I don't really know what a normal brain looks like. A sidebar (middlebar?) about halfway through the article describes what we're looking at: The trauma of rep

I don't really know what a normal brain looks like. A sidebar (middlebar?) about halfway through the article describes what we're looking at: The trauma of repetitive blows to the head triggers degeneration in brain tissue, including the buildup of an abnormal protein called tau. Thin slices of tissue are dyed and the tau shows up as these darker areas.