Posts Tagged Prefrontal cortex

Stress, Depression Reduce Brain Volume Thanks to Genetic ‘Switch’


Stress, Depression Reduce Brain Volume Thanks to Genetic 'Switch' Scientists have known that stress and depression can cause the brain to retract or lose volume, a condition associated with both emotional and cognitive impairment. Now, a new study discovers why this occurs.

Yale scientists have found that the deactivation of a single genetic switch can instigate a cascading loss of brain connections in humans and depression in animal models.

Researchers say the genetic switch, known as a transcription factor, represses the expression of several genes that are necessary for the formation of synaptic connections between brain cells. The loss of connections, in turn, can contribute to loss of brain mass in the prefrontal cortex, say the scientists.

“We wanted to test the idea that stress causes a loss of brain synapses in humans,” said senior author Ronald Duman, Ph.D. “We show that circuits normally involved in emotion, as well as cognition, are disrupted when this single transcription factor is activated.”

In the study, the research team analyzed tissue of depressed and non-depressed patients donated from a brain bank and looked for different patterns of gene activation.

The brains of patients who had been depressed exhibited lower levels of expression in genes that are required for the function and structure of brain synapses.

Lead author and postdoctoral researcher H.J. Kang, Ph.D., discovered that at least five of these genes could be regulated by a single transcription factor called GATA1.

When the transcription factor was activated in animal models, rodents exhibited depressive-like symptoms, suggesting GATA1 plays a role not only in the loss of connections between neurons but also in symptoms of depression.

This finding of genetic variations in GATA1 may help researchers identify people at high risk for major depression or sensitivity to stress.

“We hope that by enhancing synaptic connections, either with novel medications or behavioral therapy, we can develop more effective antidepressant therapies,” Duman said.

Source: Yale University

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Stress may delay brain development in early years


There has been a lot of work in animals linking both acute and chronic stress to changes in a part of the brain called the prefrontal cortex, which is involved in complex cognitive abilities like holding on to important information for quick recall and use,” says Jamie Hanson, a UW-Madison psychology graduate student. “We have now found similar associations in humans, and found that more exposure to stress is related to more issues with certain kinds of cognitive processes.”

Children who had experienced more intense and lasting stressful events in their lives posted lower scores on tests of what the researchers refer to as spatial working memory. They had more trouble navigating tests of short-term memory such as finding a token in a series of boxes, according to the study, which will be published in the June 6 issue of the Journal of Neuroscience.

Brain scans revealed that the anterior cingulate, a portion of the prefrontal cortex believed to play key roles in spatial working memory, takes up less space in children with greater exposure to very stressful situations.

“These are subtle differences, but differences related to important cognitive abilities” Hanson says.

But they maybe not irreversible differences.

“We’re not trying to argue that stress permanently scars your brain. We don’t know if and how it is that stress affects the brain,” Hanson says. “We only have a snapshot — one MRI scan of each subject — and at this point we don’t understand whether this is just a delay in development or a lasting difference. It could be that, because the brains is very plastic, very able to change, that children who have experienced a great deal of stress catch up in these areas.”

The researchers determined stress levels through interviews with children ages 9 to 14 and their parents. The research team, which included UW-Madison psychology professors Richard Davidson and Seth Pollak and their labs, collected expansive biographies of stressful events from slight to severe.

“Instead of focusing in on one specific type of stress, we tried to look at a range of stressors,” Hanson says. “We wanted to know as much as we could, and then use all this information to later to get an idea of how challenging and chronic and intense each experience was for the child.”

Interestingly, there was little correlation between cumulative life stress and age. That is, children who had several more years of life in which to experience stressful episodes were no more likely than their younger peers to have accumulated a length stress resume. Puberty, on the other hand, typically went hand-in-hand with heavier doses of stress.

The researchers, whose work was funded by the National Institutes of Health, also took note of changes in brain tissue known as white matter and gray matter. In the important brain areas that varied in volume with stress, the white and gray matter volumes were lower in tandem.

White matter, Hanson explained, is like the long-distance wiring of the brain. It connects separated parts of the brain so that they can share information. Gray matter “does the math,” Hanson says. “It takes care of the processing, using the information that gets shared along the white matter connections.”

Gray matter early in development appears to enable flexibility; children can play and excel at many different activities. But as kids age and specialize, gray matter thins. It begins to be “pruned” after puberty, while the amount of white matter grows into adulthood.

“For both gray and white matter, we actually see smaller volumes associated with high stress,” Hanson says. “Those kinds of effects across different kinds of tissue, those are the things we would like to study over longer periods of time. Understanding how these areas change can give you a better picture of whether this is just a delay in development or more lasting.”

More study could also show the researchers how to help children who have experienced an inordinate amount of stress.

“There are groups around the country doing working memory interventions to try to train or retrain people on this particular cognitive ability and improve performance,” Hanson says. “Understanding if and how stress affects these processes could help us know whether there may be similar interventions that could aid children living in stressful conditions, and how this may affect the brain.”

via Stress may delay brain development in early years.

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Number of Friendships Linked to Brain Size


Number of Friendships Linked to Brain Size | Psych Central News

Number of Friendships Linked to Brain Size
By TRACI PEDERSEN Associate News Editor
Reviewed by John M. Grohol, Psy.D. on March 26, 2012
If you have a lot of friends, then you most likely have a bigger orbital prefrontal cortex — a brain region found just above the eyes — according to a new study, part of the British Academy Centenary “Lucy to Language” project.

The research shows that in order to maintain several friendships (not acquaintances), it is necessary to use what social scientists refer to as “mentalizing” or “mind-reading” — the capacity to understand what another person is thinking.  This skill is crucial in handling a complex social world, including the ability to hold a conversation.

This study is the first to suggest that proficiency in these skills is linked to the size of key regions of the brain, particularly the frontal lobe.

“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 mentalizing 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,” said psychologist Dr. Joanne Powell from the University of Liverpool.

For the study, researchers used an MRI to scan the brains of 40 volunteers in order to measure the size of the prefrontal cortex, the region used in high-level thinking. Participants were then asked to list 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 mentalizing.

‘We found that individuals who had more friends did better on mentalizing tasks and had more neural volume in the orbital frontal cortex, the part of the forebrain immediately above the eyes,” said Robin Dunbar, Ph.D.,  of the University of Oxford and the Institute of Cognitive and Evolutionary Anthropology.

“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.”

“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 socializing, geography, personality and gender all influence friendship size, but we also know that at least some of these factors, notably gender, also correlate with mentalizing skills.

“Our study finds there is a link between the ability to read how other people think and social network size,” added Dunbar.

The study is published in the journal Proceedings of the Royal Society B.

Source:  University of Oxford

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