Stress disrupts human thinking, but the brain can bounce back

The Rockefeller University - Newswire

Stress disrupts human thinking, but the brain can bounce back

A new neuroimaging study on stressed-out students suggests that male humans, like male rats, don’t do their most agile thinking under stress. The findings, published this month in the Proceedings of the National Academy of Sciences, show that 20 male M.D. candidates in the middle of preparing for their board exams had a harder time shifting their attention from one task to another than other healthy young men who were not under the gun.

Previous experiments had found that stressed rats foraging for food had similar impairments and that those problems resulted from stress-induced changes in their brain anatomy. The new study, using functional magnetic resonance imaging (fMRI) to scan the stressed students’ brains, is a robust example of how basic research in an animal model can lead to high-tech investigations of the human brain.

“It’s a great translational story,” says Bruce S. McEwen, head of the Harold and Margaret Milliken Hatch Laboratory of Neuroendocrinology at The Rockefeller University, who worked on the project with colleagues at Weill Cornell Medical College. “The research in the rats led to the imaging work on people, and the results matched up remarkably well.”

The work holds good news too, for both rats and humans: Their brains recuperate quickly. Less than a month after the stress goes away, they are back to normal. “The message is that healthy brains are remarkably resilient and plastic,” McEwen says.

To probe the effects of stress, the researchers scanned the brains of volunteers, some stressed and others relatively relaxed, performing two subtly different kinds of mental tasks, either an attention-shift or a response-reversal. Lying inside the scanner, the subjects looked at two discs: one red and one green, with one moving up and the other down. In a series of trials, they were prompted to choose a disc according to motion or color. By ordering when the subjects did which tasks, they challenged their volunteers’ brains to either switch focus from color to motion, or to suddenly reverse their choice of a disc in the same category.

“It’s like the old story about the American crossing the road in England,” says Conor Liston, an M.D.-Ph.D. student at Rockefeller and Cornell, who led the research. A response-reversal requires the brain to override the habitual impulse to first look left instead of right for oncoming cars. An American in Venice might require an attention-shift, by contrast, to seek out boats instead of evading cars.

In earlier research on rats, neuroscientists found that these two tasks place demands on different circuits in the brain, and the circuits are affected in different ways by stress. In particular, collaborative work by McEwen and John Morrison at Mount Sinai Medical Center have shown that repeated stress on rats shriveled nerve cells of the medial prefrontal cortex, and that a shrunken prefrontal cortex is linked to slower performance on attention-shifting tasks. In those experiments, rats learned to dig through a certain texture, like sawdust, in the presence of an irrelevant odor to find food; then the researchers made odor, rather than texture, the clue for finding the food and measured how long it took the rats to switch their foraging strategies. But while the restricted prefrontal cortex — a larger version of which is thought to play a role in the “executive function” in humans — slowed the rats’ performance on attention-shifts, it did not change their performance on response-reversal tasks. In fact, neurons in a different part of the brain thought to be involved in response-reversals, the orbital frontal cortex, actually grew larger from the stress.

The new research suggests that something very similar may happen to distressed humans. Liston, working with B.J. Casey at the Sackler Institute at Weill Cornell, used fMRI to explore his hunch that the brains of rats and men have some basic processes in common — that stress would also impair performance on attention-shifting tasks and diminish activity in the medial prefrontal cortex.

He found that male med students who said they were stressed out one month before they were to take their boards fared much worse on attention-shifting tasks than similar healthy adults who claimed to be taking it easy. The high stress levels, gauged by an established measure called the perceived stress scale, were also tightly associated with diminished activity in the prefrontal cortex. But their performance on response-reversals was unimpaired. Finally, as was found in the rats, when Liston scanned the students again one month after the test, he discovered that their attention-shifting performance had returned to normal along with their brains.

The uncanny similarities surprised even the researchers. “I certainly don’t want to say that rat brains are just like human brains,” Liston says. “But it does show that you can use research in animal models to help interpret human neuroimaging results.”

Liston plans to next explore how stress impacts the rest of the brain. He also wants to investigate whether or not there are differences in how the brains of men and women respond to stress. “Stress is doing a whole lot of things in your brain that we don’t understand yet, but we know that it is intimately involved in a wide range of neuropsychiatric disorders,” Liston says. A mechanistic understanding of stress could lead to insights into associated psychiatric problems, he says.

Proceedings of the National Academy of Sciences online: January 12, 2009

Mellow Demeanor May Stave Off Dementia | LiveScience

Mellow Demeanor May Stave Off Dementia | LiveScience

Results showed that among people who were socially isolated, those who were calm and relaxed were 50 percent less likely to develop dementia compared with individuals who were prone to distress. Also, among the outgoing extroverts, the dementia risk was also 50 percent lower for people who were calm compared with those who were prone to distress.

The researchers say the ability to handle stress without anxiety could help to explain the findings.

Neuroscientists Find That Men And Women Respond Differently To Stress

Men Are From Mars -- Neuroscientists Find That Men And Women Respond Differently To Stress

Neuroscientists Find That Men And Women Respond Differently To Stress

Functional magnetic resonance imaging of men and women under stress
showed neuroscientists how their brains differed in response to
stressful situations. In men, increased blood flow to the left
orbitofrontal cortex suggested activation of the "fight or flight"
response. In women, stress activated the limbic system, which is
associated with emotional responses.

Facial expressions and the regulation of emotions.

Facial expressions and the regulation of emotions. [J Pers Soc Psychol. 1990] - PubMed Result

In the two decades since contemporary psychologists produced strong evidence confirming Darwin's century-old hypothesis of the innateness and universality of certain facial expressions of emotions, research on expressive behavior has become well established in developmental, social, and personality psychology and in psychophysiology. There are also signs of increased interest in emotions in clinical psychology and the neurosciences. Despite the success of the work on emotion expression and the upward trend of interest in emotions in general, the fundamental issue of the relation between emotion expression and emotion experience or feeling state remains controversial. A new developmental model of expression-feeling relations provides a framework for reevaluating previous research and for understanding the conditions under which expressions are effective in activating and regulating feeling states. The model has implications for research, socialization practices, and psychotherapy.

Facial expressions of emotion: an old controversy and new findings.

Facial expressions of emotion: an old controversy ...[Philos Trans R Soc Lond B Biol Sci. 1992] - PubMed Result

Evidence on universals in facial expression of emotion and renewed controversy about how to interpret that evidence is discussed. New findings on the capability of voluntary facial action to generate changes in both autonomic and central nervous system activity are presented, as well as a discussion of the possible mechanisms relevant to this phenomenon. Finally, new work on the nature of smiling is reviewed which shows that it is possible to distinguish the smile when enjoyment is occurring from other types of smiling. Implications for the differences between voluntary and involuntary expression are considered.

Voluntary facial action generates emotion-specific autonomic nervous system activity

Voluntary facial action generates emotion-specific...[Psychophysiology. 1990] - PubMed Result

Four experiments were conducted to determine whether voluntarily produced emotional facial configurations are associated with differentiated patterns of autonomic activity, and if so, how this might be mediated. Subjects received muscle-by-muscle instructions and coaching to produce facial configurations for anger, disgust, fear, happiness, sadness, and surprise while heart rate, skin conductance, finger temperature, and somatic activity were monitored. Results indicated that voluntary facial activity produced significant levels of subjective experience of the associated emotion, and that autonomic distinctions among emotions: (a) were found both between negative and positive emotions and among negative emotions, (b) were consistent between group and individual subjects' data, (c) were found in both male and female subjects, (d) were found in both specialized (actors, scientists) and nonspecialized populations, (e) were stronger when the voluntary facial configurations most closely resembled actual emotional expressions, and (f) were stronger when experience of the associated emotion was reported. The capacity of voluntary facial activity to generate emotion-specific autonomic activity: (a) did not require subjects to see facial expressions (either in a mirror or on an experimenter's face), and (b) could not be explained by differences in the difficulty of making the expressions or by differences in concomitant somatic activity.

micro expression muscles

Autonomic nervous system activity distinguishes am...[Science. 1983] - PubMed Result

Emotion-specific activity in the autonomic nervous system was generated by constructing facial prototypes of emotion muscle by muscle and by reliving past emotional experiences. The autonomic activity produced distinguished not only between positive and negative emotions, but also among negative emotions. This finding challenges emotion theories that have proposed autonomic activity to be undifferentiated or that have failed to address the implications of autonomic differentiation in emotion.

Smile your mood

How to Lift Your Mood? Try Smiling - TIME

I was skeptical until I read a paper in the January issue of the Journal of Personality and Social Psychology, a peer-reviewed publication of the American Psychological Association. That paper led me to other papers, and it turns out the trainer is right: The face isn't a pressure-relief valve. It is more like a thermostat. When you turn down the setting, the machinery inside has to do less work.

In the Journal of Personality and Social Psychology paper, David Matsumoto of San Francisco State University and Bob Willingham of the Center for Psychological Studies in Berkeley, Calif., present the results of the first study ever conducted comparing the facial expressions of blind people with those of sighted people in a natural, nonlaboratory setting. Those studied were all judo athletes — blind ones who competed in the 2004 Paralympic Games in Athens and sighted ones who competed in the 2004 Olympics in the same competition hall a few weeks earlier. (See pictures of "Second Place: Faces of Defeat.")

Matsumoto conceived the paper to investigate one of the oldest dilemmas in the study of physiology. We have known for many years that people all over the world, even those from remote cultures, use the same facial expressions to convey basic emotions like grief or joy. Charles Darwin noted this phenomenon in the 19th century, and Matsumoto's mentor, a famous psychologist named Paul Ekman who traveled the globe in the 1960s, proved that both isolated tribesmen and urban Westerners identified pictures of facial expressions in the same way. Ekman demonstrated that a frown means unhappiness the world over; wide eyes mean fright or surprise; a wrinkled nose means disgust. But no one has yet found the source of these universal expressions: Do we all learn the expressions through our culture, or are facial configurations genetically coded for everyone?

This question has occupied many scientists. Darwin wrote a long, highly entertaining 1872 book, The Expression of the Emotions in Man and Animals, that came to the conclusion — unsurprising, given the author — that the universality of facial expressions owed to their evolutionary origin.

In his concluding chapter, Darwin noted that a pastor who ran a school for the blind told him that "those born blind" and "those gifted with eyesight" display facial expressions equally well. But somehow it took more than 130 years for someone to test this hypothesis scientifically. Matsumoto has finally proved the hypothesis. He examined 123 photographs taken by Willingham, a professional photographer, and carefully coded all the expressions on the athletes' faces. The authors found that regardless of whether the athletes could see, the gold-medal winners were significantly more likely to display real, joyful smiles — those that engage not just the muscles around the mouth but also those around the eyes — than those athletes who got silver medals. The ones who received silvers, whether blind or sighted, were significantly more likely to display social or lying smiles — those in which only the mouth muscles are engaged. (You can tell the difference between real and social smiles after training in facial movements; once you have the training, it's impossible not to study the eyes whenever someone smiles at you.)

Because blind people can't learn cultural cues from looking at others, Matsumoto and Willingham conclude that all of us are born with the ability to express both real and social emotions through our facial expressions. The fact that blind people display fake smiles shows that the skill is probably one we acquired through evolution in order to get along with others. (See pictures of facial yoga.)

Beyond that, what the genetic origin of facial expressions suggests is that the way your face looks is strongly related to what you are feeling inside. What I began to wonder was whether the train might run in the opposite direction: Could you change what you're feeling inside by pulling your face into a different expression? This is what the trainer had suggested: my exercises would be easier if I kept my face passive rather than twisted.

The possibility that your expression could affect your mood was first suggested to me by Marsha Linehan, a University of Washington psychologist who treats suicidal patients. She has found that helping patients modulate their facial expressions — relaxing the face when angry, for instance — can help them control their emotions. Ekman and his colleagues provided evidence of this in a Science paper back in 1983. They found that those instructed to produce certain facial movements showed the same physiological responses as those asked to recall a highly emotional experience. Later, a study showed that if you hold a pencil between your teeth — causing your mouth to approximate a smile — it will be easier for you to find cartoons funny.

In short, the emotional train does run in two directions: between your brain, which may be screaming from the pain that your trainer is causing, and your face, which can — if you draw it into a relaxed expression — inform your brain that it shouldn't be protesting so much. So next time you're working out and grimacing, push your facial muscles into submission. Look blank. You will find it's easier to get through one more rep.