Whenever we have to acquire new knowledge under stress, the brain deploys unconscious rather than conscious learning processes. Neuroscientists at the Ruhr-Universität Bochum have discovered that this switch from conscious to unconscious learning systems is triggered by the intact function of mineralocorticoid receptors. These receptors are activated by hormones released in response to stress by the adrenal cortex. The team of PD Dr Lars Schwabe from the Institute of Cognitive Neuroscience, together with colleagues from the neurology department at the university clinic Bergmannsheil, reports in the journal “Biological Psychiatry”.
Predicting the weather under stress
The team from Bochum has examined 80 subjects, 50 per cent of whom were given a drug blocking mineralocorticoid receptors in the brain. The remaining participants took a placebo drug. Twenty participants from each group were subjected to a stress-inducing experience. Subsequently, all participants underwent a learning test, the so-called weather prediction task. The subjects were shown playing cards with different symbols and had to learn which combinations of cards meant rain and which meant sunshine. The researchers used MRI to record the respective brain activity.
Learning unconsciously or consciously
There are two different approaches to master the weather prediction test: some subjects tried consciously to formulate a rule that would enable them to predict sunshine and rain. Others learned unconsciously to give the right answer, following their gut feeling, as it were. The team of Lars Schwabe demonstrated in August 2012 that, under stress, the brain prefers unconscious to conscious learning. “This switch to another memory system happens automatically,” says Lars Schwabe. “It makes sense for the organism to react in this manner. Thus, learning efficiency can be maintained even under stress.” However, this works only with fully functional mineralocorticoid receptors. Once the researchers blocked these receptors by applying the drug Spironolactone, the participants switched over to the unconscious strategy less frequently, thus demonstrating a poorer learning efficiency.
Effects also visible in brain activity
These effects also became evident in MRI data. Usually, stress causes the brain activity to shift from the hippocampus – a structure for conscious learning – to the dorsal striatum, which manages unconscious learning. However, this stress-induced switch took place only in the placebo group, not in subjects who had been given the mineralocorticoid receptor blocker. Consequently, the mineralocorticoid receptors play a crucial role in enabling the brain to adapt to stressful situations.
New research out of the University of Maryland School of Public Health shows that exercise may improve cognitive function in those at risk for Alzheimer’s by improving the efficiency of brain activity associated with memory. Memory loss leading to Alzheimer’s disease is one of the greatest fears among older Americans. While some memory loss is normal and to be expected as we age, a diagnosis of mild cognitive impairment, or MCI, signals more substantial memory loss and a greater risk for Alzheimer’s, for which there currently is no cure.
The study, led by Dr. J. Carson Smith, assistant professor in the Department of Kinesiology, provides new hope for those diagnosed with MCI. It is the first to show that an exercise intervention with older adults with mild cognitive impairment (average age 78) improved not only memory recall, but also brain function, as measured by functional neuroimaging (via fMRI). The findings are published in the Journal of Alzheimer’s Disease.
“We found that after 12 weeks of being on a moderate exercise program, study participants improved their neural efficiency – basically they were using fewer neural resources to perform the same memory task,” says Dr. Smith. “No study has shown that a drug can do what we showed is possible with exercise.”
Recommended Daily Activity: Good for the Body, Good for the Brain
Two groups of physically inactive older adults (ranging from 60-88 years old) were put on a 12-week exercise program that focused on regular treadmill walking and was guided by a personal trainer. Both groups – one which included adults with MCI and the other with healthy brain function – improved their cardiovascular fitness by about ten percent at the end of the intervention. More notably, both groups also improved their memory performance and showed enhanced neural efficiency while engaged in memory retrieval tasks.
The good news is that these results were achieved with a dose of exercise consistent with the physical activity recommendations for older adults. These guidelines urge moderate intensity exercise (activity that increases your heart rate and makes you sweat, but isn’t so strenuous that you can’t hold a conversation while doing it) on most days for a weekly total of 150 minutes.
Measuring Exercise’s Impact on Brain Health and Memory
One of the first observable symptoms of Alzheimer’s disease is the inability to remember familiar names. Smith and colleagues had study participants identify famous names and measured their brain activation while engaged in correctly recognizing a name – e.g., Frank Sinatra, or other celebrities well known to adults born in the 1930s and 40s. “The task gives us the ability to see what is going on in the brain when there is a correct memory performance,” Smith explains.
Tests and imaging were performed both before and after the 12-week exercise intervention. Brain scans taken after the exercise intervention showed a significant decrease in the intensity of brain activation in eleven brain regions while participants correctly identified famous names. The brain regions with improved efficiency corresponded to those involved in the pathology of Alzheimer’s disease, including the precuneus region, the temporal lobe, and the parahippocampal gyrus.
The exercise intervention was also effective in improving word recall via a “list learning task,” i.e., when people were read a list of 15 words and asked to remember and repeat as many words as possible on five consecutive attempts, and again after a distraction of being given another list of words.
“People with MCI are on a very sharp decline in their memory function, so being able to improve their recall is a very big step in the right direction,” Smith states.
The results of Smith’s study suggest that exercise may reduce the need for over-activation of the brain to correctly remember something. That is encouraging news for those who are looking for something they can do to help preserve brain function.
Dr. Smith has plans for a larger study that would include more participants, including those who are healthy but have a genetic risk for Alzheimer’s, and follow them for a longer time period with exercise in comparison to other types of treatments. He and his team hope to learn more about the impact of exercise on brain function and whether it could delay the onset or progression of Alzheimer’s disease.
Many people complain about poor sleep around the full moon, and now a report appearing in Current Biology, a Cell Press publication, on July 25 offers some of the first convincing scientific evidence to suggest that this really is true. The findings add to evidence that humans—despite the comforts of our civilized world—still respond to the geophysical rhythms of the moon, driven by a circalunar clock.
"The lunar cycle seems to influence human sleep, even when one does not ‘see’ the moon and is not aware of the actual moon phase," says Christian Cajochen of the Psychiatric Hospital of the University of Basel.
In the new study, the researchers studied 33 volunteers in two age groups in the lab while they slept. Their brain patterns were monitored while sleeping, along with eye movements and hormone secretions.
The data show that around the full moon, brain activity related to deep sleep dropped by 30 percent. People also took five minutes longer to fall asleep, and they slept for twenty minutes less time overall. Study participants felt as though their sleep was poorer when the moon was full, and they showed diminished levels of melatonin, a hormone known to regulate sleep and wake cycles.
"This is the first reliable evidence that a lunar rhythm can modulate sleep structure in humans when measured under the highly controlled conditions of a circadian laboratory study protocol without time cues," the researchers say.
Cajochen adds that this circalunar rhythm might be a relic from a past in which the moon could have synchronized human behaviors for reproductive or other purposes, much as it does in other animals. Today, the moon’s hold over us is usually masked by the influence of electrical lighting and other aspects of modern life.
The researchers say it would be interesting to look more deeply into the anatomical location of the circalunar clock and its molecular and neuronal underpinnings. And, they say, it could turn out that the moon has power over other aspects of our behavior as well, such as our cognitive performance and our moods.
Something odd happened when Shu Zhang was giving a presentation to her classmates at the Columbia Business School in New York City. Zhang, a Chinese native, spoke fluent English, yet in the middle of her talk, she glanced over at her Chinese professor and suddenly blurted out a word in Mandarin. “I meant to say a transition word like ‘however,’ but used the Chinese version instead,” she says. “It really shocked me.”
Shortly afterward, Zhang teamed up with Columbia social psychologist Michael Morris and colleagues to figure out what had happened. In a new study, they show that reminders of one’s homeland can hinder the ability to speak a new language. The findings could help explain why cultural immersion is the most effective way to learn a foreign tongue and why immigrants who settle within an ethnic enclave acculturate more slowly than those who surround themselves with friends from their new country.
Previous studies have shown that cultural icons such as landmarks and celebrities act like “magnets of meaning,” instantly activating a web of cultural associations in the mind and influencing our judgments and behavior, Morris says. In an earlier study, for example, he asked Chinese Americans to explain what was happening in a photograph of several fish, in which one fish swam slightly ahead of the others. Subjects first shown Chinese symbols, such as the Great Wall or a dragon, interpreted the fish as being chased. But individuals primed with American images of Marilyn Monroe or Superman, in contrast, tended to interpret the outlying fish as leading the others. This internally driven motivation is more typical of individualistic American values, some social psychologists say, whereas the more externally driven explanation of being pursued is more typical of Chinese culture.
To determine whether these cultural icons can also interfere with speaking a second language, Zhang, Morris, and their colleagues recruited male and female Chinese students who had lived in the United States for a less than a year and had them sit opposite a computer monitor that displayed the face of either a Chinese or Caucasian male called “Michael Lee.” As microphones recorded their speech, the volunteers conversed with Lee, who spoke to them in English with an American accent about campus life.
Next, the team compared the fluency of the volunteers’ speech when they were talking to a Chinese versus a Caucasian face. Although participants reported a more positive experience chatting with the Chinese version of “Michael Lee,” they were significantly less fluent, producing 11% fewer words per minute on average, the authors report online today in the Proceedings of the National Academy of Sciences. “It’s ironic” that the more comfortable volunteers were with their conversational partner, the less fluent they became, Zhang says. “That’s something we did not expect.”
To rule out the possibility that the volunteers were speaking more fluently to the Caucasian face on purpose, thus explaining the performance gap, Zhang and colleagues asked the participants to invent a story, such as a boy swimming in the ocean, while simultaneously being exposed to Chinese and American icons rather than faces. Seeing Chinese icons such as the Great Wall also interfered with the volunteers’ English fluency, causing a 16% drop in words produced per minute. The icons also made the volunteers 85% more likely to use a literal translation of the Chinese word for an object rather than the English term, Zhang says. Rather than saying “pistachio,” for example, volunteers used the Chinese version, “happy nuts.”
Understanding how these subtle cultural cues affect language fluency could help employers design better job interviews, Morris says. For example, taking a Japanese job candidate out for sushi, although a well-meaning gesture, might not be the best way to help them shine.
“It’s quite striking that these effects were so robust,” says Mary Helen Immordino-Yang, a developmental psychologist at the University of Southern California in Los Angeles. They show that “we’re exquisitely attuned to cultural context,” she says, and that “even subtle cues like the ethnicity of the person we’re talking to” can affect language processing. The take-home message? “If one wants to acculturate rapidly, don’t move to an ethnic enclave neighborhood where you’ll be surrounded by people like yourself,” Morris says. Sometimes, a familiar face is the last thing you need to see.
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