Memories linked with strong emotions often become seared in the brain.
Most people can remember where they were on 9/11, or what the weather was like on the day their first child was born. Memories about world events on Sept 10, or lunch last Tuesday, have long been erased.
Why are memories attached to emotions so strong?
“It makes sense we don’t remember everything,” says René Hen, PhD, professor of psychiatry and neuroscience at Columbia University Vagelos College of Physicians and Surgeons. “We have limited brain power. We only need to remember what’s important for our future wellbeing.”
Fear, in this context, is not just a momentary feeling but a learning experience critical to our survival. When a new situation makes us fearful, the brain records the details in our neurons to help us avoid similar situations in the future, or use appropriate caution.
What’s still a mystery is why these memories, recorded by the brain’s hippocampus, become so strong.
To find out, Hen and Jessica Jimenez, an MD/PhD student at Columbia, placed mice into new, frightening environments and recorded the activity of hippocampal neurons that reach out to the brain’s fear center (the amygdala). The neurons’ activity was also recorded a day later when the mice tried to retrieve memories of the experience.
Unsurprisingly, neurons that respond to the frightening environment send that information to the brain’s fear center.
Here’s what’s surprising about the study
“What was surprising was that these neurons were synchronized when the mouse later recalled the memory,” Hen says.
“We saw that it’s the synchrony that is critical to establish the fear memory, and the greater the synchrony, the stronger the memory,” Jimenez adds. “These are the types of mechanisms that explain why you remember salient events.”
How and when synchronization occurs
How and when synchronization occurs is still unknown, but the answer could reveal the inner workings of the brain that create lifelong memories and lead to new treatments for posttraumatic stress disorder.
“In people with PTSD, many similar events remind them of the original frightening situation,” Hen says, “and it’s possible that synchronization of their neurons has become too strong.”
“We’re really trying to dig into the mechanisms of how emotional memories form to find better treatments for people with PTSD and memory disorders in general.”
1. Jessica C. Jimenez, Jack E. Berry, Sean C. Lim, Samantha K. Ong, Mazen A. Kheirbek, Rene Hen. Contextual fear memory retrieval by correlated ensembles of ventral CA1 neurons. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-17270-w
Razi Berry is the founder and publisher of the journal Naturopathic Doctor News & Review, which has been in print since 2005, and the premier consumer-faced website of naturopathic medicine, NaturalPath. She is the host of The Love is Medicine Project docuseries, The Natural Cancer Prevention Summit, The Heart Revolution-Heal, Empower and Follow Your Heart, and the popular 10-week Sugar Free Summer program. From a near death experience as a young girl that healed her failing heart, to later overcoming infertility and chronic fatigue syndrome and fibromyalgia through naturopathic medicine, Razi has lived the mind/body healing paradigm. Her projects uniquely capture the tradition and philosophy of naturopathy: The healing power of nature, the vital life force in every living thing and the undeniable role that science and mind/body medicine have in creating health and overcoming dis-ease. You can follow Razi on social media: Facebook at Razi Berry, Instagram at Razi.Berry and join the Love is Medicine group to explore the convergence of love and health. Look for more, and listen to more Love is Medicine podcast episodes here.
