Memories Drift across Neurons over Time, Animal Study Suggests

The internal brain GPS changes whenever mice sail in a familiar and static environment, according to a new study by neurobiologists from the Northwestern University and the University of Illinois Urbana-Champaign. The results shed light on the fundamental mystery of how the brain treats and stores spatial memories, with implications for the understanding of scientists of memory, learning and even aging.

The memories of navigation of familiar paths are more fluid than we thought before, activating different neurons on each trip. Image credit: Vessal Zeinab.

“Our study confirms that spatial memories in the brain are not stable and fixed,” said Daniel Dombeck, professor at the University of Northwestern.

“You cannot indicate a group of neurons in the brain and say that memory is stored right there.”

“Instead, we see that memories have passed among the neurons.”

“The same experience will imply different neurons each time. It is not a sudden change, but it evolves slowly. ”

Located deeply in the temporal lobe of the brain, the hippocampus stores memories linked to space navigation.

For decades, neurobiologists have thought that the same hippocampal neurons coded memories of the same places.

Thus, the path that someone could take from their room to their kitchen should activate exactly the same sequence of neurons every midnight for a glass of water.

About 10 years ago, however, scientists imagined mouse brains while animals passed into a labyrinth.

Even if the mice crossed the same labyrinth day after day, different neurons fired each race. Scientists wondered if the results were a stroke of luck – maybe the experience of the rodent of the labyrinth has changed, with speed differences, an odor or something subtle in the environment.

To probe these questions, Professor Dombeck and his colleagues have designed an experience that gave them unprecedented control over the sensory entrance to the mouse.

The mice crossed the virtual labyrinth on treadmills, ensuring a precise speed measurement.

The labyrinth was presented on a multisensory virtual reality system previously developed by the team.

This not only controlled what animals have seen, but a cone on the nose of the mice provided identical odors for each session, controlling each possible environmental variable.

After having executed the experience several times, the results were clear: even in a highly reproducible virtual world, a group of different neurons activated each time.

The discovery confirmed that the spatial cards of the brain are intrinsically dynamic, constantly updating whatever the static of a space.

“This evidence suggests that memories are fluid,” said Professor Jason Climer at the University of Illinois Urbana-Champaign.

“This could be linked to deeper questions about the reasons why the brain can do things with modern artificial intelligence that fights, things like learning new things permanently.”

“It can also play a role in natural forgetting – an active process, often neglected, but essential for a healthy memory function.”

Although few models occur throughout the experience, the researchers have noticed a coherent factor: the most excitable neurons, which were more easily activated, have maintained more stable space memories throughout several races through the virtual labyrinth.

Since the excitability of neurons decreases with age, the observation could help scientists understand the role of aging and disease with regard to the capacity of the brain to code new memories.

“The small nucleus of stable neurons is special, and better understanding what makes them special could lead to new treatments for memory malfunction,” said Professor Climer.

“Memory deficits are the brand of brand of Alzheimer’s disease and are also a major obstacle for patients with a range of neuropsychiatric disorders such as schizophrenia.”

“By better understanding the fundamental aspects of memory such as changes over time we report in our article, we provide new targets to understand the differences in the brains of these patients and new processing strategies.”

“Understanding how the brain manages the problem of memory also has a lot to teach us about how computers and AI could be improved.”

The results were published on July 23, 2025 in the journal Nature.

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JR air conditioning and al. Hippocampal representations derive in stable multisensory environments. Naturepublished online on July 23, 2025; DOI: 10.1038 / S41586-025-09245-Y