After making a mouse watch 'The Matrix', scientists create the largest 3D brain map ever
Produced by Tarun MIshra
Produced by Tarun MIshra
Scientists have mapped the largest connectome — a 3D chart of brain cells and their links — by analysing a cubic millimetre of a mouse’s brain, roughly the size of a grain of sand. The dataset includes 200,000 cells and 523 million synaptic connections.
The project was conducted by the MICrONS consortium, a group of more than 150 researchers across US institutions. Their findings were published in a series of studies in Nature on 9 April 2025.
Neural activity was recorded in a live, genetically modified mouse while it viewed visual stimuli, including clips from The Matrix, Mad Max: Fury Road, and Star Wars: Episode VII. These recordings came from the occipital lobe, the brain’s visual processing centre.
Following the recordings, the mouse brain was imaged using an electron microscope. A machine learning algorithm then traced cells and their structures, producing the final 3D map. The system also identified different types of brain cells based on their physical features.
The connectome revealed how inhibitory neurons target distant excitatory cells with precision. This suggests these inhibitory cells may play a more targeted role than previously thought, beyond just localised suppression.
The connectome dataset has been made publicly available, allowing other researchers to explore the data. It is expected to support ongoing studies in brain function and disorders linked to neural circuit dysfunctions, such as Alzheimer’s disease and multiple sclerosis.
Researchers plan to expand the mapping to the entire mouse brain under the U.S. NIH BRAIN Initiative. However, future progress may be affected by recent funding cuts, including a $278 million reduction last year.