How do animals move in the dark?

TThe body may know where we are going before our eyes do, building maps of the world based on a kind of internal GPS rather than landmarks or other visual cues. This process, known as path integration, allows the brain to track your every move and shift, updating your location in time and space, even in the dark.

Certain neurons in the hippocampus known as place cells are central to this process in the brain. They are active in specific locations regardless of whether the animal can see its surroundings or not, relying on internal signals to determine which locations are of particular interest. Working together, neurons fire patterns that track the passage of time and distance during movement.

A team of scientists from the Florida Max Planck Institute for Neuroscience recently revealed new details about how these internal maps work: Instead of using a single internal clock, the brain uses two interacting sets of excitatory and inhibitory neurons in the hippocampus. The researchers published their results Results in Nature Communications.

Scientists have long known that the hippocampus helps animals navigate, and that certain neurons fire in specific places they visit. “However, in environments full of sights, sounds and smells, it is difficult to know whether these neurons are responding to those sensory signals or to the position of the animal itself,” explained Yingxu Wang, a neuroscientist at the Florida Max Planck Institute for Neuroscience and a co-author of the paper, in statement.

Read more: “The woman who got lost at home“

To cut through the noise, the researchers worked with mice, whose hippocampal circuits can be recorded and manipulated with great precision. They first trained mice to run fixed distances along a virtual linear path to reach the reward. The path did not include any clear landmarks or visual cues, forcing the mice to rely on internal estimates of distance and time. While the mice were going through the training session, the researchers recorded activity across hundreds of neurons. They then used light to manipulate some of the inhibitory circuits and test how those perturbations affected the animals’ sense of time and distance.

Once they collected the recordings, two distinct patterns emerged. A group of excitatory neurons called PyrUp were activated all at once at the onset of movement and then gradually faded away, each at its own pace. Taken together, this graded activity appears to give the brain something to measure, allowing it to know how far the animal has traveled in the journey. Another group, known as PyrDown excitatory neurons, showed the opposite pattern, calming down at the beginning of the movement and then gradually returning to activity. This activity helped mark the beginning of a new journey, preventing the brain from confusing one journey with another.

From there, the team used light to silence two types of inhibitory neurons in the brain: SST neurons, which help stabilize the brain’s internal timing signals, and PV neurons, which act as a kind of reset button. When these neurons were silenced, the mice misjudged distance or time without changing their running speed. This discovery strengthened the idea that PyrUp and PyrDown neurons encode internal measures of time and space, rather than movement itself. Additional control experiments confirmed that the effects were not due to motor problems, visual deficits, or altered reward expectations.

If similar patterns are found in people, they may help explain why people with Alzheimer’s disease and other types of dementia often become disoriented even in familiar places — and could point to new therapeutic targets for restoring that lost sense of who we are.

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Main image: Rodmer Zuerfer/Shutterstock

• Christine French

  Posted on December 17, 2025

  Christine French is associate editor at Nautilus. She has worked in science journalism since 2013, reporting and writing articles and news stories for publications such as wired, back channel, edge, and New York Magazine. She earned a master’s degree in science journalism from Columbia University.