A new discovery by McGill researchers reveals how we retain memories over time despite constantly changing brain activity.
Published in naturepreclinical studies have found that the brain’s internal compass is remarkably stable over time. The findings suggest that this stable sense of direction may function as a memory anchor.
“This is a long-standing mystery: If the brain’s memory structures keep changing, why do our memories remain so stable? Our results provide an explanation,” said senior author Adrian Peyras, associate professor in the Department of Neurology and Neurosurgery at McGill University and director of the Peyras Lab at The Neuro (Montreal Neurological Institute Hospital).
The internal compass, known as the head direction system, is a network of brain cells that tracks which way we are facing as we move. It also connects the hippocampus, the brain’s memory center, with other parts of the brain.
The researchers tracked the same brain cells in mice over several months using a small head-mounted microscope. They found that even when the hippocampus was reorganized, the head direction system remained structurally intact.
The researchers also found that when exploring a new space, the brain’s compass quickly sets a directional reference point, essentially deciding which way is north or south, and retains that sense of direction when revisiting the space weeks later.
These findings reveal a surprising contrast. Although the hippocampus may reorganize its activity over time, the head direction system provides a very stable basis for interpreting spatial information. ”
Adrien Peyrache, Associate Professor of Neurology and Neurosurgery, McGill University
He added that the results have implications for Alzheimer’s disease research, as feeling lost or disoriented is often one of the earliest warning signs, sometimes appearing before significant memory loss.
“Understanding how spatial stability is normally maintained could help clarify why these abilities are impaired and open new avenues for early detection and future treatment strategies,” Perrache said.
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Reference magazines:
Scromne Carrasco, S. others. (2026). Stability of the head direction system over months. nature. DOI: 10.1038/s41586-025-10096-w. https://www.nature.com/articles/s41586-025-10096-w
