Answering these questions will not only teach us about evolution but reveal general principles of brain circuit design and network structure. Ultimately, this knowledge will allow us to efficiently translate insights and treatments from animal models to human patients.

We approach our work by engineering cutting-edge circuit tracing and viral tools to map brains at much higher resolution and larger scales than previously possible. These tools include barcode sequencing-based tracing tools (MAPseq, BRICseq) and in situ sequencing approaches. We apply these technologies to a variety of species–including mice and humans, but also much less studied species of birds, reptiles, amphibians, and even sharks–and compare and contrast across them. This process allows us to infer the most likely evolutionary histories of individual brain circuits and of entire networks. Concrete hypotheses are then tested by developmental perturbations to live up to the spirit of “What I cannot create, I do not understand.”