It’s the largest and most-intricate map to date of the neural activity and connections in a mammal’s brain. Scientists used AI to track the equivalent of 4,000 kilometers of neural cables packed into a brain segment the size of a grain of sand. To carry out this task by hand would have taken decades, if not longer. The World’s Carol Hills spoke with project lead Nuno da Costa of the Allen Institute about the significance of this achievement, and what it might tell us about our own brains.