The human brain executes complex motor behaviors such as speech or running or juggling, but the specific cell types, gene expression patterns, and physiological profiles that enable these behaviors are largely unknown. As children, humans learn how to speak, a highly complex motor behavior, through imitation - a process referred to as vocal learning. The critical nature of spoken language in our culture and the prevalence of disorders that can affect speech makes it a critical behavior to study. However, studies in humans are limited due to the inaccessibility of the human brain and lack of experimental manipulations.