Changes in perceptual sampling contribute to representational drift

Imagine your brain's visual system as a high-tech security camera that constantly records what you see. Scientists have noticed something strange over time: even when you look at the exact same picture, the "recording" your brain makes of it slowly changes. They call this representational drift.

For a long time, scientists thought this drift happened because the camera's internal wiring was slowly rusting or rewiring itself from the inside out (like old neurons changing their connections). But this paper asks a different question: What if the camera itself isn't changing, but the way we hold it is?

Here is the story of what the researchers found, using some everyday analogies:

The "Wandering Gaze" Experiment

The researchers set up a long-term experiment with 14 adults. They asked these people to look at natural pictures (like photos of landscapes or cities) over a period of 2 to 4 weeks. They did this in six different sessions, like visiting a museum six times over a month.

They used eye-tracking technology to map exactly where people looked on each photo. Think of this as drawing a "heat map" of where the eyes rested.

The Discovery:
They found that as time went on, the heat maps changed. Even though the photo was the same, the people's eyes started landing on slightly different spots.

• Analogy: Imagine you are looking at a painting of a forest. The first time you visit, you stare mostly at the big oak tree in the center. A month later, you still see the tree, but your eyes naturally drift a little more toward the bushes on the left. A month after that, you might focus slightly more on the sky.
• The Result: The longer the time gap between visits, the more different these "gaze maps" became. The drift wasn't random chaos; it was a slow, steady shift in direction.

The Computer Simulation

To see if these tiny shifts in eye movement could actually change how the brain "sees" the image, the researchers used a computer model called CORnet-S. Think of this model as a digital brain that mimics how a monkey's or human's visual system processes images.

They took the original photos and "masked" them based on where the participants' eyes had looked in Session 1, then Session 2, and so on. They fed these slightly different versions of the same photo into the digital brain.

The "Drift" in the Machine:
Even though the underlying photo was identical, the digital brain's reaction to it changed as the gaze patterns changed.

• Analogy: Imagine you are describing a house to a friend. If you only look at the front door, you describe the door. If you shift your gaze to the window, your description changes to include the glass. If you shift again to the roof, your description changes again. The house hasn't changed, but your description of it has drifted because your viewpoint shifted.
• The Result: The researchers measured the "distance" between the brain's reactions. They found that as the gaze patterns drifted further apart over time, the brain's internal representation of the image also drifted further apart. This happened at every level of the visual system, from the basic processing (like V1) to the complex understanding (like IT).

The Bottom Line

The paper concludes that representational drift doesn't necessarily mean the brain's wiring is breaking or rewiring itself.

Instead, it suggests that our brains are so sensitive that even tiny, inevitable changes in how we look at the world—like our eyes wandering slightly to a different spot on a familiar object—are enough to make our internal "mental image" of that object change over time.

In short: The camera (the brain) might be stable, but the way we hold it (our gaze) is always moving. And because of that, the picture we take in our minds is never exactly the same twice.