How repeated stress impairs memory
Anyone who has ever been subject to chronic stress knows that it can take a toll on emotions and the ability to think clearly. Now, new research uncovers a neural mechanism that directly links repeated stress with impaired memory. The study, published by Cell Press in the March 8 issue of the journal Neuron, also provides critical insight into why stress responses can act as a trigger for many mental illnesses.
Stress hormones are known to influence the prefrontal cortex (PFC), a brain region that controls high level “executive” functions such as working memory and decision making. “Previous work has shown that chronic stress impairs PFC-mediated behaviors, like mental flexibility and attention. However, little is known about the physiological consequences and molecular targets of long-term stress in PFC, especially during the adolescent period when the brain is more sensitive to stressors,” explains the author this study, Dr. Zhen Yan, from the State University of New York at Buffalo. “
Dr. Yan and colleagues examined whether repeated stress had a negative influence on glutamate receptors in juvenile rats. Glutamate signaling plays a critical role in PFC function. They found that in response to repeated stress, there was a significant loss of glutamate receptors, which resulted in a deficit of PFC-mediated cognitive processes. The researchers went on to identify the molecular mechanisms that linked stress with the decrease in glutamate receptors and demonstrated that if they blocked these mechanisms, the stress-induced decrease in both glutamate receptors and recognition memory could be prevented.
Taken together, the findings identify a loss of glutamate receptors as an important target of repeated stress and link chronic stress with abnormal PFC function. “Since PFC dysfunction has been implicated in various stress-related mental disorders, delineating molecular mechanisms by which stress affects the PFC should be critical for understanding the role of stress in influencing the disease process,” concludes Dr. Yan.
High Stress Hormone Levels Impair Memory
St. Louis, June 15, 1999 - If it’s been a really, really tough week at work and you can’t remember where you put your car keys, it may be that high levels of the stress hormone cortisol are interfering with your memory. In the June Archives of General Psychiatry, investigators at Washington University School of Medicine in St. Louis provide the first direct evidence that several days of exposure to cortisol at levels associated with major physical or psychological stresses can have a signifcant negative effect on memory.
“We tested memory and other cognitive functions before treatment, after one day of treatment and again after four days, in individuals receiving either a high dose of cortisol, a lower dose or an inactive substance,” explained lead author John W. Newcomer, M.D., assistant professor of psychiatry and psychology. “We saw memory impairment only in the individuals treated with the higher dose and only after four days of exposure. The good news is it appears that it would take several days of stresses like major surgery or severe psychological trauma in order for cortisol to produce memory impairment. And after a one-week wash-out period, memory performance returned to the untreated levels.”
Cortisol is produced in the body during stress. It belongs to a family of stress hormones called glucocorticoids that, among other actions, can interfere with energy supply to certain brain cells involved in memory. Newcomer’s previous work showed that treatments with a synthetic glucocorticoid called dexamethasone impaired memory. But this is the first study to demonstrate that prolonged exposure to high levels of cortisol-the hormone actually produced in the body in response to high stress- has that same negative effect.
Studies have illustrated the strong link between insomnia and chronic stress and, according to APA’s 2010 Stress in America survey, more than 40 percent of all adults say they lie awake at night because of stress. Experts recommend going to bed at a regular time each night, striving for at least seven to eight hours of sleep and eliminating distractions such as television and computers from the bedroom.
Stress Insomnia
Stress has mental, emotional and physical components. Insomnia is mostly a result of mental tension.
As stress becomes prolonged, the ability to focus becomes a limitation instead. The mind is unable to let go. The conscious mind doesn’t see a clear solution for a problematic situation, and basically dumps it on the subconscious, which tries to solve it through brute force.
Constant stress lowers the level of consciousness and affixes it there. If we can raise the level of consciousness, we can look from other perspectives, solve the problem and hopefully release the stress. Insomnia occurs when we don’t let it go lower either, in which case we disrupt a natural cycle, rob the body of natural rest and try to force inadequate solutions on the subconscious.
To heal stress related insomnia, there is only one choice: to completely let go of the stressful situation and accept the consequences. By doing so we allow the subconscious to do its recuperative magic, and provide the conscious mind with much needed deep rest.