Friday, September 7, 2012

Stress may harm brain - but it recovers

Stress may harm brain - but it recovers
We all know stress is bad for you, but just how bad?

It would be unethical to intentionally subject people to extreme psychological duress in the name of science. But ongoing military operations offer opportunities to see what happens to people exposed to stressful situations.

Researchers in the Netherlands found the brains of soldiers who go into combat show impairment in function and structure upon returning, but that these effects largely go away over time.

The study
A new study published in the journal Proceedings of the National Academy of Sciences looked at 33 healthy Dutch soldiers deployed to Afghanistan for four months. It was the first military deployment for all of them, part of a NATO peacekeeping operation.

Researchers compared these participants to 26 soldiers who were never deployed.

The soldiers who were deployed experienced armed combat and exposure to enemy fire, as well as other common combat stressors. But this did not appear to aggravate stress symptoms; researchers did not find significant differences in post-traumatic stress disorder, anxiety and mood scores between the deployed and non-deployed groups.

But despite no apparent trends in psychological symptoms, the two groups of participants did display marked brain differences.

The combat group showed reduced functioning in the midbrain, as well as structural differences in that area. These soldiers who had gone to Afghanistan tended to perform worse on cognitive tests than those who were not deployed.


Those effects were seen less than two months after the soldiers returned from combat.

But a year and a half later, researchers found that the soldiers who had been deployed had, on average, returned to normal with respect to both brain structure and cognitive performance.

The combat group still showed some brain impairment: Imaging tests showed that there was less connectivity between particular brain regions among these soldiers than those who had not been deployed.

"Although there are some subtle changes, it doesn't really directly translate into impaired performance," said Guido van Wingen of the Brain Imaging Center in Amsterdam, who was the lead author of the study.

Although cognitive performance may suffer, a different brain function may be enhanced in soldiers with recent combat experience: vigilance. Previous research from van Wingen's group shows that the amygdala, a part of the brain important for detecting potential danger, has heightened activity in soldiers who have returned recently from combat. That effect also normalizes over time.

Study drawbacks

The sample size of the study began small, and got smaller over time. Nine people from the combat group and nine people from the non-deployed group did not complete the long-term follow-up.

Also, this study deals only with people from the Netherlands.


The research is too preliminary to make recommendations, van Wingen said.

But it makes sense that soldiers would benefit from time to recuperate in between deployments, so that the brain can re-adapt to a non-combat situation, he said.

Bottom line

"What the results collectively show is the brain is able to restore (itself) from the adverse effects of stress, if you give it at least enough time," van Wingen said.

Revenge of the Lizard Brain

There’s a scene in Fear & Loathing in Las Vegas in which the writer, high out of his mind on hallucinogens, watches a roomful of casino patrons transform into giant lizards and lunge at each other in bloody combat. Under the veneer of civilization, the scene suggests, we’re all still reptiles, just waiting for the moment to strike.

Strange as it seems, this drug-fueled vision reflects a biological theory that, back in the ‘60s, looked like it might be gaining some traction: Paul MacLean’s infamous “Triune Brain” theory, whose basic idea is that every human brain contains three independent competing minds – the reptile, the early mammal, and the modern primate.

Like the Fear & Loathing scene, the Triune Brain idea holds a certain allegorical appeal: The primal lizard – a sort of ancestral trickster god – lurking within each of us. But today, writers and speakers are dredging up the corpse of this old theory, dressing it with some smart-sounding jargon, and parading it around as if it’s scientific fact. This isn’t just late-night-radio fringe stuff, either: it’s showing up at TED and in Forbes.

To understand what it is, exactly, that these people are claiming, it helps to know a few key points about MacLean’s – shall we say – unique personal views on neuroanatomy. Take, for instance, the basal ganglia – that bundle of neural structures near the base of the forebrain. They’re crucial for learning and reinforcing habits, like nail-biting and toothbrushing. Back in the 1960s, biologists thought the forebrains of reptiles and birds were mainly composed of basal ganglia (they aren’t), so MacLean decided to group these structures, along with the brainstem, under the label “reptilian complex.” This “R-complex,” MacLean claimed, was responsible for the “aggression, dominance, territoriality, and ritual displays” of our distant reptilian ancestors.
MacLean also noticed that some of the more complex neural structures folded around the basal ganglia – such as the amygdala, the hypothalamus and the cingulate cortex – play central roles in emotions like disgust, nervousness, doubt and so on. So he figured these brain areas must’ve arisen in the earliest mammals to cope with tasks like family bonding and child-rearing. He gathered them under a heading and slapped the label “paleomammalian complex” on it.

Finally, MacLean noted that the neocortex – the uppermost, outermost layer of the brain – is found only in mammals, and is linked with “high-level cognitive abilities” like abstract planning, tool-making, language, and self-awareness. Thus, he termed it the “neomammalian complex.”

But MacLean wasn’t done. He went on to hypothesize that these three “complexes” not only represented three distinct stages of brain evolution, but remained three separate, semi-independent brains, “[each] with its own special intelligence, its own subjectivity, its own sense of time and space and its own memory.”  MacLean was saying, in other words, that every human brain contains three independent subjective consciousnesses.

All in all, a truly mind-blowing trip to lay on your friends. Problem is, MacLean’s pet hypothesis doesn’t hold up under scrutiny. For example:
  1. Basal ganglia are found in the brains of the earliest jawed fish, which means MacLean’s “reptile complex” originated long before the first tetrapods wriggled onto land.
  1. The earliest mammals already had well-formed neocortices, which means at least some “high-level cognitive abilities” predate mammals altogether.
  1. Many reptiles exhibit “paleomammalian” behaviors such as familial bonding and child-rearing, and many birds exhibit “neomammalian” skills like tool-making, verbal comprehension and dialect development.
  1. In functional terms, a human brain doesn’t behave like a series of separate “complexes,” but as a unified whole. Some neural networks do inhibit others – but the shapes of those networks have nothing to do with “reptilian” or “mammalian” layers.
How is it, then, that modern authors as educated as Seth Godin and Rick Hanson (among others) are writing entire essays that present “the lizard brain” as well-documented scientific fact? How does Godin keep a straight face onstage as he tells us that “the lizard is a physical part of your brain” and that “the reason we call wild animals ‘wild’ is because they have lizard brains”?

It’s because the idea makes a weird kind of intuitive sense. We’re bundles of instincts and inhibitions and desires that don’t fit neatly together. It’d be comforting, in a way, if we could pin those conflicts on little lizard brains – just name those ancient demons and drive ‘em out, like we did in simpler times.

Whether we like it or not, though, the lizard is simply us. Every habit and hangup, every dread and desire in our minds is dependent on neural pathways that were once laid down by our personal experiences. Like every other organism on earth, we carry the history of a long, successful lineage in our genetic and biological makeup. The question of what to do with those resources, though, isn’t predetermined by the past. It’s up to you.

Brain Blocks Information to Form Memories

Neuronal Processing of Inhibition and Excitation in smallest nerve cell prolongations. Schematic representation of a tiny nerve cell prolongation (dendrite) that processes exhibitory and inhibitory signals. Image: C. MüllerEvery activity in the brain involves the transfer of signals between neurons. Frequently, as many as one thousand signals rain down on a single neuron simultaneously. To ensure that precise signals are delivered, the brain possesses a sophisticated inhibitory system. Stefan Remy and colleagues at the German Center for Neurodegenerative Diseases and the Univ. Bonn have illuminated how this system works. “The system acts like a filter, only letting the most important impulses pass,” explains Remy. “This produces the targeted neuronal patterns that are indispensible for long-term memory storage.”

How does this refined control system work? How can inhibitory signals produce precise output signals? This was the question investigated by Remy and his colleagues. Scientists have known for some time that this inhibitory system is crucial for the learning process. For instance, newest research has shown that this system breaks down in Alzheimer’s patients. Remy and his team investigated the nerve cells of the hippocampus, a region of the brain that plays a crucial role in memory formation.

The information we learn or remember is processed in the brain through nerve impulses. Incoming signals enter the cell as excitatory signals. Here, they are processed via branched structures, known as dendrites, and are sent selectively to neighboring neurons. The dendrites in this brain region serve as efficient amplifiers for synchronous signals.

“We were able to show that in specific dendrites, the ‘strong’ dendrites, clustered signals are amplified very well. ‘Weak’ dendrites only transmit signals in certain phases,” says Christina Müller, postdoctoral student in Remy’s working group and the lead author of the study to appear in Neuron. Dendrites are excitable to differing degrees. “Strong” dendrites transmit synchronous excitatory signals precisely and very reliably. They can resist any inhibition. Thus ensures specific signals, perhaps most relevant for learning and memory, are reliably transmitted. This results in defined patterns of activity that are repeated regularly, creating simultaneous excitation and a combination of specific cell groups (assemblies).

“It is assumed that this coactivation of cell assemblies is a cellular correlate for learning,” says Müller. If associations are to be stored in long-term memory, certain neuronal groups must be precisely and repeatedly activated in the same order. These activity patterns are enabled by the inhibitory system. It explains why the absence of this system in Alzheimer’s patients has such dramatic consequences. Without it, the storage of associations in long-term memory cannot take place.

Signals that are received via “weak” dendrites can only be passed forward during phases of weak inhibition. They can however be transformed into “strong” dendrites during this process. According to Remy and his colleagues, only then can these dendrites provide precise signal transmission. Scientists call this “intrinsic plasticity.”

“This makes sense. Because this is how neuronal networks can be coupled with each other and the coupling made permanent,” explains Remy. “This is a totally new learning mechanism. Here the change does not take place at the synapse – where it’s already been observed – but at the dendrite.” This mechanism mostly takes place during phases of heightened activity, such as when we experience something new.
The findings of Remy and his colleagues represent an important step toward better understanding the mechanisms of learning and memory.

Green tea found to boost brain power; Also possible weapon against cancer, gum disease and glaucoma

In addition to being heart healthy and a possible weapon against cancer, gum disease and glaucoma, new evidence shows that green tea could also be a powerful brain booster.
The research out of China is the latest study to tout the health benefits of this Asian tonic, consumed mainly in Japan and China and now ubiquitous around the Western world.
In a study published in Molecular Nutrition & Food Research and released this week, a team of Chinese researchers showed that an organic chemical found in green tea, epigallocatechin-3 gallate or EGCG, could improve memory and spatial learning by boosting the generation of brain cells, a process known as neurogenesis.
The compound EGCG is already known for its antioxidant properties. But in the Chinese study, EGCG was also shown to be beneficial against age-related degenerative diseases with particular impact on the hippocampus, the part of the brain which processes information from short-term to long-term memory, scientists said.
For their study, researchers ran tests on two groups of mice, one of which was fed EGCG, and the other acting as a control group.
The mice were then trained for several days to find a visible and an invisible platform within a maze.
What researchers found was that the mice treated with the green tea compound required less time to find the hidden platform compared to their counterparts, showing that EGCG can enhance learning and memory by improving object recognition and spatial memory, they said.
"We have shown that the organic chemical EGCG acts directly to increase the production of neural progenitor cells, both in glass tests and in mice," said lead author Yun Bai. "This helps us to understand the potential for EGCG, and green tea which contains it, to help combat degenerative diseases and memory loss."
But while green tea may tout antioxidant properties, a large-scale study out of Japan found, after analyzing 54,000 women, that the drink does little to protect against one particular kind of cancer -- breast cancer.

Brain Scans Help Predict Treatment For Social Anxiety Disorder

Brain scans of patients with social anxiety disorder can help determine if cognitive behavioral therapy (CBT) could be an effective treatment option, suggests researchers from MIT, Boston University (BU), and Massachusetts General Hospital (MGH) in the Archives of General Psychiatry.

Either CBT or medications are normally used to treat social anxiety, but scientists have not been able to identify which of these treatments will suit a particular individual best.

By looking at photos of faces and measuring brain activity, the usefulness of therapy could be determined before the sessions even start, according to the team.

With about 15 million people in the United States struggling with the disorder, authors believe these findings will help doctors decide which treatment is right for each patient.

"Our vision is that some of these measures might direct individuals to treatments that are more likely to work for them," said John Gabrieli, lead author, the Grover M. Hermann Professor of Brain and Cognitive Sciences at MIT, and a member of the McGovern Institute for Brain Research.

Choosing The Right Treatment

CBT is known for changing the thought and behavior patterns that give the sufferer anxiety, such as feelings of intense fear in social settings that impair their ability to act normally. Some patients have anxiety because they think that others are watching them, however, the therapy shows that their beliefs are false and no one is judging them.

The current study is part of a larger one that MGH and BU conducted recently on cognitive behavioral therapy for social anxiety.

Gabrieli explained:

"This was a chance to ask if these brain measures, taken before treatment, would be informative in ways above and beyond what physicians can measure now, and determine who would be responsive to this treatment."
Although some patients find the idea of taking pills easier than going to therapy, it is not an effective method of treatment. Some doctors, on the other hand, are currently making decisions about treatment based on what their patient's insurance covers or because of potential drug side effects.

"From a science perspective there's very little evidence about which treatment is optimal for a person," Gabrieli commented.

In order to image patients' brains before and after treatment, functional magnetic resonance imaging (fMRI) was used. Imaging has never before been used as a way to predict a patient's reactions to a certain treatment, although some imaging studies have shown brain differences between patients with nueropyschiatric disorders and their healthy counterparts.

Measuring Differences in Brain Activity

Experts in the new study had subjects look at images of angry or neutral faces, in order to identify differences in brain activity as they observed. Social anxiety levels were tested after undergoing 12 weeks of CBT.

Results showed that those who benefited the most from therapy were the individuals who had shown a greater difference in activity in high-level visual processing areas during the face-response task.

It is unclear why activity in brain regions involved with visual processing would be a good indicator of treatment outcomes, according to Gabrieli. He believes it could be because the patients who received more benefits were those whose brains were already adept at separating different types of experiences.

The authors are carrying out further research to determine if brain scans can predict differences in response between cognitive behavioral therapy and drug treatments.

Gabrieli concluded:

"Right now, all by itself, we're just giving somebody encouraging or discouraging news about the likely outcome of therapy. The really valuable thing would be if it turns out to be differentially sensitive to different treatment choices."

Fatty food might cause brain damage

Fatty foods can destroy neurons in a part of the brain that controls energy balance and appetite, according to new research.

Brain damage caused by fatty food might be one reason why people who habitually over-eat find it so hard to lose weight, scientists have said.
New research suggests that saturated fat can destroy neurons in a part of the brain that controls energy balance and appetite.
Researchers found changes to vital genes and proteins in the brains of mice fed a high fat diet. The effects in the hypothalamus - the brain's energy centre - indicated the kind of damage normally caused by inflammation and blood clot strokes.
Lead scientist Lynda Williams, from the University of Aberdeen Rowett Institute, said: "These changes may underlie the breakdown of energy centres in the brain and may explain why its so difficult for obese people to maintain weight loss from dieting.
"Our results indicate that a high fat diet can damage the areas of the brain that control energy balance and perpetuate the development of obesity.
"High fat and high sugar foods are energy dense foods which are highly palatable and they are very easy to over-eat. Our findings may also explain why some overweight people find it difficult to diet and why weight loss after dieting is so difficult to maintain. We now plan to carry out further studies that will look at whether these effects are reversible."
She pointed out that brain scan studies in the US had shown signs of hypothalamus damage in obese individuals, suggesting that the effects seen in mice may also occur in humans. The hypothalamus is a small area at the base of the brain that contains neurons which govern energy expenditure and appetite.
"This control breaks down in obesity - the system appears not to work - and we don't really know why this happens," said Dr Williams, speaking at the British Science Festival at the University of Aberdeen.
"In our study we found that genes and proteins change in response to a high fat diet and that these changes are normally associated with damage to the brain, indicating that damage had occurred in the hypothalamus in mice that ate a diet high in saturated fat."
Dr Williams acknowledged the effects might be exaggerated in mice whose diet was drastically altered so they obtained 60% of their energy from saturated fat. The results did not mean people having the occasional unhealthy treat risked damaging their brains, she said.