Health

Scientists Map Brain’s 'Mileage Clock' for Distance Tracking

Published SEP 19 2025

Story

Above: A doctor looking at an MRI scanner monitor. Image credit: Monty Rakusen/Getty Images

The Facts

Researchers at the University of St. Andrews trained rats to run set distances in rectangular arenas and recorded brain activity in the medial entorhinal cortex. They found that grid cells fired in a pattern like a “mileage clock,” ticking about every 30 centimeters traveled.
University of St. Andrews
iScience: Cell Press Journal
BBC News
When the arena was reshaped into a trapezoid, the regular firing pattern of grid cells became distorted. As a result, the rats consistently misjudged distances, stopping short of the reward point because their internal mileage clock was disrupted.
iScience: Cell Press Journal
The 5krunner
Human volunteers took part in a scaled-up version of the experiment inside an arena measuring 12.2 meters long and 6.1 meters wide. Like rats, people estimated distances accurately in rectangular environments but made systematic errors when the walls were moved.
iScience: Cell Press Journal
Aanbiedingstudie.n
The study, published in Current Biology, is the first to show a direct connection between grid cell firing and the ability to correctly estimate distance in both rats and humans, providing new insight into how the brain’s internal mileage counter works.
BBC News
University of St. Andrews
Researchers noted that greater disruption of the grid cell signal correlated with higher levels of error in judging distances. The less regular the brain’s ticking pattern, the more mistakes participants made in estimating how far they had traveled.
iScience: Cell Press Journal
BBC News
The medial entorhinal cortex, home to these distance-tracking cells, is among the first brain regions affected by Alzheimer’s disease. Scientists suggest the findings could help develop new diagnostic tools based on distance estimation tasks.
University of St. Andrews
iScience: Cell Press Journal

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The Spin

Narrative A

This breakthrough explains why navigation often fails in poor visibility. The brain relies on an internal "mileage clock," a rhythmic firing of grid cells that acts like a biological odometer. When visual cues vanish in fog or darkness, that signal becomes irregular, causing people to misjudge distance. Tests in both rats and humans reveal the same underlying system, showing a shared mechanism for spatial navigation across species.

University of St. Andrews

Narrative B

The discovery of the brain’s mileage clock may transform Alzheimer’s detection. Grid cells in the medial entorhinal cortex, among the first regions affected, fire in regular patterns that allow accurate distance estimation. When this signal is disrupted, errors emerge, offering a potential early marker of disease. Researchers say navigation-based tasks could serve as “early warning” tests, opening new pathways for diagnosis and future treatment strategies.

Independent