A major goal of neuroscience is to understand the neural circuits underlying animal behavior. Many contemporary studies focus on behavioral tasks which do not reflect realistic conditions, such as mapping an arbitrary sensory stimulus to motor output. Given that the brain evolved within the context of the natural environment, it is more likely that these circuits were optimized for naturalistic behaviors such as avoiding predators, hunting, and social interactions with conspecifics. Many of

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... e naturalistic behaviors predate the great expansion of the neocortex in mammals, as they are crucial for the survival of any animal. Using a mutant mouse model and surgical techniques, we show that the evolutionarily ancient subcortical circuits of mice are sufficient for sensory processing, stimulus discrimination, and exhibiting robust innate defensive behaviors in a predator avoidance assay. Furthermore, these animals are capable of navigating a complex labyrinth, which challenges long-held beliefs that learning and memory require the neocortex and the hippocampus. Our results emphasize the significant capacity of subcortical circuits in behaviors necessary for survival and illustrate the importance of using naturalistic behaviors to probe brain function.