Posts Tagged Brain Regions

Stress Changes Learning in the Brain


Stress Changes Learning in the BrainA new experiment from German scientists suggests stress invokes our brain to use different and more complex processes during learning.

In the study, cognitive psychologists Drs. Lars Schwabe and Oliver Wolf discovered that the presence or absence of stress is associated with use of different brain regions and different strategies in the learning process.

Stress appears to make the brain work harder and use a more complex approach when learning. Study findings are reported in the Journal of Neuroscience.

Researchers discovered that non-stressed individuals applied a deliberate learning strategy, while stressed subjects relied more on their gut feeling.

“These results demonstrate for the first time that stress has an influence on which of the different memory systems the brain turns on,” said Schwabe.

In the study researchers analyzed the data from 59 subjects. Two groups were assigned with one group asked to immerse one hand into ice-cold water for three minutes (while being observed by video surveillance).

As expected, this activity stressed the subjects with data collected and confirmed by hormone assays.

The other group was asked to immerse one of their hands in warm water. Then both the stressed and non-stressed individuals completed a task called weather prediction. The task involved having subjects look at playing cards with different symbols and then using the cards to predict which combinations of cards forecast rain and which sunshine.

Each combination of cards was associated with a certain probability of good or bad weather. People apply differently complex strategies in order to master the task.

During the weather prediction task, the researchers recorded the brain activity with MRI.

Researchers found that both stressed and non-stressed subjects learned to predict the weather according to the symbols. However, the way in which they learned the task varied.

Non-stressed participants focused on individual symbols and not on combinations of symbols. They consciously pursued a simple strategy.

The MRI data showed that they activated a brain region in the medial temporal lobe – the hippocampus, which is important for long-term memory.

Stressed subjects, on the other hand, applied a more complex strategy.

They made their decisions based on the combination of symbols. They did this, however, subconsciously, i.e. they were not able to formulate their strategy in words.

In this group of stress participants, brain scans showed that the so-called striatum in the mid-brain was activated — a brain region that is responsible for more unconscious learning.

“Stress interferes with conscious, purposeful learning, which is dependent upon the hippocampus,” concluded Schwabe. “So that makes the brain use other resources. In the case of stress, the striatum controls behavior — which saves the learning achievement.”

Source: Ruhr-University Bochum

Abstract of the brain with key photo by shutterstock.

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Alzheimer’s More Aggressive in Younger Elderly


Alzheimers More Aggressive in Younger Elderly New research shows that Alzheimer’s disease hits people in their 60s and 70s harder than people who are 80 years and older.

Researchers at the University of California, San Diego School of Medicine note that the greatest risk factor for Alzheimer’s is age. In fact, by the age of 85, the likelihood of developing the dreaded neurological disorder is roughly 50 percent, they say.

But in their study, they found that the “younger elderly” — those in their 60s and 70s — showed higher rates of cognitive decline and faster rates of tissue loss in brain regions that are vulnerable during the early stages of Alzheimer’s, according to Dominic Holland, Ph.D., a researcher in the Department of Neurosciences at UC San Diego and the study’s first author.

“Additionally cerebrospinal fluid biomarker levels indicate a greater disease burden in younger than in older individuals,” he said.

Holland and his colleagues, using imaging and biomarker data from participants in the Alzheimer’s Disease Neuroimaging Initiative, examined 723 people, ages 65 to 90 years, who were categorized as either cognitively normal, with mild cognitive impairment (an intermediate stage between normal, age-related cognitive decline and dementia) or suffering from full-blown Alzheimer’s disease (AD).

The findings have implications for diagnosing the disease — which currently afflicts an estimated 5.6 million Americans, a number expected to triple by 2050 — and efforts to find new treatments, the researchers said.

At present, there is no cure for Alzheimer’s and existing therapies do not slow or stop the disease’s progression.

A key feature in the diagnosis of Alzheimer’s is its “relentless progressive course,” Holland said.

“Patients typically show marked deterioration year after year. If older patients are not showing the same deterioration from one year to the next, doctors may be hesitant to diagnose AD, and thus these patients may not receive appropriate care, which can be very important for their quality of life.”

Holland said it’s not clear why the disease is more aggressive among the younger elderly.

“It may be that patients who show onset of dementia at an older age, and are declining slowly, have been declining at that rate for a long time,” added co-author Linda McEvoy, Ph.D., associate professor of radiology. “But because of cognitive reserve or other still-unknown factors that provide ‘resistance’ against brain damage, clinical symptoms do not manifest till later age.”

Another possibility is that older patients may be suffering from mixed dementia — a combination of Alzheimer’s and other neurological conditions, Holland said. These patients might withstand the effects of Alzheimer’s until other adverse factors, such as brain lesions caused by cerebrovascular disease, take hold. At that time, Alzheimer’s can only be definitively diagnosed by an autopsy, he said.

Clinical trials to find new treatments for the disease may be affected by the differing rates of progression, researchers said.

“Our results show that if clinical trials of candidate therapies predominately enroll older elderly, who show slower rates of change over time, the ability of a therapy to successfully slow disease progression may not be recognized, leading to failure of the clinical trial,” said Holland. “It’s critical to take into account age as a factor when enrolling subjects for AD clinical trials.”

While the obvious downside of the findings is that younger patients with Alzheimer’s lose more of their productive years, “the good news in all of this is that our results indicate those who survive into the later years before showing symptoms of AD will experience a less aggressive form of the disease,” Holland concluded.

The research appears online in the journal PLOS One.

Source: University of California, San Diego

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Stress Hormones Impede Healthy Behavioral Change


Stress Hormones Impede Healthy Behavioral ChangeFor many people, stress is the factor that unravels diets, exercise plans and other goal-directed tasks.

European researchers believe they have discovered why stressed persons are more likely to lapse back into old habits rather than follow a goal-directed agenda.

In a study, investigators determined stress hormones shut down the activity of brain regions for goal-directed behavior, yet do not affect the brain regions responsible for habitual behavior.

Researchers from the Ruhr-Universität in Germany, together with colleagues from the University Hospital Bergmannsheil, mimicked a stress situation in the body using drugs. They then examined the brain activity using functional MRI scanning.

The scientists found that the interaction of the stress hormones hydrocortisone and noradrenaline shut down the activity of brain regions for goal-directed behavior. Yet the brain regions responsible for habitual behavior remained unaffected.

During the research on different stress hormones, the cognitive psychologists used three substances: a placebo, the stress hormone hydrocortisone and yohimbine. Yohimbine is a product which ensures that the stress hormone noradrenaline stays active longer.

Some study participants received hydrocortisone alone or just yohimbine, while other participants received both substances. A fourth group was administered a placebo. Altogether, 69 volunteers participated in the study.

During the experiment, all participants, both male and female, learned that they would receive cocoa or orange juice as a reward if they chose certain symbols on the computer.

After this learning phase, volunteers were allowed to eat as many oranges or as much chocolate pudding as they liked. “This procedure weakens the value of the reward,” said Lars Schwabe, Ph.D.

“Whoever eats chocolate pudding will lose the attraction to cocoa. Whoever is satiated with oranges, has less appetite for orange juice.”

In this context, goal-directed behavior means: Whoever has previously eaten the chocolate pudding chooses the symbols leading to cocoa reward less frequently. Whoever is satiated with oranges selects less frequently the symbols associated with orange juice.

The findings show that only the combination of yohimbine and hydrocortisone attenuates or satisfies goal-directed behavior.

As expected, volunteers who took yohimbine and hydrocortisone did not behave in a goal-directed manner but according to habit. In other words, satiation with oranges or chocolate pudding had no effect.

Persons who had taken a placebo or only one medication, on the other hand, behaved goal-directed and showed a satiating effect.

The brain data revealed: The combination of yohimbine and hydrocortisone reduced the activity in the forebrain – in the so-called orbitofrontal and medial prefrontal cortex.

Researchers say that these areas have been previously associated with goal-directed behavior. The brain regions which are important for habitual learning, on the other hand, were similarly active for all volunteers.

Source: Ruhr-University Bochum

Brain abstract photo by shutterstock.

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