Researchers Achieve Milestone by Mapping a Portion of a Mouse’s Brain in Unprecedented Detail, Marking a Major Advancement in Neuroscience

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The 3D brain map includes more than 200,000 cells, 523 million synapses and over two miles of axons, representing the most detailed wiring diagram of a piece of mammal brain ever constructed

Margherita Bassi
– Daily Correspondent

April 10, 2025 4:19 p.m.

In a groundbreaking achievement, a collaborative team of over 150 researchers has successfully mapped an intricate section of a mouse’s brain, disproving biologist Francis Crick’s assertion from 1979 that creating an accurate diagram of the brain’s wiring would be impossible. Their work, which focuses on a minute cubic millimeter of brain tissue, has unveiled a complex network of neuronal connections previously thought beyond reach.

Published in a series of ten studies in the Nature journals, the research is part of the Machine Intelligence from Cortical Networks (MICrONS) project. It represents the most comprehensive wiring diagram of any mammal’s brain to date, holding significant potential for advancing our understanding of neurological disorders affecting humans.

“The complexity of what we’ve uncovered is awe-inspiring, akin to gazing at the vastness of outer space,” remarkedForrest Collman, a neuroscientist from the Allen Institute and one of the lead researchers, in an interview with the Associated Press. “It highlights the intricate nature of our own biological makeup.”

The map documents over 200,000 cells, 523 million synapses (the connections between neurons) and more than two miles of axons—the extensions of neurons that transmit electrical impulses. The comprehensive dataset totals a staggering 1.6 petabytes, equating to around 22 years of continuous high-definition video, as noted in a statement from the National Institutes of Health statement.

Collman likened the brain map to “Google Maps for the brain,” providing a detailed view that not only highlights major neural pathways but also showcases the smallest connections and relationships within. “This level of detail enables scientists to determine whether two neurons are linked and pinpoint the exact nature of these connections,” he explained during a conversation with the London Times.

The Creation of a Revolutionary Brain Map

To construct the brain map, researchers utilized a genetically modified lab mouse, whose neurons illuminated when activated. The team recorded electric activity in the mouse’s visual cortex—a section of the brain crucial for processing visual information—as it viewed content from Mad Max: Fury Road, The Matrix, and the Qatsi experimental film trilogy.

Subsequently, they harvested a cubic millimeter of brain tissue, slicing it into approximately 28,000 ultra-thin layers. Each layer was meticulously photographed, and cutting-edge artificial intelligence was employed to compile the images into a 3D digital representation, integrated with the previously acquired data reflecting neural activity associated with vision.

This innovative approach allowed researchers to correlate the structural mapping of neurons with their functional roles, enhancing their understanding of the intricate connections that dictate neuronal interactions.

While past research has focused on cerebral structure or function in isolation, this study represents a significant leap in the aspiration to synergize both aspects within the same organism. “This is the largest endeavor to unify brain structure and function within a single individual mouse,” remarked Andreas Tolias, a neuroscientist from Baylor College of Medicine and a lead researcher, in an interview with Reuters.

The researchers’ findings revealed novel types of cells, established new relationships among cells, and highlighted organizational rules previously unknown, particularly among inhibitory cells, which dampen brain activity. Their investigation provides significant insights into how neuronal connectivity can influence cognitive functions and how alterations in this network may relate to conditions such as Alzheimer’s, autism, Parkinson’s disease, and schizophrenia.

“Having a detailed circuit diagram is like having a roadmap to repair a malfunctioning radio,” noted Nuno da Costa, a biologist at the Allen Institute and a project leader. He emphasized that this detailed mapping could enable comparisons between healthy and diseased brain wiring in the future.

Considering the similarities between mouse brains and human brains, findings from this research could offer valuable insights relevant to human neural circuitry. As Sebastian Seung, a Princeton University neuroscientist involved with the MICrONS project, contends, such information might prompt the development of more precise medications to mitigate side effects in psychological treatment.

In the words of Davi Bock, a neuroscientist from the University of Vermont and an observer of this study, the achievement signifies a “milestone” in neuroscience. Bock, affiliated with another project that mapped an entire adult fruit fly brain last year, expressed optimism about the feasibility of mapping an entire mouse brain in the near future. “It’s entirely achievable, and I believe it is worth pursuing,” he remarked.

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