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
How the olfactory brain affects memory
April 29, 2019
Science Daily/Ruhr-University Bochum
How sensory perception in the brain affects learning and memory processes is far from fully understood. Two neuroscientists of Ruhr-Universität Bochum (RUB) have discovered a new aspect of how the processing of odours impacts memory centres. They showed that the piriform cortex -- a part of the olfactory brain -- has a direct influence on information storage in our most important memory structure, the hippocampus. Dr. Christina Strauch and Professor Denise Manahan-Vaughan report about their findings in the online edition of the magazine Cerebral Cortex on 9 April 2019.
Electric impulses simulate odours
To find out how odours affect memory formation, the researchers triggered an artificial perception of an odour in the brains of rats. To do this, they stimulated the piriform cortex with electrical impulses. "We were very surprised to see that the hippocampus directly responds to stimulation of the piriform cortex," remarked Christina Strauch.
The hippocampus uses sensory information to create complex memories. The basis of this processes is its ability to increase the efficacy of information transmission across synapses and thereby store memory contents. This process is called synaptic plasticity. Manahan-Vaughan and Strauch were the first to show that stimulation of the anterior piriform cortex triggers synaptic plasticity in the hippocampus.
Special role for olfaction
In a second step, the researchers examined to what extent the piriform cortex competes with the entorhinal cortex in driving hippocampal synaptic plasticity. This structure sends information about activity in all sensory modalities to the hippocampus. Activating the afferent pathway of this structure, called the perforant path, triggered completely different reaction patterns in the hippocampus, to those generated by the piriform cortex. "The study gives us a theoretical basis for understanding how olfaction plays such a special role in memory formation and retrieval," commented Denise Manahan-Vaughan.
https://www.sciencedaily.com/releases/2019/04/190429125422.htm