Stress Changes Learning in the Brain

A 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.

Brain Scans Show Teen Drinking Impairs Brain Efficiency

New research suggests brains scans can identify patterns of brain activity that may predict if a teen will develop into a problem drinker.

The study also confirms that heavy drinking affects a teenagers’ developing brain.

Using special MRI scans, researchers looked at forty 12- to 16-year-olds who had not started drinking yet, then followed them for about three years and scanned them again.

Researchers discovered that half of the teens started to drink alcohol fairly heavily during this interval.

Investigators also found that kids who had initially showed less activation in certain brain areas were at greater risk for becoming heavy drinkers in the next three years.

However, once the teens started drinking, their brain activity looked like the heavy drinkers’ in the other studies — that is, their brains showed more activity as they tried to perform memory tests.

“That’s the opposite of what you’d expect, because their brains should be getting more efficient as they get older,” said lead researcher Lindsay M. Squeglia, Ph.D., of the University of California, San Diego.

Researchers say an operational definition of heavy drinking typically included episodes of having four or more drinks on an occasion for females and five or more drinks for males.

The findings add to evidence that heavy drinking has consequences for teenagers’ developing brains. But they also add a new layer: There may be brain activity patterns that predict which kids are at increased risk for heavy drinking.

“It’s interesting because it suggests there might be some pre-existing vulnerability,” Squeglia said.

Researchers say they are not advocating for teens to receive MRIs to determine their risk of excessive alcohol consumption. But the findings do give clues into the biological origins of kids’ problem drinking.

Experts say the findings suggest that heavy drinking may affect young people’s brains right at the time when they need to be working efficiently.

“You’re learning to drive, you’re getting ready for college. This is a really important time of your life for cognitive development,” Squeglia said.

She noted that all of the study participants were healthy, well-functioning kids. It’s possible that teens with certain disorders — like depression or ADHD — might show greater effects from heavy drinking.

Source: Journal of Studies on Alcohol and Drugs

Stress Hormones Impede Healthy Behavioral Change

For 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.