“Things that happen in real life don’t always connect directly, but we can remember the details of each event better if they form a coherent narrative,” Brendan Cohn-Sheehy of UC Davis said in a news release describing a recent study of how the human brain weaves separate and distant events into memorable stories. These peer-reviewed findings were published on September 29 in Current Biology.
“Traditionally, in neuroscience, researchers have studied the basic processes of memory involving disconnected pieces of information, whereas psychology has a tradition of studying how memory works to capture and connect events in the ‘real world,'” he added. “These two camps are starting to merge. We’re using brain imaging to get at realistic memory processes.”
Cohesive Narratives Are Easier for Our Brains to Remember
For this study, a team of researchers from Charan Ranganath’s Dynamic Memory Laboratory at UC Davis’s Center for Neuroscience used functional magnetic resonance imaging (fMRI) to peek inside the brains of 36 volunteers as they listened to a series of prerecorded fictional short stories and recalled them a day later.
The researchers created a variety of 4-minute storytelling narratives specifically for this study. Each story featured a protagonist, some side characters, and a memorable event. But the cohesiveness of different narratives was purposely varied. For example, one group of short stories had a two-part storyline that was cohesive and stuck together. On the flip side, other stories were deliberately disjointed and didn’t come together under the umbrella of a coherent overarching narrative.
When the researchers compared volunteers’ brain activity upon first hearing a short story and recalling it the following day, the fMRI neuroimages showed that their hippocampus “lit up” when learning and recounting stories with a cohesive narrative. However, if a two-part storyline wasn’t cohesive, the hippocampus didn’t activate. “[Our] results show the coherent memories being woven together,” Cohn-Sheehy said.
“When you get to the second event, you’re reaching back to the first event and embedding part of it in the new memory,” he added. “The second event is where the hippocampus is forming a connected memory.”
The hippocampus (in red) is commonly referred to as our brain’s “memory hub.”
Source: Life Science Databases/Creative Commons (CC-BY-SA-2.1-jp)
Our Hippocampus Weaves Distant Events Into a Memorable Narrative
When recalling short stories, robust hippocampal activity (or lack thereof) was directly correlated with how well a study participant remembered a short story’s narrative arc.
These findings suggest that the hippocampus doesn’t just integrate memories from overlapping experiences; it appears to play a pivotal role in constructing cohesive narratives that integrate distant events into memorable stories that are easy to retell. As the authors sum up:
“In the current study, we investigated whether the hippocampus supports a narrative-level organization for episodic memories by integrating distant events into a larger narrative. […] Furthermore, narrative coherence determined the degree to which reinstatement of hippocampal activity patterns from the second event predicted the ability to recall details about both events within a narrative.”
While other brain regions are likely involved in the process of forming cohesive narrative memories, the hippocampus appears to bring all the pieces of a story together in a way that makes it easy for storytellers to recall and retell their tales.
“In closing, even though life’s events occur at disparate times, the hippocampus can form memories that integrate events into a larger, coherent narrative. By bridging the divide between distant events, the hippocampus may support a narrative-level architecture for episodic memory,” the authors conclude.