Scientists have developed a method to recreate short videos based solely on brain activity recorded from mice, effectively allowing researchers to see what the animals were visually experiencing. This study, led by researchers at University College London (UCL), provides a new way to explore how the brain processes visual information and transforms it into an internal representation of the world. The findings, published in the journal eLife, could advance understanding of visual perception across species and may one day help scientists compare how different animals perceive their environments. For years, researchers have been trying to understand how the brain interprets visual signals from the eyes. In human studies, scientists have used functional magnetic resonance imaging (fMRI) to record brain activity while people watch images or movies, then used that data to attempt to reconstruct visual information at a detailed level. The new approach, however, uses recordings from individual brain cells in mice. These single-cell measurements offer a more precise view of how visual information is encoded in the brain compared to the broader signals captured by fMRI. Using activity recorded from the visual cortex of mice, the team successfully generated high-quality reconstructions of videos that had been shown to the animals. Lead author Dr. Joel Bauer from the Sainsbury Wellcome Centre at UCL explained, "We wanted a better way to investigate how the brain interprets what we see. Current methods aren't easily adaptable to new situations, so we developed a method that can capture what the brain represents and compare it to reality." The researchers are particularly interested in how the brain's internal representation of the world differs from the actual physical environment. To reconstruct the movies, the team used a dynamic neural encoding model originally developed for the 2023 Sensorium Competition. This model predicts how individual neurons respond when mice watch movies, factoring in movements and changes in pupil size. The UCL researchers refined this model using the same dataset. They first calculated how neurons would behave if the mouse had been looking at a blank screen, then compared that prediction with actual neural activity recorded while the mouse watched a movie. Using an algorithm, they adjusted the pixels of an initially blank video until it closely resembled the original. After training the model, they tested it with a video that had not been in the training data, and the system successfully reconstructed a 10-second clip of an unseen scene. While the results are promising, the researchers note that there is still room for improvement in terms of image resolution and the portion of the visual scene that can be reconstructed. Future studies aim to collect more detailed data to enable sharper and more complete reconstructions. Ultimately, the team hopes to use this technique to explore a deeper question: how much does the brain's internal representation of the world differ from reality? Vision is not a simple recording process; the brain continuously interprets, filters, and modifies sensory input. Understanding these changes could reveal key insights into perception. Dr. Bauer concluded, "The brain's representation of the world isn't perfect. It skews and warps information, but this is not an error—it's a feature that reflects how our minds interpret and enhance sensory experiences."