Your wedding day. The day your child was born. The death of your parents. Moving into your first home. A terrible accident. Watching your child graduate college.
Of course, you remember every detail of those life-changing, emotional events.
But do you? And what did you learn from those highly charged events that impacts your future choices?
"The things that stand out in our life history are not the mundane things like what we ate for lunch on Tuesday, right?" says Elizabeth Phelps '84, the Pershing Square Professor of Human Neuroscience at Harvard University. "The memories that persist are the special ones, milestone events and tragedies."
From the purview of the sometimes intertwining disciplines of psychology and neurology, Phelps, has spent her career unpacking the impact of emotion on memory and cognition as well as how memories relate to anxiety, depression, and other psychological disorders.
That work has earned her impressive accolades. She is a fellow of the American Association for the Advancement of Science, the Society for Experimental Psychology, and the American Academy of Arts and Sciences, among many honors.
Memory has three stages: encoding, when our brains convert a sensory input into a memory as we experience it; storage, when the encoded information is held in the brain over time; and retrieval, when we bring that stored information back into our conscious awareness.
Throughout the process, we are more likely to remember negative experiences.
"During storage, when stress hormones are aroused, they cause the amygdala to lay down memories more strongly," Phelps says.
It makes perfect evolutionary sense that a past scary experience prompts apprehension and fear later, she adds. "When something's threatening to me, I'm going to remember it a little bit easier and stronger than learning that something's safe for me."
Phelps examines the brain systems involved in reducing threat responses based on traumatic memories, aiming to gain understanding about how they influence behavior.
But sometimes, long after the threat is gone, the now-unnecessary coping behaviors remain and become a psychopathology, like an anxiety disorder. While this understanding could one day lead to treatments for anxiety disorders for those dealing with long-term stress, Phelps and her collaborators emphasize their work is basic science.
"It would be disingenuous and harmful to suggest we have come up with better treatments," Phelps says. "We are doing the basic science that we hope can lead there."
The lifelong work of the Bethesda, Maryland, native has strong roots at OWU. She came to Delaware without a clear career path but flourished in athletics, playing volleyball and running track—making All- American three times in heptathlon. A philosophy class piqued her interest in psychology, and that led to an introduction to Harry Bahrick, the now-retired OWU psychology professor renowned for his pioneering work on long-term memory. He became her undergraduate advisor, and she worked in his lab.
In December, Phelps returned to Delaware to attend Bahrick's 100th birthday party.
"There's no question—Harry got me not just into research, but the study of memory," she says. "It was a fantastic launching pad."
It was a fantastic launching pad.
on her years at OWU
Unlike other researchers who focused on shortterm memories that could be measured in a lab situation, Bahrick investigated what information, like words learned in a high school Spanish class, could be retrieved decades later.
"What happens when you get outside the lab and it's 25 years from now?" she asked. "What do you remember?"
While memories tend to drop off quickly, there are tipping points. "If you remember something a week later, you're more likely to remember it two weeks later and then three weeks later," she says. "If you remember something for five years, you've got it for the next 20 or so after that."
In graduate school at Princeton University, she focused on the intersection of neurobiology and psychology as it relates to memory, centering her lab work on memorization of lists of words or pictures. But Bahrick's exploration of long-term memory in everyday life outside the lab impacted her next steps. She realized her own meaningful, emotionally-based memories are the ones she held on to, inspiring her to dive deep into understanding the connection between emotion and memory.
Then, as a postdoc, she had two goals— studying emotion and memory and diving into the neurobiology of those processes. That led her to Joe LeDoux, whose New York University lab focused on rodents and memory, but Phelps was not particularly interested in studying animals. "I can't ask a rodent what they remember," she says.
A year later she moved to Yale University to set up her own lab, but her collaborations with LeDoux continued for decades, and she eventually returned to NYU. Their work together looks at how we learn fear, how to change those memories, and how emotions change memories each time they're recalled.
"Many people in the field have described the collaboration between Liz and me over that long period of time as a prime example of how to interact when you're studying both animals and humans," LeDoux, now retired, says. "She was a wonderful collaborator, and we just had a great time."
Together, their work took two paths.
One looks at how we remember episodes of our life and if emotions change those memories. For example, all Americans of a certain age remember where they were the morning of Sept. 11, 2001. It's what Phelps calls a "flashbulb memory," a snapshot that our brains take of a particular emotional moment in time. The 9-11 tragedy was a unique opportunity to study a highly charged event and the impact of strong emotion on memory.
"One of the things we found was that people are very confident their memories are right, but when we ask them the details of their memories, they change about 40% within a year," she adds. "But they're 100% sure they're right."
Long-term and short-term stress impacts how we store memories and changes our ability to retrieve them.
"If it's 9-11 and you're taking an exam, it's not going to be ideal," she adds. "It's going to be harder for you to focus, because stress will impair the prefrontal cortex."
And intense, chronic stress can impair our ability to remember things. "Chronic stress can actually impair the hippocampus, which is important in memory formation," she says.
Often, exposure therapy, a type of cognitive behavioral therapy, is used for treating anxiety disorders by asking the patient to re-experience the stressor many times. "Eventually you should learn that those memories are safe, and it will reduce your threat reactions," Phelps says.
Research shows that it works for about 50% of patients, she says, but 40% will relapse at some point.
"We know that those techniques essentially inhibit the prefrontal cortex to stop the threat response, but it doesn't actually change the underlying representation of the threat itself," she says. "So, this inhibition can fail."
Are there other work-arounds? That's the focus of the other path of her work with LeDoux—how to change those fear-filled memories once they no longer serve us.
"It's one thing to see fear in a mouse, but if you can't translate it into a human, you've gotten nowhere," says B.J. Casey, a neuroscience professor at Barnard College of Columbia University and Phelps collaborator. "And Liz has just been at the frontier of doing this."
Reconsolidation is the disruption of the memory storage process before the information is fully stored. For instance, people who have concussions often don't remember the cause. It can also happen at certain key moments later in retrieving a memory.
Phelps says that about 20 years ago, a member of LeDoux's lab discovered that when a memory is retrieved and it has to be stored again, that might create a new moment to disrupt, or change, the memory.
"Can we take advantage of that time window when it is malleable, and change it going forward," Phelps asks. "Can we change the emotional quality, modifying it so it is no longer threatening?"
Perhaps the findings could one day lead to improvements in exposure therapy. Barnard's Casey works with adolescents "who have a hard time letting go. They are more vigilant," she adds, because their prefrontal cortex, which helps regulate emotions, is less developed.
She is looking at how to find the sweet spot in therapy to change fearful memories that no longer serve, Casey says. "That builds directly on Liz's work."
Colleagues describe Phelps as "a powerhouse" who has championed other women who are scientists. "She's hardcore," Casey says. "She's powerful. She could be intimidating. But when she wants to see something done, it's going to get done."
After six years at Harvard and decades studying emotion and memory, Phelps plans to continue on this path.
"I'm very happy at Harvard," she says. "I feel very lucky that I found something I really enjoy doing in my life. In the scheme of things, this is an amazing job."
Written by Julianne Hill, a freelance writer and producer based in Chicago.