The advance: scientists mapped all 523 million neural connections in one cubic millimeter of mouse brain tissue – covering a total of over 200,000 brain cells.

The advance: scientists mapped all 523 million neural connections in one cubic millimeter of mouse brain tissue – covering a total of over 200,000 brain cells. They did it by very thinly slicing the tissue and photographing each slice at a time (which I believe is a very longstanding technique), and then training an image recognition algorithm to detect neurons in each slice, stitch them together into 3D representations, and detect connections between them. This "Machine Intelligence from Cortical Networks" project (MICrONS) was led by researchers at Princeton, Baylor, and the Allen Institute for Brain Science. Sadly, the NIH program funding this research has been cut by 60% in the last two years.