Memories are the brain’s map of time

The research team led by NTNU’s Nobel Laureates May-Britt and Edvard Moser, from the Kavli Institute for Systems Neuroscience, is already known for their discovery of the brain’s sense of place.

Now they have shown that the brain also weaves a tapestry of time: The brain segments and organizes events into experiences, placing unique bookmarks on them so that our lives don’t become a blurry stream, but rather a series of meaningful moments and memories we can revisit and learn from.

We live in a continuous stream of fleeting sensory information. How do we manage to select and segment this stream of reality into meaningful experiences we carry forward in life?

The NTNU researcher have found a “jumping” answer in a new study published in Science.

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A signal that never repeats

The researchers examined a part of the brain’s memory system called the lateral entorhinal cortex (LEC). This area provides important input that helps generate our sense of time during experiences and memories.

A new technology called Neuropixels has made it possible to record from thousands of brain cells in this area simultaneously.

“What we found was that the brain cells work together to create a signal that constantly drifts in a pattern that never repeats itself – not even during sleep. This drift isn’t driven by what we do or see, but is an inherent property of the network,” said Edvard Moser, professor of neuroscience at the NTNU Kavli Institute.

It is as if this brain area is hardwired specifically to capture new sensations and experiences.

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The brain creates bookmarks

“When something important, unexpected, or meaningful happens – for example, a reward, a new place, or a surprise – this signal makes a sudden jump before continuing its quiet drift. These jumps mark the beginning and end of an experience,” said Ben Kanter, first author of the study.

The researchers use beads on a string to explain how our sense of time works. Photo: Rita Elmkvist Nilsen/Kavli Institute, edited by Nina Tveter/NTNU SHOW MORE

The researchers use the analogy of beads on a string to illustrate how our sense of time works. The string represents our subjective experience of time, which usually drifts smoothly forward. But when something important happens, the signal jumps. Edvard Moser demonstrates this by lifting the string upwards, and May-Britt attaches a paperclip at that spot. The paperclip marks the start of a new experience – a kind of bookmark in the brain.

After that, the sense of time continues its quiet drift, with event after event threaded onto the string in the correct order, like beads on a necklace. In this way, the jumps divide the continuous flow of sensory information into distinct and meaningful experiences, organised in the sequence they actually occurred.

“These jumps give each experience a unique neural signature – a bookmark, like a barcode in the brain – making it possible to store experiences as memories and retrieve them later,” Kanter said.

Here we see Kiki the rat’s sense of time jump into the air when the rat finds the treat Ben has hidden for her. This was a memorable experience. Illustration: Ben Kanter, Kavli Institute

Time flips our memories

The study also explains why time feels so different in the moment compared to in memory.

“A boring hour can feel long while it’s happening, but it leaves behind few memories and thus feels short in retrospect. When we’re having fun, time flies – it feels short in the moment, but we end up with many rich memories, making it feel as if we experienced more than the actual time would suggest,” said May-Britt Moser, professor of neuroscience at NTNU’s Kavli Institute.

“The brain doesn’t measure experienced time itself, but experiences. The more details and events we store, the richer and longer time appears in our memory,” said Edvard Moser.

In other words, it is our experiences and memories that create our sense of time.

An important piece in the Alzheimer’s puzzle

The findings may also have major implications for understanding dementia.

“Alzheimer’s disease often starts in the lateral entorhinal cortex – precisely where the sense of time is created,” said May-Britt Moser. “When the cells in the LEC die, it becomes harder to organize memories and understand the sequence of events.”

She illustrates this by picking up scissors and cutting the bead string Edvard is holding. The organizing thread of time is severed, and the beads – the events – spill out in disarray, without structure.

“Our goal is to understand how a healthy brain organizes time and memories. If we succeed, we may be able to develop methods to detect Alzheimer’s earlier and stop cell death before the disease causes too much damage,” she says.

At the K.G. Jebsen Centre for Alzheimer’s Disease, neuroscientists at Kavli are collaborating with neurologists at St. Olavs Hospital. They are already using this knowledge to develop biomarkers that can detect the disease early. The ultimate goal is clear: To solve the Alzheimer’s puzzle – and give people the chance to keep their memories and their lives intact for as long as possible.

: Neuroscientists May-Britt Moser, Ben Kanter, and Edvard Moser are happy and proud of the discovery, which has required over five years of intense work. Foto: Sophie Jessica Larson / Kavli Institute SHOW MORE

The study was carried out by Ben Kanter (first author), Christine Marie Lykken, Ignacio Polti, May-Britt Moser (senior author), and Edvard Moser (senior author) from the Moser Group at the Kavli Institute for Systems Neuroscience, NTNU.

Reference: Benjamin R. Kanter et al., Event structure sculpts neural population dynamics in the lateral entorhinal cortex. Science 388, eadr0927 (2025).  https://doi.org/10.1126/science.adr0927