New research clarifies how the brain goes to great lengths to process and remember everyday events.
Researchers used functional MRI scanners to monitor the brains of subjects watching short videos of scenes that could have come from real life. These included people working on laptops in a cafe or shopping in a grocery store.
“They were very ordinary scenes,” says Zachariah Reagh, an assistant professor of psychological and brain sciences at Washington University in St. Louis. “No car chases or anything.”
The research subjects then immediately described the scenes with as much detail as they could muster. The mundane snippets led to intriguing findings, including that different parts of the brain worked together to understand and remember a situation.
Networks in the front part of the temporal lobe, a region of the brain long known to play an important role in memory, focused on the subject regardless of their surroundings. But the posterior medial network, which involves the parietal lobe toward the back of the brain, paid more attention to the environment. Those networks then sent information to the hippocampus, Reagh explains, which combined the signals to create a cohesive scene.
Researchers had previously used very simple objects and scenarios—such as a picture of an apple on a beach—to study the different building blocks of memories, Reagh says. But life isn’t so simple, he says. “I wondered if anyone had done these types of studies with dynamic real-word situations and, shockingly, the answer was no.”
The new study in Nature Communications suggests that the brain makes mental sketches of people that can be transposed from one location to another, much like an animator can copy and paste a character into different scenes. “It may not seem intuitive that your brain can create a sketch of a family member that it moves from place to place, but it’s very efficient,” he says.
Some subjects could recall the scenes in the café and grocery store more completely and accurately than others. Reagh and coauthor Charan Ranganath of the University of California, Davis, found that those with the clearest memories used the same neural patterns when recalling scenes that they used while watching the clips. “The more you can bring those patterns back online while describing an event, the better your overall memory,” he says.
At this time, Reagh says, it’s unclear why some people seem more adept than others at reproducing the thought patterns needed to access memory. But it’s clear that many things can get in the way. “A lot can go wrong when you try to retrieve a memory,” he says.
Even memories that seem crisp and vivid may not actually reflect reality. “I tell my students that your memory is not a video camera. It doesn’t give you a perfect representation of what happened. Your brain is telling you a story,” he says.
In future, Reagh plans to study the brain activity and memory of people watching more complicated stories.
