A discovery by McGill University researchers sheds light on how memories can endure over time, even as brain activity is constantly in flux. Published in Nature, the preclinical study found that the brain’s internal compass remains remarkably stable, suggesting that this persistent sense of direction may act as a reliable anchor for memory.
“This has been a long-standing puzzle: if the brain’s memory systems are continually changing, how do our memories remain so stable?” said senior author Adrien Peyrache, Associate Professor in the Department of Neurology and Neurosurgery at McGill and director of the Peyrache Lab at The Neuro (Montreal Neurological Institute-Hospital). The brain’s internal compass, known as the head-direction system, is a network of neurons that tracks orientation as we move and links the hippocampus—the brain’s key memory centre—to broader neural circuits.
Using miniature head-mounted microscopes, the researchers followed the same brain cells in mice over several months. They found that while the hippocampus reorganised its activity over time, the head-direction system remained structurally stable. When mice explored a new environment, this internal compass quickly established a directional reference point—effectively defining “north” and “south”—and preserved that orientation when the space was revisited weeks later.
“These findings reveal a striking contrast,” Peyrache noted. “While the hippocampus may reorganise, the head-direction system provides a stable foundation for interpreting spatial information.” The results may also have implications for Alzheimer’s disease, as disorientation is often one of the earliest warning signs. Understanding how spatial stability is normally maintained could help explain why these abilities deteriorate and support new approaches to early detection and future therapies.
More information: Sofia Skromne Carrasco et al, Months-long stability of the head-direction system, Nature. DOI: 10.1038/s41586-025-10096-w
Journal information: Nature Provided by McGill University
