How City Living Stresses the Brain

Jennifer Welsh, LiveScience Staff Writer

City living can be tough on the brain — it's been linked to anxiety, depression and schizophrenia. By testing the brains of students raised or living in cities, researchers in Germany have located the brain areas linked to this stress reaction.

Previous studies have shown that city living during childhood is associated with a two- to three-fold greater chance of getting schizophrenia, and even after reaching adulthood, living in a city increases the risk for anxiety disorders by 21 percent and mood disorders by 39 percent compared with non-urban dwellers.

"If everyone was born in the country, there would be 30 percent fewer people with schizophrenia, which is a sizable reduction," said study researcher Andreas Meyer-Lindenberg, of the University of Heidelberg in Mannheim, Germany. "But, if everyone was born in the country, it would become crowded."

Big city living

To find out how city living may change the brain, the researchers scanned the brains of German students while they underwent social stress: The students were given math tests on an adaptive program that let them get only a third of the questions correct.

The program also indicated to each student that he or she had performed worse on the test than anyone who had taken it; meanwhile, the researchers pushed them to do better, telling them how important it was to perform well on the test.

During the stressful task, students who were living in cities showed increased activity in a brain region called the perigenual anterior cingulate cortex (PACC), while those who lived in cities in their early childhood (regardless of where they lived at present) showed increased activity in the amygdala. These increases were in comparison with non-city dwellers. [10 Things You Didn’t Know About the Brain]

"We were quite surprised it was that specific," Meyer-Lindenberg said. "Those two brain areas are separate but they are linked, they form a circuit."

Stressed brain regions

The amygdala and the perigenual anterior cingulate cortex together form a stress-response pathway in the brain, with the PACC regulating the amygdala, which then helps you process threats and temper your emotional reactions.

The researchers are looking next to see what parts of city living might influence this difference in brain activity, including factors like amount of green space available, type of neighborhood and culture of the region. These insights could help city planners build better, less anxiety-producing cities.

"We can't evade living in cities, and I'm not arguing we should," Meyer-Lindenberg told LiveScience. "But, what about the urban experience is it that influences our brains? If we find that, we can try to address it by city planning."

The study was published today (June 22) in the journal Nature.

You can follow LiveScience staff writer Jennifer Welsh on Twitter @microbelover. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

• Top 10 Controversial Psychiatric Disorders 
• Understanding the 10 Most Destructive Human Behaviors 
• Top 10 Mysteries of the Mind 

http://news.yahoo.com/s/livescience/20110622/sc_livescience/howcitylivingstressesthebrain

Can Brain Scans Predict Pop Hits?

Jennifer Welsh, LiveScience Staff Writer

What makes a song popular? A teen's brain seems to know, even if he or she won't admit to actually liking the song.

In a study originally designed to determine the effect of peer pressure on teens' song choices, Gregory Berns of Emory University asked 27 teens, ages 12 to 17, listen to snippets from 120 unknown artists while he scanned their brains. The music was picked from unsigned artists on MySpace in 2006.

It wasn't until 2009, when Berns heard Kris Allen sing "Apologize" by One Republic on the FOX television show "American Idol," that he realized some of the songs he had used in the original study, such as "Apologize," might have become popular.

"It occurred to me that we had this unique data set of the brain responses of kids who listened to songs before they got popular," Berns said in a statement. "I started to wonder if we could have predicted that hit."

Predictive brainpower

He decided to take a second look at the three-year-old data, to determine if there was a correlation between the teens' brains or their ratings of the music and song sales (from 2007 to 2010, as calculated by the Nielsen Company). When the teens were listening to songs later found to become popular, the reward centers of their brains were more active than when listening to future duds, he found. [Read: 10 Facts About a Teen's Brain]

"You really can't fake the brain responses while you're listening to the song," Berns said. "That taps into a raw reaction."

The correlation wasn't perfect, but it was significant enough. Of the top 10 reward-center activating songs, five of the songs sold more than 50,000 copies. However, three that weren't in the neural-activating top 10 were the only songs selling more than 500,000 (the industry standard "hit").

This correlation didn't show up in the teens' actual ratings of the songs, which Berns theorizes can be complicated by their thought processes. “You have to stop and think, and your thoughts may be colored by whatever biases you have, and how you feel about revealing your preferences to a researcher," Berns said.

Population-level predictions

The study is limited by its small, specialized sample of teenagers. It's possible using a more diverse crowd could help increase predictive value of the sample. Also, the majority of the 120 songs used in the study didn't hit high sales numbers. Only three sold more than 500,000 copies.

This study is part of a new field, called "neuroeconomics," in which brain scans from a group of individuals are used to cultural phenomenon across a population. So far, this method has been used to determine the decision-making effects of everything from product packaging to politics.

“My long-term goal is to understand cultural phenomena and trends," Berns said. "I want to know where ideas come from, and why some of them become popular and others don't. … Ultimately, I’m trying to predict history."

The study will be published in a forthcoming issue of the Journal of Consumer Psychology.

You can follow LiveScience staff writer Jennifer Welsh on Twitter @microbelover. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

• 10 Facts Every Parent Should Know about Their Teen's Brain 
• 7 Ways the Mind and Body Change With Age 
• Top 10 Mysteries of the Mind 

http://news.yahoo.com/s/livescience/20110614/sc_livescience/canbrainscanspredictpophits

3-D Images Reveal What Happens as Brain Loses Consciousness

Jennifer Welsh, LiveScience Staff Writer

New 3-D images reveal for the first time what happens inside the brain when a person loses consciousness, suggesting the mysterious sleeplike state occurs as electrical activity deep in the brain dims and connections between certain neurons suddenly break down.

"We have produced what I think is the first video in existence in the entire world of [the brain of] a patient being anesthetized," said study researcher Brian Pollard, of the University of Manchester. "We are seeing different parts of the brain, different areas, being activated and deactivated."

Loss of consciousness occurs when the brain is no longer aware of one's surroundings and so the body stops reacting to the world around it. Scientists and doctors aren't sure how this happens, but distinguish it from consciousness, or the ability to understand, be self-aware and think in the unique way that humans do. [Top 10 Mysteries of the Mind]

Previous theories, by Dr. Susan Greenfield of the University of Oxford, suggest that our brains are on a "dimmer switch," a theory supported by the new data. Here's how it works: When we're awake, certain groups of brain cells interact and work together to decipher information sent to the brain. When this "dimming switch" gets turned down — as would happen with an anaesthetic drug — these brain-cell interactions don't work as well together and communication between the groups is inhibited.

A new imaging method allowed the researchers to monitor the electrical activity deep inside the brain in real time through 32 electrodes on the head of each study participant. Because the electrodes monitor this activity 100 times per second, the researchers were literally able to watch as patients went from awake to an unconscious state.

With the technique, the team has studied the brain activity in 20 healthy adults, who will serve as controls; the researchers will compare the brain activity of controls with that of patients undergoing surgery (and being "put under"), so they can get a better handle on how a person loses consciousness. []

They have studied 17 patients losing consciousness so far, and all show similar patterns of activity deep within the brain.

Pollard could even see unconscious patients' visual cortex working when he appeared in their frame of view. "The patient is lying still and quietly and there is some activity in the right hand side of the brain, what we suspect is the visual cortex," Pollard told LiveScience. "We observed in the brain the patient seeing me."

"We aren't entirely certain what it means. We are seeing it for the first time," Pollard said. 

The device could be useful for monitoring head injury, stroke or dementia patients, to see how their brain activity changes with their condition, Pollard added.

The research will be presented at the European Anaesthesiology Congress on June 11.

You can follow LiveScience staff writer Jennifer Welsh on Twitter @microbelover. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

• 10 Things You Didn't Know About the Brain 
• Eye Tricks: Gallery of Visual Illusions 
• That's Incredible! 9 Brainy Baby Abilities 

http://news.yahoo.com/s/livescience/20110611/sc_livescience/3dimagesrevealwhathappensasbrainlosesconsciousness

Why Aging Makes It Hard to Learn New Tricks

Jeanna Bryner, LiveScience Managing Editor

Like the saying, "You can't teach an old dog new tricks," the aging human brain has a tough time learning from new experiences, suggests a study on rats showing tiny brain-cell structures needed for this process get quite rigid in their twilight years.

Rats are generally reliable models for human brain studies, so the results should hold for us, the researchers say.

The researchers looked at the prefrontal cortex, the brain region that controls various cognitive processes and plays a role in higher learning. They knew that brain cells in the prefrontal cortex of young animals are really flexible, or plastic. Life experiences, particularly those that involve learning, can profoundly alter the circuitry in this brain region. [10 Things You Didn't Know About the Brain]

For example, stress causes nerve cells to shrink and lose synapses, or the connections between nerve cells where communication occurs. Once the stressful experience ends, these brain cells recover — they are plastic, flexible — or at least they do in young animals.

Stressed brain

To find out how stress affects this plasticity in aging brains, the researchers exposed young, middle-age and old rats to a stressor known to elicit nerve cell changes in the prefrontal cortex.

After stressing out the rats, the researchers looked at close-up images of structures on nerve cells called spines that form synapses and are critical for learning. These spines "are modified when you learn something," said study researcher John Morrison, a professor of neuroscience at Mount Sinai School of Medicine. "In a sense, that's where learning occurs."

In the young rats, the brain cells lost many of their spines, which grew back after a stress-free period. However, in middle-age and old rats, the spines didn't change at all. Another change seen due to stress was a shortening of branchlike projections on neurons called dendrites. And while these dendrites recovered in young rats, they didn't in the aging rodents.

"The way we interpret that is that with aging you lose a lot of the capacity to have experience-induced plasticity," Morrison told LiveScience, adding that learning is the classic example of this type of plasticity. "So we think this gives us a really good working model for why with age you have these cognitive declines and impaired learning."

They suspect the problem occurs when a rat, or person, loses these spines as they age; the ones that go are the spry spines with lots of plasticity, leaving the more rigid ones behind. These spines can't effectively respond to stress or learning, he said.

Cognitive decline

That lack of rewiring ability may be responsible for cognitive decline in aging adults, he added.

He said that this type of study is important because it may reveal changes in brain cells that occur in an early stage of Alzheimer's disease, before the neurons actually die. It's at this early stage where doctors would want to intervene and treat the cognitive decline before it's too late, he said.

In fact, no other animal except humans show naturally occurring Alzheimer's; in animal models of the disease, researchers must modify the rats or monkeys to induce Alzheimer's.

The research is detailed in the May 25 issue of the Journal of Neuroscience.

Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

10 Ways to Keep Your Mind Sharp 

7 Ways the Mind and Body Change With Age 

10 Things You Didn't Know About the Brain 

http://news.yahoo.com/s/livescience/20110524/sc_livescience/whyagingmakesithardtolearnnewtricks

I control therefore I am: chimps self-aware, says study

Laurent Banguet And Marlowe Hood, 05/03/11

PARIS (AFP) – Chimpanzees are self-aware and can anticipate the impact of their actions on the environment around them, an ability once thought to be uniquely human, according to a study released Wednesday.

The findings, reported in the Proceedings of the Royal Society B, challenge assumptions about the boundary between human and non-human, and shed light on the evolutionary origins of consciousness, the researchers said.

Earlier research had demonstrated the capacity of several species of primates, as well as dolphins, to recognize themselves in a mirror, suggesting a fairly sophisticated sense of self.

The most common experiment consisted of marking an animal with paint in a place -- such as the face -- that it could only perceive while looking at its reflection.

If the ape sought to touch or wipe off the mark while facing a mirror, it showed that the animal recognised itself.

But even if this test revealed a certain degree self-awareness, many questions remained as to how animals were taking in the information. What, in other words, was the underlying cognitive process?

To probe further, Takaaki Kaneko and Masaki Tomonaga of the Primate Research Institute in Kyoto designed a series of three experiments to see if chimps, our closest cousins genetically, to some extent "think" like humans when they perform certain tasks.

In the first, three females initiated a video game by placing a finger on a touch-sensitive screen and then used a trackball, similar to a computer mouse, to move one of two cursors.

The movement of the second cursor, designed to distract or confuse the chimps, was a recording of gestures made earlier by the same animal and set in motion by the computer.

The "game" ended when the animal hit a target, or after a certain lapse of time.

At this point, the chimp had to identify with his finger which of the two cursors he had been manipulating, and received a reward if she chose correctly. All three animals scored above 90 percent.

"This indicates that the chimpanzees were able to distinguish the cursor actions controlled by themselves from those caused by other factors, even when the physical properties of those actions were almost identical," the researchers said.

But it was still not clear whether the good performance was truly due to the ability to discern "self-agency", or to observing visual cues and clues, so the researchers devised another set of conditions.

This time they compared two tests. The first was the same as in the previous experiment.

In the second, however, both cursors moved independently of efforts to control them, one a repeat of movements the chimp had generated in an earlier exercise, and the other a repeat of an "decoy" cursor. The trackball, in essence, was unplugged, and had no connection to the screen.

If the animals performed well on the first test but poorly on the second, the scientists reasoned, it would suggest that they were not simply responding to visual properties but knew they were in charge.

The final experiment -- used only for the most talented of the chimps -- introduced a time delay between trackball and cursor, as if the two were out of sync, and a distortion in the direction the cursor moved on the screen.

All the results suggested that "chimpanzees and humans share fundamental cognitive processes underlying the sense of being an independent agent," the researchers concluded.

"We provide the first behavioural evidence that chimpanzees can perform distinctions between self and other for external events on the basis of a self-monitoring process."

http://news.yahoo.com/s/afp/20110504/sc_afp/scienceneurosciencecognitionchimpanzees

Memory Lapses Linked to Brain Cells Napping

Stephanie Pappas, LiveScience Senior Writer

If you're staying up past your bedtime, you may not be as awake as you think you are. A new study of sleep-deprived rats finds that some of the animals' brain cells go into an "off" state even as the rats remain active and seemingly alert.

These neuronal "naps" come at a cost: Rats who experienced them became worse at reaching out to grab a sugar pellet with a single paw. The findings could explain some memory lapses that occur even when you don't feel tired, study researcher Chiara Cirelli, a psychiatrist at the University of Wisconsin, Madison School of Medicine and Public Health, said in a statement.

"Even before you feel fatigued, there are signs in the brain that you should stop certain activities that may require alertness," Cirelli said. "Specific groups of neurons may be falling asleep, with negative consequences on performance."

Cirelli and her colleagues reported their results today (April 27) in the journal Nature.

Nighttime for neurons

The importance of sleep on performance is well-known. One study, published in March 2011 in the journal Current Biology, found that taking a nap prior to memorizing information can improve how well you remember what you learned. And when people go without sleep long enough, they start to experience "microsleeps," or three to 15-second periods of sudden sleep — clearly a dangerous condition for drivers and others doing tasks requiring alertness, Cirelli and her co-authors wrote. But the new rat study suggests that brain drain may begin long before these microsleeps occur.

Cirelli and her colleagues implanted probes into the brains of 11 adult rats. The probes measured the electrical activity of neurons in the frontal cortex, the area of the brain that sits behind the forehead in humans. The researchers then deprived the rats of sleep for four hours, distracting them with new toys and videotaping them to be sure they stayed awake. Four hours of sleep deprivation isn't much for a rat, Cirelli told LiveScience.

"It would probably be like one night or even less of deprivation for a human," she said.

As the four hours wore on, the researchers found, something strange began to happen in the rats' brains. Small segments of neurons began to go quiet, behaving as if they were in a sleeping instead of a wakeful brain. But the rest of the monitoring showed the brain to be awake — and the rats were open-eyed and active the whole time.

"This activity happened in few cells," Cirelli said. "For instance, out of 20 neurons we monitored in one experiment, 18 stayed awake. From the other two, there were signs of sleep — brief periods of activity alternating with periods of silence."

These periods of neuronal silence became more common the longer the rats stayed awake, increasing more than 57 percent from the first to the fourth hour of sleep deprivation.

The researchers tested an additional nine rats, this time inserting probes into the animals' parietal lobes, the area toward the top of the head. Again, they saw a pattern of increasingly sleepy neurons.

Sleep-deprived and struggling

To test whether the periods of neuronal silence affected the animals, the research team trained eight rats to do a task where they had to reach out for a pellet of sugar with one paw. They found that if a neuronal nap occurred in the frontal cortex 300 to 800 milliseconds before the rat tried the reaching task, the rats were  37.5 percent more likely to drop or miss the pellet when grabbing for it than if there was no off-period. In addition, the sleep-deprived rats got worse and worse at successfully grabbing the sugar the longer they stayed awake.

Cirelli said neuronal quiet periods and associated performance declines are likely to occur in humans.

"Based on what we know right now about sleep in rodents versus humans… we have little reason to doubt that something like this happens in humans," she said.

The connection between neuronal quiet periods and decreased performance is still "speculative," wrote Christopher Colwell, a sleep researcher at the University of California, Los Angeles, in an editorial accompanying the paper. (Colwell was not involved in the study.) Still, he wrote, the possible relationship should be tested further, perhaps by deliberately putting neurons to sleep and testing for consequences.

The findings open up new questions about the nature of sleep, Colwell wrote.

"Is it appropriate to think of single neurons as being asleep while the brain is awake?" he wrote. "If so, the physiological mechanisms that govern the 'on' and 'off' states will need a closer look."

Cirelli and her colleagues plan to test sleep-deprived rats on other tasks while monitoring them for neuron naps. Similar studies could be done on humans, Cirelli said, but only if they already had electrodes implanted in their brains for medical reasons. Some epilepsy patients do have temporary electrode implants, she said, which are used to pinpoint the source of their seizures. Some of these patients are also sleep-deprived in an effort to trigger and trace seizures, she said.

"These patients are undergoing sleep deprivation anyhow for clinical reasons, and therefore we could study them to find out if this phenomenon is happening in humans," she said.

In the meantime, Cirelli said, it pays to take sleep seriously.

"There are consequences of being sleep deprived even before there are obvious signs," she said.

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

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 http://news.yahoo.com/s/livescience/20110427/sc_livescience/memorylapseslinkedtobraincellsnapping

Schizophrenic Brain Cells Created in Lab

Jeanna Bryner, LiveScience Managing Editor,

Skin cells taken from four individuals with schizophrenia have been turned into brain cells, or neurons, and grown in lab dishes, the first time a complex mental disorder has been examined using living brain cells.

The lab-grown neurons showed fewer connections between each other than was found in healthy brain cells, the researchers said.

The research not only will assist scientists in understanding the causes of a mental disease that plagues about 1 percent of the world's population (and about 3 million people in the United States), but also takes a step toward personalized medicine for those afflicted.

"What's so exciting about this approach is that we can examine patient-derived neurons that are perhaps equivalent to a particular patient's own neural cells," said researcher Gong Chen, an associate professor of biology at Penn State. The method would also allow researchers to test which drugs might work best for a particular patient without that person having to try it out first, Chen added. [Image of schizophrenic brain cells]

"The patient can be his or her own guinea pig for the design of his or her own treatment, without having to be experimented on directly," Chen said.

The research is detailed in the April 13 advance online issue of the journal Nature.

Cell smarts

Challenges in studying psychiatric disorders such as schizophrenia include limited access to human brain cells as well as difficulty in teasing out genetic versus environmental influences on the disease, the researchers said.

"Nobody knows how much the environment contributes to the disease," said study researcher Kristen Brennand, a postdoctoral researcher at Salk. "By growing neurons in a dish, we can take the environment out of the equation and start focusing on the underlying biological problems." [Brain Cells in Lab Dish Keep Time]

And so the team, which also included Fred Gage, a professor in the Salk's Laboratory of Genetics, started from scratch in a way, turning the clock back on skin cells taken from four schizophrenia patients with a hereditary history of the disease. They programmed these cells to become unspecialized or undifferentiated stem cells called induced pluripotent stem cells. In this way, they avoided removing participants' neurons.

"A pluripotent stem cell is a kind of blank slate," Chen said. "During development, such stem cells differentiate into many diverse, specialized cell types, such as a muscle cell, a brain cell or a blood cell."

The team then directed the stem cells to become brain cells and compared the resulting neurons with those created from the induced pluripotent stem cells of healthy individuals.

Underpinnings of a disease

"Nobody knows how much the environment contributes to the disease," said Brennand. "By growing neurons in a dish, we can take the environment out of the equation and start focusing on the underlying biological problems."

And indeed they found some. Brennand treated the lab neurons with a modified rabies virus, which is known to travel along connections between brain cells. This tracer showed the schizophrenic neurons connected less frequently with each other and had fewer projections growing out from their cell bodies.

Genetic analysis also showed nearly 600 genes whose activity was off-kilter in these neurons, with 25 percent of these genes being linked to schizophrenia in past research.

The team tested the ability of five antipsychotic drugs — clozapine, loxapine, olanzapine, risperidone and thioridazine — to improve neuronal connectivity in the schizophrenia brain cells. Only loxapine significantly increased brain-cell connections from all schizophrenia patients, the researchers write.

At the end of the day, the results may help to counter social stigma often attached to mental disorders. "Many people believed that if affected individuals just worked through their problems, they could overcome them," Gage said. "But we are showing real biological dysfunctions in neurons that are independent of the environment."

You can follow LiveScience managing editor Jeanna Bryner on Twitter @jeannabryner.

Top 10 Controversial Psychiatric Disorders 

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http://news.yahoo.com/s/livescience/20110413/sc_livescience/schizophrenicbraincellscreatedinlab

Embarrassed? Blame Your Brain

Jennifer Welsh, LiveScience Staff Writer,

Flushed, red-hot cheeks. Sweating palms. Hearing your rendition of "My Girl" — but you aren't at karaoke. You are in the lab of Virginia Sturm at the University of California, San Francisco, and she's making you watch your own off-key rendition of The Temptations’ 1964 hit.

Sturm's team is working to isolate the part of the brain in control of embarrassment. They've found that the feeling of embarrassment that comes with experiences such as hearing your own singing is isolated to a thumb-sized bit of tissue deep within your brain.

In people who show low levels of embarrassment — including those with dementia — this brain region is smaller than normal. "This region is actually essential for this reaction. When you lose this region, you lose this embarrassment response," Sturm told LiveScience. (Most of Sturm's study participants are actually patients with dementia, including disorders such as Alzheimer's disease.)

Personality centers

The embarrassment center is focused in an area called the pregenual anterior cingulate cortex; this tissue resides deep inside your brain, to the front and the right. This region is integral in regulating many automatic bodily functions, such as sweating, heartbeat and breathing, but also participates in many thinking-related functions, including emotions, reward-searching behaviors (like those implicated in addiction) and decision-making.

"It has projections to higher centers and also has projections down to lower centers," Sturm said. "It has a dual role in both visceral and also motor reactions."

Size and shape of brain regions near this one have been associated with differences in personality. Scientists believe that the bigger a particular brain region, the more powerful the functions associated with it would be. For instance, extroverts have larger reward-processing centers, while anxious and self-conscious people have larger error-detection centers. Very giving people have larger areas associated with understanding other's beliefs, studies have shown.

Degeneration of embarrassment

Those with dementia tend to have lowered levels of embarrassment, even when watching themselves sing along to cheesy Motown hits.

Many things that those with dementia do, such as giving strangers massages or eating off of others' plates, don’t seem to embarrass them. When Sturm scanned their brains, she noticed that the less self-conscious and embarrassed the participants were, the smaller this embarrassment region in their cingulate cortex was.

Scanning this region of the brain could help diagnose these conditions earlier, since behavioral and social changes tend to happen before other symptoms that manifest themselves more obviously. "A better understanding of the emotional changes that occurring in these diseases could be helpful early in the course of disease when the diagnosis might not be so obvious," Sturm said. "There could be a host of emotional or social changes that go along with the diseases."

The work was presented in a talk by Sturm Thursday (April 14) at the 64th annual American Academy of Neurology meeting in Hawaii.

You can follow LiveScience staff writer Jennifer Welsh on Twitter @microbelover.

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http://news.yahoo.com/s/livescience/20110415/sc_livescience/embarrassedblameyourbrain

Clearing the Mind: How the Brain Cuts the Clutter

LiveScience.com 

Newly discovered neurons in the front of the brain act as the bouncers at the doors of the senses, letting in only the most important of the trillions of signals our bodies receive. Problems with these neurons could be the source of some symptoms of diseases like attention deficit disorder and schizophrenia.

"The brain doesn't have enough capacity to process all the information that is coming into your senses," said study researcher Julio Martinez-Trujillo, of McGill University in Montreal. "We found that there are some cells, some neurons in the prefrontal cortex, which have the ability to suppress the information that you aren't interested in. They are like filters."

Humans are constantly taking in huge streams of data from each of our senses. Our brains have a seeming magical ability to filter only the most important signals (like "ouch, burning!" or "ooh, shiny!"). Without this ability to filter we would suffer from sensory overload, with all stimuli constantly battling for our attention.

A cluttered mind

This "brain clutter," or inability to filter out unnecessary information, is a possible mechanism of diseases like attention deficit hyperactivity disorder (ADHD) and schizophrenia. For instance, when a student can't filter out the majority of the sensory input in a classroom, they become easily distracted and unable to focus on the task at hand. They physical symptoms of schizophrenia, which include clumsiness and random movements, could be linked to an inability to filter outgoing motor signals. [Marijuana Worsens Schizophrenia]

Previous research has linked this filtering process to the prefrontal cortex, a brain region involved in taking in external information and turning it into complex behaviors.

Martinez-Trujillo and his team discovered that specific neurons in this area take on the filtering task. They do so by downplaying the useless information you receive.

"Those cells allow you to focus on the things you are interested in and suppress everything else," Martinez-Trujillo told LiveScience.

Mindful monkeys

The researchers discovered these neurons by training monkeys to recognize a rank order of colors. The monkeys would watch a screen with two different color dots moving across the two sides. The colors were ranked arbitrarily from lower importance (gray) to highest (turquoise), and the monkeys were taught which of the colors were more important.

When the dots of the more important color changed direction momentarily, the monkey would release a button. To do the task correctly, the monkeys needed to understand which of the colors were more important and ignore the movements of the other, less important dots. After the monkeys learned this task, the researchers scanned their brains to see which neurons were firing, noticing a certain subset in the front of the brain lighting up.

The researchers also noticed that the task was harder the closer together on the rank-order scale the two colors were. This phenomenon is also seen when mentally processing numbers. Humans answer faster when asked if 9 is larger than 1 than when asked if 2 is larger than 1.

The mechanism by which they do this important task isn't clear, but when identified it could help researchers understand and treat these attention disorders. Improving these cells' ability to filter out unwanted information could help refocus attention of kids with ADHD. "It would allow those children to focus on the teacher and not be distracted by everything else around them because they can filter those things out," Martinez-Trujillo said.

The study is published in the April 13 issue of the journal Neuron.

You can follow LiveScience staff writer Jennifer Welsh on Twitter @microbelover.

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http://news.yahoo.com/s/livescience/20110413/sc_livescience/clearingthemindhowthebraincutstheclutter

Scientists find way to map brain's complexity

LONDON (Reuters) – Scientists say they have moved a step closer to developing a computer model of the brain after finding a way to map both the connections and functions of nerve cells in the brain together for the first time.

In a study in the journal Nature on Sunday, researchers from Britain's University College London (UCL) described a technique developed in mice which enabled them to combine information about the function of neurons with details of their connections.

The study is part of an emerging area of neuroscience research known as 'connectomics'. A little like genomics, which maps our genetic make-up, connectomics aims to map the brain's connections, known as synapses.

By untangling and being able to map these connections -- and deciphering how information flows through the brain's circuits -- scientists hope to understand how thoughts and perceptions are generated in the brain and how these functions go wrong in diseases such as Alzheimer's, schizophrenia and stroke.

"We are beginning to untangle the complexity of the brain," said Tom Mrsic-Flogel, who led the study.

"Once we understand the function and connectivity of nerve cells spanning different layers of the brain, we can begin to develop a computer simulation of how this remarkable organ works."

But he said would take many years of work among scientists and huge computer processing power before that could be done.

In a report of his research, Mrsic-Flogel explained how mapping the brain's connections is no small feat: There are an estimated one hundred billion nerve cells, or neurons, in the brain, each connected to thousands of other nerve cells, he said, making an estimated 150 trillion synapses.

"How do we figure out how the brain's neural circuitry works? We first need to understand the function of each neuron and find out to which other brain cells it connects," he said.

In this study, Mrsic-Flogel's team focused on vision and looked into the visual cortex of the mouse brain, which contains thousands of neurons and millions of different connections.

Using high resolution imaging, they were able to detect which of these neurons responded to a particular stimulus.

Taking a slice of the same tissue, the scientists then applied small currents to subsets of neurons to see which other neurons responded and which of them were synaptically connected.

By repeating this technique many times, they were able to trace the function and connectivity of hundreds of nerve cells in visual cortex.

Using this method, the team hopes to begin generating a wiring diagram of a brain area with a particular function, such as the visual cortex. The technique should also help them map the wiring of regions that underpin touch, hearing and movement.

John Williams, head of neuroscience and mental health at the Wellcome Trust medical charity, which helped fund the study, said understanding the brain's inner workings was one of science's "ultimate goals."

"This important study presents neuroscientists with one of the key tools that will help them begin to navigate and survey the landscape of the brain," he said.

(Reporting by Kate Kelland; Editing by Sophie Hares)

http://news.yahoo.com/s/nm/20110411/hl_nm/us_brain_model

(請參考本欄：《大腦神經網路的立體影像》)