Leonardo was fascinated with how brains work. So much so, he decided to cut them open to study them. One reason he might have been obsessed with brains was to help him work out his own depression. Why was he depressed? It might have been how little success he was having in Florence. So in 1482, the year he turned 30, da Vinci left Florence for Milan. He lived there for the next 17 years.

Leonardo da Vinci study of brain

Oh dear!
