Homer prevents stress-induced cognitive deficits

Before examinations and in critical situations, we need to be particularly receptive and capable of learning. However, acute exam stress and stage fright causes learning blockades and reduced memory function. Scientists from the Max Planck Institute of Psychiatry in Munich have now discovered a mechanism responsible for these cognitive deficits, which functions independently of stress hormones. In animal studies, the researchers show that social stress reduces the volume of Homer-1 in the hippocampus – a region of the brain that plays a central role in learning. This specific protein deficiency leads to altered neuronal activity followed by deterioration in the animals’ learning performance. In the experiments, it was possible to prevent the cognitive deficit by administering additional volumes of the protein to the mice. This suggests that Homer-1 could provide a key molecule for the development of drugs for the treatment of stress-induced cognitive deficits.

Klaus Wagner, a scientist at the Max Planck Institute of Psychiatry, studied the learning behaviour of mice that had been subjected to severe stress. He exposed the animals to social stress – a pressure also frequently experienced by humans today. A male mouse was placed in the cage of an aggressive member of the same species for five minutes. The latter tried to banish the “intruder” by attacking it. Unlike in nature, the test mouse was unable to flee from the cage and was under severe stress, as substantiated by measurements of the stress hormones in its blood.

Following a period of eight hours in which the animal was able to recover in its own cage, its behaviour was examined. While the mouse’s motivation, activity and sensory functions were not impaired at this time, it displayed clear deficits in its learning behaviour. A single five-minute situation of social stress was sufficient, therefore, to impair the animal’s learning performance hours later.

The researchers at the Max Planck Institute then tried to establish which mechanisms were responsible for these cognitive deficits. They identified the protein Homer-1, the concentration of which declines specifically in the hippocampus after exposure to stress. Through its interaction with the neuronal messenger substance glutamate and its receptors, Homer-1 modulates the communication in the neuronal synapses. When the volume of Homer-1 in the hippocampus falls after exposure to stress, the natural receptor activity is severely disrupted and learning capacity declines. The researchers were able to prevent this effect by increasing the Homer-1 concentration again.

Mathias Schmidt, Research Group Leader at the Max Planck Institute of Psychiatry interprets the results as follows: “With our study, we demonstrated the regulation of glutamate-mediated communication in the hippocampus, which directly controls learning behaviour. This mechanism functions independently of stress hormones for the most part. The molecule Homer-1 assumes a key role in this process and will hopefully provide new possibilities in future for targeted pharmaceutical intervention for the avoidance of cognitive deficits.”

Preventing chronic pain with stress management

For chronic pain sufferers, such as people who develop back pain after a car accident, avoiding the harmful effects of stress may be key to managing their condition. This is particularly important for people with a smaller-than-average hippocampus, as these individuals seem to be particularly vulnerable to stress. These are the findings of a study by Dr. Pierre Rainville, PhD in Neuropsychology, Researcher at the Research Centre of the Institut universitaire de gériatrie de Montréal (IUGM) and Professor in the Faculty of Dentistry at Université de Montréal, along with Étienne Vachon-Presseau, a PhD student in Neuropsychology. The study appeared in Brain, a journal published by Oxford University Press.

“Cortisol, a hormone produced by the adrenal glands, is sometimes called the ‘stress hormone’ as it is activated in reaction to stress. Our study shows that a small hippocampal volume is associated with higher cortisol levels, which lead to increased vulnerability to pain and could increase the risk of developing pain chronicity,” explained Étienne Vachon-Presseau.

As Dr. Pierre Rainville described, “Our research sheds more light on the neurobiological mechanisms of this important relationship between stress and pain. Whether the result of an accident, illness or surgery, pain is often associated with high levels of stress Our findings are useful in that they open up avenues for people who suffer from pain to find treatments that may decrease its impact and perhaps even prevent chronicity. To complement their medical treatment, pain sufferers can also work on their stress management and fear of pain by getting help from a psychologist and trying relaxation or meditation techniques.” 

Research summary

This study included 16 patients with chronic back pain and a control group of 18 healthy subjects. The goal was to analyze the relationships between four factors: 1) cortisol levels, which were determined with saliva samples; 2) the assessment of clinical pain reported by patients prior to their brain scan (self-perception of pain); 3) hippocampal volumes measured with anatomical magnetic resonance imaging (MRI); and 4) brain activations assessed with functional MRI (fMRI) following thermal pain stimulations. The results showed that patients with chronic pain generally have higher cortisol levels than healthy individuals. 

Data analysis revealed that patients with a smaller hippocampus have higher cortisol levels and stronger responses to acute pain in a brain region involved in anticipatory anxiety in relation to pain. The response of the brain to the painful procedure during the scan partly reflected the intensity of the patient’s current clinical pain condition. These findings support the chronic pain vulnerability model in which people with a smaller hippocampus develop a stronger stress response, which in turn increases their pain and perhaps their risk of suffering from chronic pain. This study also supports stress management interventions as a treatment option for chronic pain sufferers.

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Stroke Survivors with PTSD More Likely to Avoid Treatment

A new survey of stroke survivors has shown that those with post-traumatic stress disorder (PTSD) are less likely to adhere to treatment regimens that reduce the risk of an additional stroke. Researchers found that 65 percent of stroke survivors with PTSD failed to adhere to treatment, compared with 33 percent of those without PTSD. The survey also suggests that nonadherence in PTSD patients is partly explained by increased ambivalence toward medication. Among stroke survivors with PTSD, approximately one in three (38 percent) had concerns about their medications. Results of the study, led by Columbia University Medical Center researchers, are published today in the British Journal of Health Psychology.

According to data from the American Stroke Association, nearly 795,000 Americans each year suffer a new or recurrent stroke. Stroke is the fourth-leading cause of death and the top cause of disability in the United States. Survivors of strokes are often prescribed treatment regiments, including antiplatelet agents, antihypertensive agents, and statins, which help reduce the risk of subsequent strokes. Previous research has shown that PTSD triggered by medical events—which affects 18 percent of stroke survivors—may impair recovery.

“Unfortunately, too many stroke survivors are not compliant with these regimens, even though we know that adherence to post-stroke treatment regimens is one of the most important components of reducing the risk of a future stroke,” said Ian M. Kronish, MD, MPH, assistant professor of medicine (Center for Behavioral Cardiovascular Health) and one of the study’s authors.

“For those with PTSD, this study shows that concerns about medications are a significant barrier to treatment adherence. Stroke survivors should be assessed for concerns about medications and PTSD symptoms, so that interventions may be introduced as early as possible to get patients back on track to avoid future stroke events.”

Are Crows Mind Readers … Or Just Stressed Out?

Are crows mind readers? Recent studies have suggested that the birds hide food because they think others will steal it — a complex intuition that has been seen in only a select few creatures. Some critics have suggested that the birds might simply be stressed out, but new research reveals that crows may be gifted after all.

Cracks first began forming in the crow mind-reading hypothesis last year. One member of a research team from the University of Groningen in the Netherlands spent 7 months in bird cognition expert Nicola Clayton’s University of Cambridge lab in the United Kingdom studying Western scrub jays, a member of the crow family that is often used for these studies. The Groningen team then developed a computer model in which "virtual jays" cached food under various conditions. In PLOS ONE, they argued that the model showed the jays’ might be moving their food—or recaching it—not because they were reading the minds of their competitors, but simply because of the stress of having another bird present (especially a more dominant one) and of losing food to thieves. The result contradicted previous work by Clayton’s group suggesting that crows might have a humanlike awareness of other creatures’ mental states—a cognitive ability known as theory of mind that has been claimed in dogs, chimps, and even rats.

In the new study, Clayton and her Cambridge graduate student James Thom decided to test the stress hypothesis. First, they replicated earlier work on scrub jays by letting the birds hide peanuts in trays of ground corn cobs—either unobserved or with another bird watching—and later giving them a chance to rebury them. As in previous studies, the jays recached a much higher proportion of the peanuts if another bird could see them: nearly twice as much as in private, the team reports online today in PLOS ONE.

A New Focus on the ‘Post’ in Post-Traumatic Stress

Psychological trauma dims tens of millions of lives around the world and helps create costs of at least $42 billion a year in the United States alone. But what is trauma, exactly?

Both culturally and medically, we have long seen it as arising from a single, identifiable disruption. You witness a shattering event, or fall victim to it — and as the poet Walter de la Mare put it, “the human brain works slowly: first the blow, hours afterward the bruise.” The world returns more or less to normal, but you do not.

In 1980, the Diagnostic and Statistical Manual of Mental Disorders defined trauma as “a recognizable stressor that would evoke significant symptoms of distress in almost everyone” — universally toxic, like a poison.

But it turns out that most trauma victims — even survivors of combat, torture or concentration camps — rebound to live full, normal lives. That has given rise to a more nuanced view of trauma — less a poison than an infectious agent, a challenge that most people overcome but that may defeat those weakened by past traumas, genetics or other factors.

Now, a significant body of work suggests that even this view is too narrow — that the environment just after the event, particularly other people’s responses, may be just as crucial as the event itself.

The idea was demonstrated vividly in two presentations this fall at the Interdisciplinary Conference on Culture, Mind and Brain at the University of California, Los Angeles. Each described reframing a classic model of traumatic experience — one in lab rats, the other in child soldiers.

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Researchers demonstrate that a saliva analysis can reveal decision-making skills

A study conducted by researchers at the University of Granada Group of Neuropsychology and Clinical Psychoneuroimmunology has demonstrated that cortisol levels in saliva are associated with a person’s ability to make good decisions in stressful situations.

To perform this study, the researchers exposed the participants (all women) to a stressful situation by using sophisticated virtual reality technology. The study revealed that people who are not skilled in decision-making have lower baseline cortisol levels in saliva as compared to skilled people.

Cortisol –known as the stress hormone– is a steroid hormone segregated at the adrenal cortex and stimulated by the adrenocorticotropic (ACTH) hormone, which is produced at the pituitary gland. Cortisol is involved in a number of body systems and plays a relevant role in the muscle-skeletal system, blood circulation, the immune system, the metabolism of fats, carbohydrates and proteins and the nervous system.

Recent studies have demonstrated that stress can influence decision making in people. This cognitive component might be considered one of the human resources for coping with stress.

Postpartum women less stressed by threats unrelated to the baby

Following the birth of a child, new mothers may have an altered perception of stresses around them, showing less interest in threats unrelated to the baby. This change to the neuroendocrine circuitry could help the mothers adapt to the additional stress often accompanying newborns, say researchers from Indiana University’s Kinsey Institute and the University of Zurich.

When viewing disturbing images during the study, postpartum women reported less distress and demonstrated less activity in their amygdala, the part of the brain that controls emotional response, than nulliparous, or childless, women, according to functional magnetic resonance imaging.

When the childless women were administered a nasal spray containing the hormone oxytocin, however, their brain images looked more similar to the postpartum women, and they also reported less subjective stress when viewing the images.

"Our findings extend previous work showing a lower stress response with motherhood that likely enhances her ability to cope with this dramatic new role," said lead author Heather Rupp, director of psychology and neuroscience at Brain Surgery Worldwide Inc. and a research fellow at The Kinsey Institute for Research in Sex, Gender and Reproduction.

The study, “Amygdala response to negative images in postpartum verses nulliparous women and intranasal oxytocin,” was published in the online journal Social Cognitive and Affective Neuroscience.

Study supports link between stress, epileptic seizures

Scientists have long thought that stress plays a role in epileptic seizures, and new evidence suggests that epilepsy patients who believe this is the case experience a different brain response when faced with a nerve-wracking situation.

Researchers from the University of Cincinnati performed functional MRI brain scans during a stressful math exercise on 16 epilepsy patients who pegged stress as a factor in their seizure control and seven patients who did not. While both groups performed similarly on the test, those who perceived stress to have an impact on their epilepsy showed greater brain activation than the others during intimidating parts of the test.

"One of the things we often hear is that a lot of epilepsy patients feel their seizures are affected by stress … but no one had really looked at their [brain response] or other elements of their physiological response," said study author Jane Allendorfer, an instructor of neurology at the University of Alabama at Birmingham. Allendorfer worked at University of Cincinnati while the study was conducted.

"We were a bit surprised to see this difference," she added, "but really excited to see it as well because this is something that hadn’t been done before."

The research was scheduled to be presented Monday at the annual meeting of the American Epilepsy Society, in San Diego. Data presented at scientific conferences often has not been peer-reviewed or published and is considered preliminary.

A brain disorder producing repeated seizures, epilepsy affects more than 2 million people in the United States, according to the U.S. Centers for Disease Control and Prevention. An estimated 50 million to 65 million people are affected by the condition worldwide.

Childhood trauma leaves mark on DNA of some victims

Abused children are at high risk of anxiety and mood disorders, as traumatic experience induces lasting changes to their gene regulation. Scientists from the Max Planck Institute of Psychiatry in Munich have now documented for the first time that genetic variants of the FKBP5 gene can influence epigenetic alterations in this gene induced by early trauma. In individuals with a genetic predisposition, trauma causes long-term changes in DNA methylation leading to a lasting dysregulation of the stress hormone system. As a result, those affected find themselves less able to cope with stressful situations throughout their lives, frequently leading to depression, post-traumatic stress disorder or anxiety disorders in adulthood. Doctors and scientists hope these discoveries will yield new treatment strategies tailored to individual patients, as well as increased public awareness of the importance of protecting children from trauma and its consequences.