Internal compass helps the brain keep memories stable during change

A new discovery by McGill researchers sheds light on how we retain memories over time, even though brain activity is constantly changing.

Published in Nature, the preclinical study found the brain's internal compass remains remarkably stable over time. The findings suggest this steady sense of direction may act as an anchor for memory.

"This is a long-standing puzzle: if the brain's memory structures keep shifting, how do our memories remain so stable? Our results offer an explanation," said senior author Adrien Peyrache, Associate Professor at the Department of Neurology and Neurosurgery at McGill and director the Peyrache 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 links the brain's memory centre, the hippocampus, to the rest of the brain.

Using miniature head-mounted microscopes, researchers tracked the same brain cells in mice over several months. They found the head-direction system remained structurally intact, even as the hippocampus reorganized.

The team also found that when a new space was explored, the brain's compass quickly set a directional reference point, essentially deciding what counted as north or south, and preserved that sense of direction when the space was revisited weeks later.

These findings reveal a surprising contrast. While the hippocampus may reorganize its activity over time, the head-direction system provides a highly stable foundation for interpreting spatial information."

Adrien Peyrache, Associate Professor, Department of Neurology and Neurosurgery, McGill University

The results have implications for research into Alzheimer's disease, he added, as getting lost or feeling disoriented is often one of the earliest warning signs, sometimes appearing before significant memory loss.

"Understanding how spatial stability is normally maintained may help clarify why these abilities deteriorate, opening new avenues for early detection and future therapeutic strategies," said Peyrache.