The ability to recall not just what happened, but when and where, is fundamental to human experience. But for the over 55 million people worldwide living with dementia, including Alzheimer’s disease, these anchors to reality – time and place – often begin to fray. Now, research from the University of Oslo suggests these two seemingly distinct perceptions are deeply intertwined in the brain, potentially offering new insights into the neurological roots of these devastating conditions. The number of people living with dementia is projected to triple by 2050, according to the Alzheimer’s Association, making understanding the brain’s mechanisms for encoding time and space a critical area of study.
For decades, scientists have understood the hippocampus plays a key role in spatial memory – our internal GPS. But a growing body of evidence suggests other brain regions are also involved in tracking both time, and location. Researchers are increasingly focused on how the brain integrates sensory information to create a cohesive sense of episodic memory, the recollection of past events. “All memories are made up of different components. You don’t just remember what you had for dinner yesterday, but also the time and place,” explains Koen Vervaeke, a Professor at the University of Oslo. “We often perceive of time and space as separate categories, a distinction created by philosophers and physicists that is incredibly practical for organizing our lives. But our brain cells don’t notice it that way.”
The Retrosplenial Cortex: A Bridge Between Time and Space
Vervaeke and his team at the Institute of Basic Medical Sciences focused their investigation on the retrosplenial cortex, an area located near the hippocampus. While previously known for its role in linking memories to place, the researchers hypothesized it also contributes to our perception of time. To test this, they designed a behavioral experiment using mice, recently published in Cell Reports. DOI: 10.1016/j.celrep.2025.115363
The task involved presenting the mice with a sequence of scents – banana followed by mint, for example – separated by a five-second pause. Mice were rewarded for correctly identifying when the scents were different, and required to remain still when presented with the same scent twice. Initially, the mice struggled with the timing, but after a week of training, they consistently mastered the challenge. “They learned to use that five-second silence to hold the first memory in their minds, waiting to see if the next scent would match or change,” Vervaeke explains.
A Shared “Neural Script” for Navigating Reality
Using microscopic imaging, the researchers monitored nerve cell activity in the retrosplenial cortex as the mice performed the task. They observed two distinct groups of cells at function. One group responded specifically to the presented scents, while the second group exhibited a sequential firing pattern during the five-second pause. This pattern, Vervaeke describes, functioned like a “relay race,” with one cell activating the next, effectively holding the memory of the first scent in mind.
The most striking finding was the similarity in neural activity whether the mice were engaged in the scent-based memory task or physically navigating a space. “We found that the sequence of neuronal activity in the retrosplenial cortex looks almost identical whether a mouse is physically running through a room or simply holding a memory in its mind for five seconds,” Vervaeke said. This suggests the retrosplenial cortex utilizes a common “neural script” for both spatial and temporal processing, blurring the lines between where and when in the brain’s internal representation of reality.
Implications for Alzheimer’s Disease and Our Understanding of Perception
This discovery sheds light on why both a sense of time and place are often impaired in Alzheimer’s disease. Damage to the neural networks involved in this shared processing can disrupt the brain’s ability to anchor experiences in both time and space. The Alzheimer’s Association estimates that more than 6.7 million Americans are living with Alzheimer’s disease in 2024. Alzheimer’s Association Facts and Figures
Beyond the clinical implications, the research challenges our conventional understanding of time and space. While we typically perceive these as distinct dimensions, the brain appears to operate differently. “This work also challenges how we perceive the world around us,” Vervaeke notes. “While we use the concepts of time and space to organize our lives, this distinction is largely a human construct.” Interestingly, some contemporary theories in physics are also moving away from viewing time and space as fundamental building blocks of the universe, suggesting a potential parallel between the brain’s internal wiring and the deeper structure of reality.
“We still have an enormous amount to learn about how a healthy brain functions,” Vervaeke concludes. “We see nearly impossible to repair a car if you don’t first understand how the engine works when it’s running smoothly. Similarly, we must understand the ‘blueprints’ of a healthy brain, how it builds and stores these episodic memories, before we can truly grasp what goes wrong in dementia. These findings bring us one step closer.” The University of Oslo team plans to continue investigating the neural mechanisms underlying episodic memory, with the goal of identifying potential therapeutic targets for preventing or slowing the progression of neurodegenerative diseases.
Disclaimer: This article provides information for general knowledge and informational purposes only, and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.
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