3D scans revealed a section of a mouse's brain the size of a grain of sand (6 photos)
A groundbreaking study has provided the most detailed map of the mammalian brain to date. The 3D diagram shows more than three kilometers of neural connections, about 100,000 nerve cells and about 500 million synapses - all in a fragment of mouse brain no bigger than a grain of sand. 
Dr. Clay Reed, director of the Allen Institute for Brain Science in Seattle, said: “There’s an amazing world of connections in this little piece of brain, with rules that we’re just beginning to understand.”
The scientists recorded neural activity in a section of the visual cortex while the mouse watched a YouTube video. They then took a cubic millimeter of the brain and divided it into 25,000 thin layers, each just 1/400th the width of a human hair, and scanned them with powerful electron microscopes. The images were then stitched together and a 3D model was created using artificial intelligence. The resulting image shows not only the structure, but also how the brain cells interact with each other. 
Dr. Forrest Coleman noted: "By studying the cerebral cortex of mice, we can come to a deeper and more accurate understanding of the functioning of our own brains."
His team believes that being able to map and study the brain's internal structure at a deep level will open up new horizons for understanding and treating neurological diseases such as Alzheimer's, Parkinson's and autism. 
"Just like people use Google Maps to find the best route from point A to point B, or even to see if a route even exists, a detailed map of the brain can show whether two neurons are connected and where those connections are made," Coleman explained. 
Nuno Macarico da Costa, a researcher at the Allen Institute, said one of the interesting results of this project is an understanding of “how beautiful our brains are.”
“When you look at these neurons, you realize their detail and scale, and it evokes a sense of awe.” 
