminal Minds Are Different From Yours, Brain Scans Reveal

LiveScience.com 

The latest neuroscience research is presenting intriguing evidence that the brains of certain kinds of criminals are different from those of the rest of the population.

While these findings could improve our understanding of criminal behavior, they also raise moral quandaries about whether and how society should use this knowledge to combat crime.

The criminal mind

In one recent study, scientists examined 21 people with antisocial personality disorder – a condition that characterizes many convicted criminals. Those with the disorder "typically have no regard for right and wrong. They may often violate the law and the rights of others," according to the Mayo Clinic.

Brain scans of the antisocial people, compared with a control group of individuals without any mental disorders, showed on average an 18-percent reduction in the volume of the brain's middle frontal gyrus, and a 9 percent reduction in the volume of the orbital frontal gyrus – two sections in the brain's frontal lobe.

Another brain study, published in the September 2009 Archives of General Psychiatry, compared 27 psychopaths — people with severe antisocial personality disorder — to 32 non-psychopaths. In the psychopaths, the researchers observed deformations in another part of the brain called the amygdala, with the psychopaths showing a thinning of the outer layer of that region called the cortex and, on average, an 18-percent volume reduction in this part of brain.

"The amygdala is the seat of emotion. Psychopaths lack emotion. They lack empathy, remorse, guilt," said research team member Adrian Raine, chair of the Department of Criminology at the University of Pennsylvania, at the annual meeting of the American Association for the Advancement of Science in Washington, D.C., last month.

In addition to brain differences, people who end up being convicted for crimes often show behavioral differences compared with the rest of the population. One long-term study that Raine participated in followed 1,795 children born in two towns from ages 3 to 23. The study measured many aspects of these individuals' growth and development, and found that 137 became criminal offenders.

One test on the participants at age 3 measured their response to fear – called fear conditioning – by associating a stimulus, such as a tone, with a punishment like an electric shock, and then measuring people's involuntary physical responses through the skin upon hearing the tone.

In this case, the researchers found a distinct lack of fear conditioning in the 3-year-olds who would later become criminals. These findings were published in the January 2010 issue of the American Journal of Psychiatry.

Neurological base of crime

Overall, these studies and many more like them paint a picture of significant biological differences between people who commit serious crimes and people who do not. While not all people with antisocial personality disorder — or even all psychopaths — end up breaking the law, and not all criminals meet the criteria for these disorders, there is a marked correlation.

"There is a neuroscience basis in part to the cause of crime," Raine said.

What's more, as the study of 3-year-olds and other research have shown, many of these brain differences can be measured early on in life, long before a person might develop into actual psychopathic tendencies or commit a crime.

Criminologist Nathalie Fontaine of Indiana University studies the tendency toward being callous and unemotional (CU) in children between 7 and 12 years old. Children with these traits have been shown to have a higher risk of becoming psychopaths as adults.

"We're not suggesting that some children are psychopaths, but CU traits can be used to identify a subgroup of children who are at risk," Fontaine said.

Yet her research showed that these traits aren't fixed, and can change in children as they grow. So if psychologists identify children with these risk factors early on, it may not be too late.

"We can still help them," Fontaine said. "We can implement intervention to support and help children and their families, and we should."

Neuroscientists' understanding of the plasticity, or flexibility, of the brain called neurogenesis supports the idea that many of these brain differences are not fixed. [10 Things You Didn't Know About the Brain]

"Brain research is showing us that neurogenesis can occur even into adulthood," said psychologist Patricia Brennan of Emory University in Atlanta. "Biology isn’t destiny. There are many, many places you can intervene along that developmental pathway to change what's happening in these children."

Furthermore, criminal behavior is certainly not a fixed behavior.

Psychologist Dustin Pardini of the University of Pittsburgh Medical Center found that about four out of five kids who are delinquents as children do not continue to offend in adulthood.

Pardini has been researching the potential brain differences between people with a past criminal record who have stopped committing crimes, and those who continue criminal behavior. While both groups showed brain differences compared with non-criminals in the study, Pardini and his colleagues uncovered few brain differences between chronic offenders and so-called remitting offenders.

"Both groups showed similar results," Pardini said. "None of these brain regions distinguish chronic and remitting offenders."

Ethical quandaries

Yet even the idea of intervening to help children at risk of becoming criminals is ethically fraught.

"Do we put children in compulsory treatment when we've uncovered the risk factors?" asked Raine. "Well, who decides that? Will the state mandate compulsory residential treatment?"

What if surgical treatment methods are advanced, and there is an option to operate on children or adults with these brain risk factors? Many experts are extremely hesitant to advocate such an invasive and risky brain intervention — especially in children and in individuals who have not yet committed any crime.

Yet psychologists say such solutions are not the only way to intervene.

"You don’t have to do direct brain surgery to change the way the brain functions," Brennan said. "You can do social interventions to change that."

Fontaine's studies, for example, suggest that kids who display callous and unemotional traits don't respond as well to traditional parenting and punishment methods such as time-outs. Instead of punishing bad behavior, programs that emphasize rewarding good behavior with positive reinforcement seem to work better.

Raine and his colleagues are also testing whether children who take supplemental pills of omega-3 fatty acids — also known as fish oil — can show improvement. Because this nutrient is thought to be used in cell growth, neuroscientists suspect it can help brain cells grow larger, increase the size of axons (the part of neurons that conducts electrical impulses), and regulate brain cell function.

"We are brain scanning children before and after treatment with omega-3," Raine said. "We are studying kids to see if it can reduce aggressive behavior and improve impaired brain areas. It's a biological treatment, but it's a relatively benign treatment that most people would accept."

'Slippery slope to Armageddon'

The field of neurocriminology also raises other philosophical quandaries, such as the question of whether revealing the role of brain abnormalities in crime reduces a person's responsibility for his or her own actions.

"Psychopaths know right and wrong cognitively, but don't have a feeling for what's right and wrong," Raine said. "Did they ask to have an amygdala that wasn't as well functioning as other individuals'? Should we be punishing psychopaths as harshly as we do?"

Because the brain of a psychopath is compromised, Raine said, one could argue that they don't have full responsibility for their actions. That — in effect — it's not their fault.

In fact, that reasoning has been argued in a court of law. Raine recounted a case he consulted on, of a man named Herbert Weinstein who had killed his wife. Brain scans subsequently revealed a large cyst in the frontal cortex of Weinstein's brain, showing that his cognitive abilities were significantly compromised.

The scans were used to strike a plea bargain in which Weinstein's sentence was reduced to only 11 years in prison.

"Imaging was used to reduce his culpability, to reduce his responsibility," Raine said. "Yet is that not a slippery slope to Armageddon where there's no responsibility in society?"

You can follow SPACE.com senior writer Clara Moskowitz on Twitter @ClaraMoskowitz.

Top 10 Controversial Psychiatric Disorders 

What Makes a Psychopath? Answers Remain Elusive 

Top 10 Mysteries of the Mind 

http://news.yahoo.com/s/livescience/20110307/sc_livescience/criminalmindsaredifferentfromyoursbrainscansreveal

What Your Brain Looks Like After 20 Years of Marriage

Belinda Luscombe, 0111/11 |

Contrary to popular opinion, people who say they are still madly in love with their spouses after more than two decades are not crazy. At least, some of them aren't. And in answer to your next question, apparently they're not lying either. This is the proposition of a new study  published in the December issue of Social Cognitive and Affective Neuroscience that took brain scans of long-married people who claimed to still be besotted with their marital partner.

The prevailing theory on romantic love is that it more or less serves the same purpose as the booster rocket in expeditions into outer space. The initial tingly can't-think-about-anything-else swooning launches the couple into orbit, but falls away after the spacecraft reaches a certain altitude, to be replaced by "companionate love," a more regulated, less passionate affection that binds two people, bolting them together with shared history and interests. (More on TIME.com: 5 Reasons to Get or Stay Married This Year)

Companionate love gets a bit of a bad rap in some corners, since it can feel to some a little too much like orbiting outer space: cold, airless and seemingly interminable.

But there are couples who claim more than this, who claim to still be knee-bucklingly in love with their partners, for whom the orbit is not dreary, but a wonderful journey with their North Star. One of the theories on these individuals is that they're kidding themselves, or fronting. Another is that they're mentally unhealthy, or generally obsessive.

Bianca Acevedo and Arthur Aron, both in the Psychology Department at Stony Brook University in New York, and their co-authors, decided to investigate. They found 17 people who claim to still be madly in love with their spouses, even after an average of 21 years of marriage. While an fMRI scanned the brain, each partner looked at a picture of his or her beloved.

They compared these brain scans with those of people who have recently fallen in love. In several key ways they looked very similar. (More on TIME.com: The Divorce So Bad it Made the Family Judge Flip Out)

It's already known that newly in love individuals show activity in dopamine-rich areas when they view images of — or think about — their significant others. This means the Ventral Tegmental Area (VTA), which is part of the reward center, shows a lot of activity. (This is also the area that lights up on the brain scans of addicts when they take cocaine.) And sure enough, in scans of couple still moony after two decades, there it is again.

But, unlike those who are newly in love, the long-in-love brains show no activity among the areas that are commonly associated with anxiety and fear. "Individuals in long-term relationships may experience the excitement, sexual attraction, engagement, and intensity associated with romantic love," says Acevedo. "But they report pining, anxiety, intrusive thinking far less than individuals newly in love."

The brain scans echo this. In fact, they show not just the absence of anxiety, but its opposite. "Interestingly, we found activation of opiate-rich sites, such as the posterior globus pallidus," says Acevedo. "These sites are associated with pleasure and pain relief. They are also activated by primary rewards such as food, and substances such as morphine." (More on Time.com: Can an iPhone App Save Your Marriage?)

Not surprisingly the scans also show a lot more activation in brain regions that are associated with maternal love, or pairs bonding. This doesn't mean people want to mother their spouses, but just that the attachments formed are similar to those that grow between mothers and their new children.

The study then compared the resulting scans with those of people looking at pictures of good friends and little known acquaintances, to make clear what was the result of  fondness and what was the real-soulmate-deal. Pairs bonding is evident there too, but not as strongly.

What are the implications of all this? Well, some of it, warns Aron, the study's co-author, may bum people out. "This is not something long term couples want to hear," he says, about people's undimming passion for their mates. "Nobody wants to hear about couples doing better than they are. We all like to believe we're the best."

The authors recommend that marital therapists not dismiss romantic love as a possible and desirable outcome in a marriage—as opposed to just aiming for conflict-resolution and better communication skills.

Aron's other research has led him to believe the most successful couples are those in which partners help each other expand their ideas of themselves. He also notes the couples who were still in love reported having sex frequently (adjusted for age, natch) although it's not clear whether this is an expression of their undying passion or a cause of it.

Envy about others' more epic love-stories aside, the study is good news for fans of long-term marriage of any type: "Romantic love need not be replaced with companionate love," says Acevedo. "Both can co-exist."

http://healthland.time.com/2011/01/11/what-your-brain-looks-like-after-20-years-of-marriage/

Chess experts use brain differently than amateurs

法新社，01/20/11

WASHINGTON (AFP) – Experts use different parts of their brains than amateurs, maximizing intuition, goal-seeking and pattern-recognition, says a new study that examined players of shogi, or Japanese chess.

Researchers used magnetic resonance imaging (MRI) scans to compare the brain activity of amateurs and professionals who were presented with various shogi board patterns and were told to think of their next move.

They found that certain regions of expert brains lit up, while the amateurs' did not, said the research led by Japan-based scientist Xiaohong Wan and published in the journal Science on Thursday.

When they asked players to mull their next move, experts' brains showed more activity in the area associated with visualizing images and episodic memory, known as the precuneus area of the parietal lobe.

When pressed to come up quickly with a move, activity surged in another region called the caudate nucleus, where goal-directed behavior is rooted.

"This activation did not occur in the amateurs or when either group took their time in planning their next move," said the study.

Researchers believe that experts who train for years in shogi are actually perfecting a circuit between the two regions that helps them quickly recognize the state of the game and choose the next step.

"Being 'intuitive' indicates that the idea for a move is generated quickly and automatically without conscious search, and the process is mostly implicit," said the study.

"This intuitive process occurs routinely in experts, and thus it is different from inspiration, which occurs less frequently and unpredictably."

http://news.yahoo.com/s/afp/20110121/sc_afp/sciencejapangame

本文於 修改第 2 次

Study shows how brain's wiring develops in babies

Kate Kelland

LONDON (Reuters) – British scientists have shown for the first time how our brain "wiring" develops in the first few months of life and say their findings will help in the understanding of a range of brain and psychiatric disorders.

Using a new imaging technique, researchers from the Institute of Psychiatry at King's College London scanned babies brains to monitor the formation of insulating layers around nerve cells.

They found that by the age of nine months, the process -- known as myelination and vital for normal brain function -- was visible in all brain areas and in some regions had developed to a near adult-like level.

"We already know that insulating myelin sheaths form the cornerstone of our neurodevelopment. Without them, messages to and from the brain would be in disarray," said Sean Deoni, who led the study, published by the Journal of Neuroscience.

"By understanding exactly how myelin develops and when this process breaks down, we hope to be able to tailor treatments for vulnerable patients, such as premature babies, and understand what differentiates those that develop normally from those who have some delay or disability."

Damage to the myelination process is thought to contribute to a range of neurological and psychiatric illnesses, including autism and mental disability.

In very premature babies, myelination can be particularly prone to damage, and the researchers said they hoped their new imaging technique would in future allow doctors to directly measure whether the treatments given to premature babies are able to help normal brain development.

Deoni's team scanned 14 healthy babies who were born at full term. They were scanned while they were asleep using a specially-modified, quiet, baby-friendly MRI scanner.

To build up a picture of their myelin development, the scientists scanned the infants monthly between 3 and 11 months and found that by 9 months, they could see that myelination had taken place in all areas of the brain.

"Until now, we've not been able to show how myelination develops in babies but this new MRI technique allows us to do just that," said Declan Murphy, also from King's College London, who oversaw the research.

He said the technique could now be used to understand how differences in the way brains are wired up relate to neurological and mental disorders that may not become obvious until later in life.

"The next step to scan premature babies and see how their myelin development differs from babies born full term, and how connections in the brains of babies who are at greater risk for developing autism differ from others," he said.

(Editing by Maria Golovnina)

http://news.yahoo.com/s/nm/20110111/sc_nm/us_brain_wiring

Study: Love music? Thank a substance in your brain

Malcolm Ritter, Ap Science Writer

NEW YORK – Whether it's the Beatles or Beethoven, people like music for the same reason they like eating or having sex: It makes the brain release a chemical that gives pleasure, a new study says.

The brain substance is involved both in anticipating a particularly thrilling musical moment and in feeling the rush from it, researchers found.

Previous work had already suggested a role for dopamine, a substance brain cells release to communicate with each other. But the new work, which scanned people's brains as they listened to music, shows it happening directly.

While dopamine normally helps us feel the pleasure of eating or having sex, it also helps produce euphoria from illegal drugs. It's active in particular circuits of the brain.

The tie to dopamine helps explain why music is so widely popular across cultures, Robert Zatorre and Valorie Salimpoor of McGill University in Montreal write in an article posted online Sunday by the journal Nature Neuroscience.

The study used only instrumental music, showing that voices aren't necessary to produce the dopamine response, Salimpoor said. It will take further work to study how voices might contribute to the pleasure effect, she said.

The researchers described brain-scanning experiments with eight volunteers who were chosen because they reliably felt chills from particular moments in some favorite pieces of music. That characteristic let the experimenters study how the brain handles both anticipation and arrival of a musical rush.

Results suggested that people who enjoy music but don't feel chills are also experiencing dopamine's effects, Zatorre said.

PET scans showed the participants' brains pumped out more dopamine in a region called the striatum when listening to favorite pieces of music than when hearing other pieces. Functional MRI scans showed where and when those releases happened.

Dopamine surged in one part of the striatum during the 15 seconds leading up to a thrilling moment, and a different part when that musical highlight finally arrived.

Zatorre said that makes sense: The area linked to anticipation connects with parts of the brain involved with making predictions and responding to the environment, while the area reacting to the peak moment itself is linked to the brain's limbic system, which is involved in emotion.

The study volunteers chose a wide range of music — from classical and jazz to punk, tango and even bagpipes. The most popular were Barber's Adagio for Strings, the second movement of Beethoven's Ninth Symphony and Debussy's Claire de Lune.

Since they already knew the musical pieces they listened to, it wasn't possible to tell whether the anticipation reaction came from memory or the natural feel people develop for how music unfolds, Zatorre said. That question is under study, too.

Dr. Gottfried Schlaug, an expert on music and the brain at Harvard Medical School, called the study "remarkable" for the combination of techniques it used.

While experts had indirect indications that music taps into the dopamine system, he said, the new work "really nails it."

Music isn't the only cultural experience that affects the brain's reward circuitry. Other researchers recently showed a link when people studied artwork.

Online:

http://www.nature.com/neuro

http://news.yahoo.com/s/ap/20110109/ap_on_sc/us_sci_music_on_the_brain

本文於 修改第 1 次

Study ties brain structure size to socializing

Malcolm Ritter, Ap Science Writer 

NEW YORK – Do you spend time with a lot of friends? That might mean a particular part of your brain is larger than usual.

It's the amygdala, which lies deep inside. Brain scans of 58 volunteers in a preliminary study indicated that the bigger the amygdala, the more friends and family the volunteers reported seeing regularly.

That makes sense because the amygdala is at the center of a brain network that's important for socializing, says Lisa Feldman Barrett, an author of the work published online Sunday by the journal Nature Neuroscience.

For example, the network helps us recognize whether somebody is a stranger or an acquaintance, and a friend or a foe, said Barrett, of Northeastern University in Boston.

But does having a bigger amygdala lead to more friends, or does socializing with a lot of friends create a bigger amygdala? The study can't sort that out. But Barrett said it might be a bit of both.

She said her study now must be replicated by further research.

The work, supported by the federal government, was aimed at uncovering basic knowledge rather than producing any immediate practical payoff, she said. But it might someday lead to ways to help people maintain active social lives, she said.

People have one amygdala in the left half of the brain and another in the right half. The findings of the new study held true for each one.

Arthur Toga, a brain-mapping expert at the University of California, Los Angeles, who didn't participate in the study, called the work well done and the statistical results strong. The idea of linking a brain structure to human behavior is "interesting and important," he said.

Amygdala research made headlines earlier this month when researchers reported on a woman without a working amygdala. The woman felt no fear in threatening situations.

Online:

http://www.nature.com/neuro

http://news.yahoo.com/s/ap/20101226/ap_on_sc/us_sci_social_brain

Woman With No Fear Intrigues Scientists

Jeanna Bryner, LiveScience Managing Editor

A 44-year-old woman who doesn't experience fear has led to the discovery of where that fright factor lives in the human brain.

Researchers put out their best foot to try to scare the patient, who they refer to as "SM" in their write-up in the most recent issue of the journal Current Biology. Haunted houses, where monsters tried to evoke an avoidance reaction, instead evoked curiosity; spiders and snakes didn't do the trick; and a battery of scary film clips entertained SM.

The patient has a rare condition called Urbach-Wiethe disease that has destroyed her amygdala, the almond-shaped structure located deep in the brain. Over the past 50 years studies have shown the amygdala plays a central role in generating fear responses in various animals from rats to monkeys.

The new study involving SM is the first to confirm that brain region is also responsible for experiencing fear in humans. "This is the first study to systematically investigate the experience or feeling of fear in humans with amygdala damage," lead author Justin Feinstein told LiveScience.

The finding, the researchers say, could lead to treatments for post-traumatic stress disorder (PTSD) in soldiers and others. "My hope is to expand on this work and search for psychotherapy treatments that selectively target and dampen down hyperactivity in the amygdala of patients with PTSD," said Feinstein, who is a doctoral student studying clinical neuropsychology at the University of Iowa.

Over the past year, Feinstein has been treating PTSD in veterans coming back from Iraq and Afghanistan, seeing first-hand the effects.

"Their lives are marred by fear, and they are oftentimes unable to even leave their home due to the ever-present feeling of danger," Feinstein said. In contrast, SM is immune to this stress. "Traumatic events leave no emotional imprint on her brain," he said.

Are you scared?

Previous studies with this patient revealed she can't recognize fear in facial expressions, but it was unknown if she had the ability to experience fear herself.

To find out, Feinstein and his colleagues measured the patient's experience of fear with several standardized questionnaires that probed different aspects of fear, ranging from the fear of death to the fear of public speaking. [Fear of Spiders & 9 Other Phobias]

In addition, for three months SM carried a computerized emotion diary that randomly asked her to rate her current fear level throughout the day. The diary also had her indicate emotions she was feeling from a list of 50 items. Her average score of fear was 0 percent, while for other emotions she showed normal functioning.

Across all of the scenarios, she showed no fear. Looking into her past, the researchers found lots of reasons for her to react with fear. In fact, she told them she didn't like snakes, but when brought into contact with the two characters, she was fearless.

The good and bad of being fearless

Her eldest son (she has three children) in his early 20s recalls this instance: "Me and my brothers were playing in the yard and mom was outside sitting on the porch. All of a sudden we see this snake on the road. It was a one lane road, and seriously, it touched from one end of the yard all the way to the other side of the road. I was like, 'Holy cow, that's a big snake!' Well mom just ran over there and picked it up and brought it out of the street, put it in the grass and let it go on its way..."

That's not all. She has been held up at knife point and at gun point, physically accosted by a woman twice her size, nearly killed in an act of domestic violence, and on more than one occasion explicitly threatened with death, the researchers wrote in the journal article. Police reports corroborated these experiences and revealed the poverty-stricken area where she lived. SM has never been convicted of a crime.

"What stands out most is that, in many of these situations, SM's life was in danger, yet her behavior lacked any sense of desperation or urgency," the researchers wrote.

And when she was asked to recollect how she felt during those situations, SM said she didn't feel fear but did feel upset and angry about what happened. "Without fear, it can be said that SM's distress lacks the deep heartfelt intensity endured by most survivors of trauma," the researchers wrote.

Essentially, due to the amygdala damage the woman is "immune to the devastating effects of posttraumatic stress disorder," they wrote.

As always, there are tradeoffs as such an inability to detect and avoid threatening situations likely contributed to the frequency with which she's had life-threatening run-ins, the researchers suggest.

To firm up the phenomenon, Feinstein says studying other patients with damaged amygdalas would be great. "Unfortunately, such patients are so rare that it is nearly impossible to find them," he said, adding that there is much to be learned from a single patient.

The National Institutes of Health and a National Science Foundation Graduate Fellowship provided funding for the study.

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