Brain Size May Determine Whether You Are Good at Keeping Friends

Brain Size May Determine Whether You Are Good at Keeping Friends

  12:56:00 AM    Science Lover

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Researchers are suggesting that there is a link between the number of friends you have and the size of the region of the brain -- known as the orbital prefrontal cortex -- that is found just above the eyes. A new study shows that this brain region is bigger in people who have a larger number of friendships.

Friends. Researchers are suggesting that there is a link 
between the number of friends you have and the size of 
the region of the brain -- known as the orbital prefrontal 
cortex -- that is found just above the eyes. 
(Credit: © Rido / Fotolia)

Their study is published on 1 February 2012 in the journal, Proceedings of the Royal Society B.

The research was carried out as part of the British Academy Centenary 'Lucy to Language' project, led by Professor Robin Dunbar of the University of Oxford in a collaboration with Dr Joanne Powell and Dr Marta Garcia-Finana at Liverpool University, Dr Penny Lewis at Manchester University and Professor Neil Roberts at Edinburgh University.

The study suggests that we need to employ a set of cognitive skills to maintain a number of friends (and the keyword is 'friends' as opposed to just the total number of people we know). These skills are described by social scientists as 'mentalising' or 'mind-reading'- a capacity to understand what another person is thinking, which is crucial to our ability to handle our complex social world, including the ability to hold conversations with one another. This study, for the first time, suggests that our competency in these skills is determined by the size of key regions of our brains (in particular, the frontal lobe).

Professor Dunbar, from the Institute of Cognitive and Evolutionary Anthropology, explained: '"Mentalising" is where one individual is able to follow a natural hierarchy involving other individuals' mind states. For example, in the play 'Othello', Shakespeare manages to keep track of five separate mental states: he intended that his audience believes that Iago wants Othello to suppose that Desdemona loves Cassio [the italics signify the different mind states]. Being able to maintain five separate individuals' mental states is the natural upper limit for most adults.'

The researchers took anatomical MR images of the brains of 40 volunteers at the Magnetic Resonance and Image Analysis Research Centre at the University of Liverpool to measure the size of the prefrontal cortex, the part of the brain used in high-level thinking. Participants were asked to make a list of everyone they had had social, as opposed to professional, contact with over the previous seven days. They also took a test to determine their competency in mentalising.

Professor Robin Dunbar, said: 'We found that individuals who had more friends did better on mentalising tasks and had more neural volume in the orbital frontal cortex, the part of the forebrain immediately above the eyes. Understanding this link between an individual's brain size and the number of friends they have helps us understand the mechanisms that have led to humans developing bigger brains than other primate species. The frontal lobes of the brain, in particular, have enlarged dramatically in humans over the last half million years.'

Dr Joanne Powell, from the Department of Psychology, University of Liverpool, said: 'Perhaps the most important finding of our study is that we have been able to show that the relationship between brain size and social network size is mediated by mentalising skills. What this tells us is that the size of your brain determines your social skills, and it is these that allow you have many friends.'

Professor Dunbar said: 'All the volunteers in this sample were postgraduate students of broadly similar ages with potentially similar opportunities for social activities. Of course, the amount of spare time for socialising, geography, personality and gender all influence friendship size, but we also know that at least some of these factors, notably gender, also correlate with mentalising skills. Our study finds there is a link between the ability to read how other people think and social network size.'

Professor Dunbar's research was funded by the British Academy Centenary Research Project and by the British Academy Research Professorship. His research has already examined the different brain sizes of different species, but this study looks at the differences within species. Professor Dunbar published a paper last year, which found that people living near to the Poles needed larger brains for visual processing because of the dimmer light conditions.

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Teens: Power to Resist Blooms in Brain

Teens: Power to Resist Blooms in Brain

  9:55:00 AM    Science Lover

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Just when children are faced with intensifying peer pressure to misbehave, regions of the brain are actually blossoming in a way that heighten the ability to resist risky behavior, report researchers at three West Coast institutions.

Researchers compared the fMRI results from age 10 to age 13, finding that activity increased significantly in the ventral striatum and the ventral medial portion of the prefrontal cortex over this three-year period. (Credit: Image courtesy of University of Oregon)

The findings -- detailed in the March 10 issue of the journal Neuron -- may give parents a sigh of relief regarding their kids as they enter adolescence and pay more attention to their friends. However, the research provides scientists with basic insight about the brain's wiring, rather than direct clinical relevance for now.

In the study, 24 girls and 14 boys from ethnically and socioeconomically diverse backgrounds underwent functional magnetic resonance imaging (fMRI) scans twice, at ages 10 and 13, the latter representing when children have moved into early adolescence. Each time, they were presented with photos of faces making neutral, angry, fearful, happy and sad emotional expressions.

Non-invasive fMRI, when focused on the brain, measures blood flow changes using a magnetic field and radio frequency pulses, producing detailed images that provide scientists with information about brain activity or help medical staff diagnose disease.

Researchers compared the fMRI results from age 10 to age 13, finding that activity increased significantly in the ventral striatum and the ventral medial portion of the prefrontal cortex over this three-year period. In addition to the scans, the researchers considered the children's self-reports on their ability to resist peer influences and engagement in risky or delinquent behavior.

The most enhanced response occurred in the ventral striatum, a brain region most frequently associated with reward-related processing. Over time, increases in brain activity there correlated with increases in children's resistance to peer influence.

"This is a complex point, because people tend to think of adolescence as the time when teenagers are really susceptible to peer pressure," said Jennifer H. Pfeifer, professor of psychology at the University of Oregon. "That is the case, but in addition to that added susceptibility they are also improving their ability to resist it. It's just that peer pressure is increasing because they spend a lot more time with peers during this time and less time with family. So it is a good thing that resistance to such influences is actually strengthening in their brains."

This study, which researchers believed to be the first to report longitudinal fMRI findings about changes in the way the brain processes emotion during this critical time of brain development, appears to fit into a growing body of evidence that ventral striatum development during early adolescence is critical to emotional regulation carried out by the brain's prefrontal circuitry, the researchers concluded.

"This is basic research that hopefully is laying the foundation for future studies with even more clinical relevance," said Pfeifer, director of the Developmental Social Neuroscience Lab. "We really have a lot to learn about how the brain responds to really basic emotional stimuli across development."

There was a surprise finding that deserves more study, though, Pfeifer said. Responses in the amygdala -- a small almond-shaped mass centrally located deep in the brain -- showed significant increases during this period only to the sad faces.

The amygdala plays a major role in emotional reactivity and indexing the salience of things in the environment. It's possible, Pfeifer said, that this response to sad faces could somehow be tied to the emergence of depression, especially in girls.

"This response in the amygdala raises questions we hope to pursue," she said. "The span from age 9 to 13 is critical in pubertal development. How do individual differences apply here? Identifying this response to 'sadness' in the amygdala opens the door to thinking about how changes in emotional reactivity might be related to the increase in depression that we see as kids enter puberty. Rates of depression are particularly enhanced for teen girls. Is this increased response to sad faces somehow part of that?"

Based on results of the new study, she added, "I think what we know about the ventral striatum may be poised to undergo a transformation over the next several years."

Six co-authors on the study with Pfeifer were: Carrie L. Masten of the Center for Mind and Brain at the University of California, Davis; William E. Moore III and Tasha M. Oswald, both doctoral students in the UO psychology department; John C. Mazziotta of the Ahmanson-Lovelace Brain Mapping Center at the University of California, Los Angeles; and Marco Iacoboni and Mirella Dapretto, both colleagues of Mazziotta and also with the FPR-UCLA Center for Culture, Brain, and Development at UCLA.

The National Center for Research Resources of the National Institutes of Health supported the research through three grants to the collaborating scientists.

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Brain Matter Linked to Introspective Thoughts Structure of Prefrontal Cortex Helps Humans Think About One's Own Thinking

Brain Matter Linked to Introspective Thoughts Structure of Prefrontal Cortex Helps Humans Think About One's Own Thinking

  9:51:00 AM    Science Lover

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A specific region of the brain appears to be larger in individuals who are good at turning their thoughts inward and reflecting upon their decisions, according to new research published in the journal Science. This act of introspection -- or "thinking about your thinking" -- is a key aspect of human consciousness, though scientists have noted plenty of variation in peoples' abilities to introspect.

Views of inflated cortical surface showing areas of brain gray matter correlating with introspective accuracy. (Credit: Image © Science/AAAS)

The new study will be published in the 17 September issue of the journal Science. Science is published by AAAS, the nonprofit science society.

In light of their findings, this team of researchers, led by Prof. Geraint Rees from University College London, suggests that the volume of gray matter in the anterior prefrontal cortex of the brain, which lies right behind our eyes, is a strong indicator of a person's introspective ability. Furthermore, they say the structure of white matter connected to this area is also linked to this process of introspection.

It remains unclear, however, how this relationship between introspection and the two different types of brain matter really works. These findings do not necessarily mean that individuals with greater volume of gray matter in that region of the brain have experienced -- or will experience -- more introspective thoughts than other people. But, they do establish a correlation between the structure of gray and white matter in the prefrontal cortex and the various levels of introspection that individuals may experience.

In the future, the discovery may help scientists understand how certain brain injuries affect an individual's ability to reflect upon their own thoughts and actions. With such an understanding, it may eventually be possible to tailor appropriate treatments to patients, such as stroke victims or those with serious brain trauma, who may not even understand their own conditions.

"Take the example of two patients with mental illness -- one who is aware of their illness and one who is not," said one of the study's authors, Stephen Fleming from University College London. "The first person is likely to take their medication, but the second is less likely. If we understand self-awareness at the neurological level, then perhaps we can also adapt treatments and develop training strategies for these patients."

This new study was born from collaboration between Rees' group, which investigates consciousness, and another group at University College London led by Prof. Ray Dolan, which studies decision-making. Fleming, together with co-author Rimona Weil, designed an experiment to measure both an individual's performance at a task, as well as how confident that individual felt about his or her decisions during the task. By taking note of how accurately the study's participants were able to judge their own decision-making, the researchers were able to gain insight into the participants' introspective abilities.

To begin, Fleming and Weil recruited 32 healthy human participants and showed them two screens, each containing six patterned patches. One of the screens, however, contained a single patch that was brighter than all the rest. The researchers asked the participants to identify which screen contained the brighter patch, and then to rate how confident they felt about their final answer. After the experiment, participants' brains were scanned using magnetic resonance imaging, or MRI.

Fleming and the researchers designed the task to be difficult, so that participants were never completely sure if their answer was correct. They reasoned that participants who are good at introspection would be confident after making correct decisions about the patch, and less confident when they were incorrect about the patch. By adjusting the task, the researchers ensured all of the participants' decision-making abilities were on par with each others' -- only the participants' knowledge of their own decision-making abilities differed.

"It's like that show, 'Who Wants to Be a Millionaire?'" said Weil. "An introspective contestant will go with his or her final answer when they are quite sure of it, and perhaps phone a friend when they are unsure. But, a contestant who is less introspective would not be as effective at judging how likely their answer is to be correct."

So, although each participant performed equally well at the task, their introspective abilities did vary considerably, the researchers confirmed. By comparing the MRI scans of each participant's brain, they could then identify a correlation between introspective ability and the structure of a small area of the prefrontal cortex. An individual's meta-cognitive, or "higher-thinking," abilities were significantly correlated with the amount of gray matter in the right anterior prefrontal cortex and the structure of neighboring white matter, Rees and his team found.

These findings, however, could reflect the innate differences in our anatomy, or alternatively, the physical effects of experience and learning on the brain. The latter possibility raises the exciting prospect that there may be a way to "train" meta-cognitive abilities by exploiting the malleable nature of these regions of prefrontal cortex. But, more research is needed to explore the mental computations behind introspection -- and then to link these computations to actual biological processes.

"We want to know why we are aware of some mental processes while others proceed in the absence of consciousness," said Fleming. "There may be different levels of consciousness, ranging from simply having an experience, to reflecting upon that experience. Introspection is on the higher end of this spectrum -- by measuring this process and relating it to the brain we hope to gain insight into the biology of conscious thought."

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How We Know A Dog Is A Dog: Concept Acquisition In The Human Brain

How We Know A Dog Is A Dog: Concept Acquisition In The Human Brain

  10:35:00 AM    Science Lover

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A new study explores how our brains synthesize concepts that allow us to organize and comprehend the world. The research, published by Cell Press in the September 24th issue of the journal Neuron, uses behavioral and neuroimaging techniques to track how conceptual knowledge emerges in the human brain and guides decision making.

Although two dogs can look very different, the human brain recognizes them as particular instances of the concept of a dog. (Credit: iStockphoto/Annette Wiechmann)







The ability to use prior knowledge when dealing with new situations is a defining characteristic of human intelligence. This is made possible through the use of concepts, which are formed by abstracting away the common essence from multiple distinct but related entities. "Although a Poodle and a Golden Retriever look very different from each other, we can easily appreciate their similar attributes because they can be recognized as instances of a particular concept, in this case a dog," explains lead study author, Dr. Dharshan Kumaran from the Wellcome Trust Centre for Neuroimaging at University College London.

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Why We Learn More From Our Successes Than Our Failures

Why We Learn More From Our Successes Than Our Failures

  9:10:00 PM    Science Lover

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If you've ever felt doomed to repeat your mistakes, researchers at MIT's Picower Institute for Learning and Memory may have explained why: Brain cells may only learn from experience when we do something right and not when we fail.

Given different images as cues, monkeys were trained to look right or left for rewards.
MIT neuroscientists found that neurons responded differently following correct and
incorrect responses, with correct responses setting up the brain for additional successes.
(Credit: Courtesy / Earl Miller)

In the July 30 issue of the journal Neuron, Earl K. Miller, the Picower Professor of Neuroscience, and MIT colleagues Mark Histed and Anitha Pasupathy have created for the first time a unique snapshot of the learning process that shows how single cells change their responses in real time as a result of information about what is the right action and what is the wrong one.

"We have shown that brain cells keep track of whether recent behaviors were successful or not," Miller said. Furthermore, when a behavior was successful, cells became more finely tuned to what the animal was learning. After a failure, there was little or no change in the brain — nor was there any improvement in behavior.

The study sheds light on the neural mechanisms linking environmental feedback to neural plasticity — the brain's ability to change in response to experience. It has implications for understanding how we learn, and understanding and treating learning disorders.

Rewarding success

Monkeys were given the task of looking at two alternating images on a computer screen. For one picture, the animal was rewarded when it shifted its gaze to the right; for another picture it was supposed to look left. The monkeys used trial and error to figure out which images cued which movements.

The researchers found that whether the animals' answers were right or wrong, signals within certain parts of their brains "resonated" with the repercussions of their answers for several seconds. The neural activity following a correct answer and a reward helped the monkeys do better on the trial that popped up a few seconds later.

"If the monkey just got a correct answer, a signal lingered in its brain that said, 'You did the right thing.' Right after a correct answer, neurons processed information more sharply and effectively, and the monkey was more likely to get the next answer correct as well," Miller said, "But after an error there was no improvement. In other words, only after successes, not failures, did brain processing and the monkeys' behavior improve."

Split-second influence

The prefrontal cortex orchestrates thoughts and actions in accordance with internal goals while the basal ganglia are associated with motor control, cognition and emotions. This work shows that these two brain areas, long suspected to play key roles in learning and memory, have full information available to them to do all the neural computations necessary for learning.

The prefrontal cortex and basal ganglia, extensively connected with each other and with the rest of the brain, are thought to help us learn abstract associations by generating brief neural signals when a response is correct or incorrect. But researchers never understood how this transient activity, which fades in less than a second, influenced actions that occurred later.

In this study, the researchers found activity in many neurons within both brain regions that reflected the delivery or withholding of a reward lasted for several seconds, until the next trial. Single neurons in both areas conveyed strong, sustained outcome information for four to six seconds, spanning the entire time frame between trials.

Response selectivity was stronger on a given trial if the previous trial had been rewarded and weaker if the previous trial was an error. This occurred whether the animal was just learning the association or was already good at it.

After a correct response, the electrical impulses coming from neurons in each of the brain areas was more robust and conveyed more information. "The signal-to-noise ratio improved in both brain regions," Miller said. "The heightened response led to them being more likely to get the next trial correct, too. This explains on a neural level why we seem to learn more from our successes than our failures."

In addition to Miller, authors include former MIT graduate student Mark H. Histed, now a postdoctoral fellow at Harvard Medical School, and former postdoctoral fellow Anitha Pasupathy, now an assistant professor at the University of Washington.

This work is supported by National Institute of Neurological Disorders and Stroke and the Tourette's Syndrome Association.

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