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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Scientists Wrest Partial Control of a Memory

Scientists Wrest Partial Control of a Memory

  1:53:00 AM    Science Lover

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Scripps Research Institute scientists and their colleagues have successfully harnessed neurons in mouse brains, allowing them to at least partially control a specific memory. Though just an initial step, the researchers hope such work will eventually lead to better understanding of how memories form in the brain, and possibly even to ways to weaken harmful thoughts for those with conditions such as schizophrenia and post traumatic stress disorder.

Mouse. Scripps Research Institute scientists 
and their colleagues have successfully 
harnessed neurons in mouse brains, allowing 
them to at least partially control a specific 
memory. (Credit: © fergregory / Fotolia)

The results are reported in the March 23, 2012 issue of the journal Science.

Researchers have known for decades that stimulating various regions of the brain can trigger behaviors and even memories. But understanding the way these brain functions develop and occur normally -- effectively how we become who we are -- has been a much more complex goal.

"The question we're ultimately interested in is: How does the activity of the brain represent the world?" said Scripps Research neuroscientist Mark Mayford, who led the new study. "Understanding all this will help us understand what goes wrong in situations where you have inappropriate perceptions. It can also tell us where the brain changes with learning."

On-Off Switches and a Hybrid Memory

As a first step toward that end, the team set out to manipulate specific memories by inserting two genes into mice. One gene produces receptors that researchers can chemically trigger to activate a neuron. They tied this gene to a natural gene that turns on only in active neurons, such as those involved in a particular memory as it forms, or as the memory is recalled. In other words, this technique allows the researchers to install on-off switches on only the neurons involved in the formation of specific memories.

For the study's main experiment, the team triggered the "on" switch in neurons active as mice were learning about a new environment, Box A, with distinct colors, smells and textures.

Next the team placed the mice in a second distinct environment -- Box B -- after giving them the chemical that would turn on the neurons associated with the memory for Box A. The researchers found the mice behaved as if they were forming a sort of hybrid memory that was part Box A and part Box B. The chemical switch needed to be turned on while the mice were in Box B for them to demonstrate signs of recognition. Alone neither being in Box B nor the chemical switch was effective in producing memory recall.

"We know from studies in both animals and humans that memories are not formed in isolation but are built up over years incorporating previously learned information," Mayford said. "This study suggests that one way the brain performs this feat is to use the activity pattern of nerve cells from old memories and merge this with the activity produced during a new learning session."

Future Manipulation of the Past

The team is now making progress toward more precise control that will allow the scientists to turn one memory on and off at will so effectively that a mouse will in fact perceive itself to be in Box A when it's in Box B.

Once the processes are better understood, Mayford has ideas about how researchers might eventually target the perception process through drug treatment to deal with certain mental diseases such as schizophrenia and post traumatic stress disorder. With such problems, patients' brains are producing false perceptions or disabling fears. But drug treatments might target the neurons involved when a patient thinks about such fear, to turn off the neurons involved and interfere with the disruptive thought patterns.

In addition to Mayford, other authors of the paper, "Generation of a Synthetic Memory Trace," are Aleena Garner, Sang Youl Hwang, and Karsten Baumgaertel from Scripps Research, David Rowland and Cliff Kentros from the University of Oregon, Eugene, and Bryan Roth from the University of North Carolina (UNC), Chapel Hill.

This work is supported by the National Institute of Mental Health, the National Institute on Drug Abuse, the California Institute for Regenerative Medicine, and the Michael Hooker Distinguished Chair in Pharmacology at UNC.

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Brain Imaging Study Finds Evidence of Basis for Caregiving Impulse

Brain Imaging Study Finds Evidence of Basis for Caregiving Impulse

  7:17:00 PM    Science Lover

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Distinct patterns of activity -- which may indicate a predisposition to care for infants-- appear in the brains of adults who view an image of an infant face -- even when the child is not theirs, according to a study by researchers at the National Institutes of Health and in Germany, Italy, and Japan.

Researchers have found that distinct patterns of activity --
which may indicate a predisposition to care for infants --
appear in the brains of adults who view an image of an
infant face -- even when the child is not theirs.
(Credit: © Jamey Ekins / Fotolia)

Seeing images of infant faces appeared to activate in the adult's brains circuits that reflect preparation for movement and speech as well as feelings of reward.

The findings raise the possibility that studying this activity will yield insights into care giving behavior, but also in cases of child neglect or abuse.

"These adults have no children of their own. Yet images of a baby's face triggered what we think might be a deeply embedded response to reach out and care for that child," said senior author Marc H. Bornstein, Ph.D., head of the Child and Family Research Section of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the NIH institute that collaborated on the study.

While the researchers recorded participants' brain activity, the participants did not speak or move. Yet their brain activity was typical of patterns preceding such actions as picking up or talking to an infant, the researchers explained. The activity pattern could represent a biological impulse that governs adults' interactions with small children.

From their study results, the researchers concluded that this pattern is specific to seeing human infants. The pattern did not appear when the participants looked at photos of adults or of animals -- even baby animals.

Along with Dr. Bornstein, the research was carried out by first author Andrea Caria, Ph.D., of the University of Tuebingen, in Germany; Paola Venuti of the Department of Cognitive Science of University of Trento in Italy; Gianluca Esposito of the RIKEN Brain Science Institute in Saitama, Japan; researchers from the Max Planck Institute for Biological Cybernetics and Eberhard Karls University, in Tuebingen, Germany.

Their findings appear in the journal NeuroImage.

To collect the data, the researchers showed seven men and nine women a series of images while recording their brain activity with a functional magnetic resonance imaging scanner. In the scanner, participants viewed images of puppy and kitten faces, full-grown dogs and cats, human infants and adults.

When the researchers compared the areas and strength of brain activity in response to each kind of image, they found that infant images evoked more activity than any of the other images in brain areas associated with three main functions:

• Premotor and preverbal activity -- The researchers documented increased activity in the premotor cortex and the supplemental motor area, which are regions of the brain directly under the crown of the head. These regions orchestrate brain impulses preceding speech and movement but before movement takes place.
• Facial recognition -- Activity in the fusiform gyrus -- on each side of the brain, about where the ears are -- is associated with processing of information about faces. Activity the researchers detected in the fusiform gyrus may indicate heightened attention to the movement and expressions on an infant's face, the researchers said.
• Emotion and reward -- Activity deep in the brain areas known as the insula and the cingulate cortex indicated emotional arousal, empathy, attachment and feelings linked to motivation and reward, the researchers said. Other studies have documented a similar pattern of activity in the brains of parents responding to their own infants.

Participants also rated how they felt when viewing adult and infant faces. They reported feeling more willing to approach, smile at, and communicate with an infant than an adult. They also recorded feeling happier when viewing images of infants.

Taken together, the researchers contend, the findings suggest a readiness to interact with infants that previously has been only inferred, and only from parents. Such brain activity in nonparents could indicate that the biological makeup of humans includes a mechanism to ensure that infants survive and receive the care they need to grow and develop.

However, signs of readiness to care for a child that appear in the brains of some or even most adults do not necessarily mean the same patterns will appear in the brains of all adults, Dr. Bornstein said. "It's equally important to investigate what's happening in the brains of those who have neglected or abused children," he said. "Additional studies could help us confirm and understand what appears to be a parenting instinct in adults, both when the instinct functions and when it fails to function."

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