Stress thwarts our ability to plan ahead by disrupting how we use memory

April 3, 2020

Science Daily/Stanford University

New research from Stanford University has found that stress can hinder our ability to develop informed plans by preventing us from being able to make decisions based on memory.

"We draw on memory not just to project ourselves backward into the past but to project ourselves forward, to plan," said Stanford psychologist Anthony Wagner, who is the senior author of the paper detailing this work, published April 2 in Current Biology. "Stress can rob you of the ability to draw on cognitive systems underlying memory and goal-directed behavior that enable you to solve problems more quickly, more efficiently and more effectively."

Combined with previous work from Wagner's Memory Lab and others, these findings could have broad implications for understanding how different people plan for the future -- and how lack of stress may afford some people a greater neurologically-based opportunity to think ahead.

"It's a form of neurocognitive privilege that people who are not stressed can draw on their memory systems to behave more optimally," said Wagner, who is the Lucie Stern Professor in the Social Sciences at Stanford's School of Humanities and Sciences. "And we may fail to actually appreciate that some individuals might not be behaving as effectively or efficiently because they are dealing with something, like a health or economic stressor, that reduces that privilege."

Take a virtual walk

The researchers conducted experiments where they monitored participants' behavior and brain activity -- via fMRI -- as they navigated through virtual towns. After participants became very familiar winding routes in a dozen towns, they were dropped onto one of the memorized paths and told to navigate to a goal location.

To test the effects of stress, the researchers warned some participants that they could receive a mild electric shock, unrelated to their performance, during their virtual rambles. Participants who didn't have to worry about being randomly shocked tended to envision and take novel shortcuts based on memories acquired from prior journeys, whereas the stressed participants tended to fall back on the meandering, habitual routes.

Prior to beginning their trek, the participants were virtually held in place at their starting position. Brain scans from this period showed that the stressed individuals were less likely than their counterparts to activate the hippocampus -- a brain structure that would have been active if they were mentally reviewing previous journeys. They also had less activity in their frontal-parietal lobe networks, which allows us to bring neural processes in line with our current goals. Previous work by the researchers had found that stress hinders this neural machinery, making it harder for us to retrieve and use memories.

The researchers believe their new study is the first to show how hippocampal-frontal lobe network disruption takes memory replay offline during a planning session due to stress.

"Its kind of like our brain is pushed into a more low-level thought-process state, and that corresponds with this reduced planning behavior," said Thackery Brown, who was a postdoctoral scholar in the Memory Lab during this research and is lead author of the paper.

Stress and old age

Looking forward, the researchers are especially interested in how the relationship between stress and memory affects older populations, who often experience both health and economic issues. Older people are also more likely to be concerned about memory loss. Together, these combined stressors could contribute to a diminished ability to remember, which could further exacerbate their stress and also impair their ability to deal with it.

Brown has begun conducting studies similar to the virtual navigation experiments with participants between the ages of 65 and 80 to try to better understand how the associations between stress, memory and planning play out in older populations.

"It's a powerful thing to think about how stressful events might affect planning in your grandparents," said Brown, who is now an assistant professor at Georgia Institute of Technology. "It affects us in our youth and as we interact with and care for older members of our family, and then it becomes relevant to us in a different way when we are, ourselves, older adults."

https://www.sciencedaily.com/releases/2020/04/200403115103.htm

Stress can impair memory, reduce brain size in middle age

October 25, 2018

Science Daily/University of Texas Health Science Center at San Antonio

Stress may be causing impaired memory and brain shrinkage in middle-age adults, even before symptoms of Alzheimer's or other dementia begin, according to a new study.

Adults in their 40s and 50s with higher levels of cortisol -- a hormone linked to stress -- performed worse on memory and other cognitive tasks than peers of the same age with average cortisol levels, research found. Higher cortisol in the blood also was associated with smaller brain volumes, according to the study, published Oct. 24 in Neurology, the medical journal of the American Academy of Neurology.

"In our quest to understand cognitive aging, one of the factors attracting significant interest and concern is the increasing stress of modern life," said study senior author Sudha Seshadri, M.D., professor of neurology at UT Health San Antonio and founding director of the university's Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases. "One of the things we know in animals is that stress can lead to cognitive decline. In this study, higher morning cortisol levels in a large sample of people were associated with worse brain structure and cognition."

The cognitive data are from 2,231 participants in the Framingham Heart Study, for which Dr. Seshadri is a senior investigator; 2,018 participants also underwent magnetic resonance imaging (MRI) to measure brain volume. The team included Framingham collaborators at Harvard Medical School; the National Heart, Lung, and Blood Institute; Boston University School of Medicine; the University of California, Davis, at Sacramento; and UT Health San Antonio.

Blood serum cortisol, which varies in level throughout the day, was measured in early morning (between 7:30 and 9 a.m.) in each fasting participant. The study featured a relatively young sample of male and female participants (mean age 48.5).

"Cortisol affects many different functions, so it is important to fully investigate how high levels of the hormone may affect the brain," said study lead author Justin B. Echouffo-Tcheugui, M.D., Ph.D., of Harvard Medical School. "While other studies have examined cortisol and memory, we believe our large, community-based study is the first to explore, in middle-aged people, fasting blood cortisol levels and brain volume, as well as memory and thinking skills."

Memory loss and brain shrinkage were found in the study's middle-age participants before the onset of any symptoms, Dr. Echouffo-Tcheugui noted. He said it is important for physicians to counsel people with higher cortisol levels on ways to reduce stress, such as getting enough sleep and engaging in moderate exercise.

"The faster pace of life today probably means more stress, and when we are stressed, cortisol levels increase because that is our fight-or-flight response," Dr. Seshadri said. "When we are afraid, when we are threatened in any way, our cortisol levels go up. This study adds to the prevailing wisdom that it's never too early to be mindful of reducing stress."

Findings were adjusted for factors including age, sex, smoking and body mass index. The team asked whether having APOE4, a genetic risk factor for cardiovascular disease and Alzheimer's disease, might be associated with higher cortisol level. This did not prove to be the case.

https://www.sciencedaily.com/releases/2018/10/181025084043.htm

Severe stress behind self-perceived memory problems

August 31, 2017

Science Daily/University of Gothenburg

Stress, fatigue, and feeling like your memory is failing you. These are the symptoms of a growing group of patients. Result – They may need help, but they are rarely entering the initial stages of dementia.

"We are seeing a growing number of people who are seeking help because of self-perceived cognitive problems, but have no objective signs of disease despite thorough investigation," says Marie Eckerström, doctoral student at the Institute of Neuroscience and Physiology and licensed psychologist at the Memory Unit of Sahlgrenska University Hospital.

The influx of this particular group of patients, which currently represents one-third of the individuals who come to the unit, has increased the need for knowledge of who they are. In her work, Marie Eckerström followed a few hundred of them, both women and men, over an average of four years.

They are usually highly educated professionals who are relatively young in this context, between the ages of 50 and 60. When tested at the hospital, their memory functions are intact. But, in their everyday environment where they are under pressure to constantly learn new things, they think things just are not working right.

The correlation between self-perceived memory problems and stress proved to be strong. Seven out of ten in the group had experiences of severe stress, clinical burnout, or depression.

"We found that problems with stress were very common. Patients often tell us they are living or have lived with severe stress for a prolonged period of time and this has affected their cognitive functions to such an extent that they feel like they are sick and are worried about it. In some cases, this is combined with a close family member with dementia, giving the patient more knowledge but also increasing their concern," says Marie Eckerström.

The memory unit investigates suspicions of the early stages of dementia in those who seek help. Research is conducted in parallel to this.

"We primarily investigate suspected dementia. If we are able to rule this out, then the patient does not remain with us. But, there are not so many places such patients can turn and they seem to fall between the cracks."

Perceived memory problems are common and may be an early sign of future development of dementia. For those in the studied group who also had deviating biomarkers in their cerebrospinal fluid (beta-amyloid, total-tau and phospho-tau), the risk of deteriorating and developing dementia was more than double. However, the majority demonstrated no signs of deterioration after four years.

"These individuals have no objective signs of dementia. The issue instead is usually stress, anxiety or depression," says Marie Eckerström.

One out of ten with only self-perceived memory problems developed dementia during the investigated period. According to Marie Eckerström, this is a higher percentage than the population in general, but is still low.

"It is not a matter of just anyone who has occasional memory problems in everyday life. It is more a matter of individuals who sought medical attention to investigate whether they are developing serious problems," states Marie Eckerström.

https://www.sciencedaily.com/releases/2017/08/170831093346.htm