Deep three-photon imaging of the brain in intact adult zebrafish

Behaviors emerge from activity throughout the brain, but noninvasive optical access in adult vertebrate brains is limited. We show that three-photon (3P) imaging through the head of intact adult zebrafish allows structural and functional imaging at cellular resolution throughout the telencephalon and deep into the cerebellum and optic tectum. With 3P imaging, considerable portions of the brain become noninvasively accessible from embryo to sexually mature adult in a vertebrate model. Three-photon microscopy provides access to most of the adult zebrafish brain for both structural and functional imaging, as well as to the Danionella dracula brain.