Mice learn multi-step routes by memorizing subgoal locations

Animals must rapidly gather spatial information about new environments so that they can quickly reach food or safety even when direct paths are unavailable. The behavioral strategies used to implement multi-step routes to goals in naturalistic settings are unknown. Here we show that mice spontaneously learn a subgoal memory strategy while escaping to shelter or seeking food in an obstructed environment. We first investigated how mice navigate to shelter in response to threats when the direct path is blocked by a wall. Initially, mice ran straight toward the shelter and circumvented the obstacle using sensory cues. Over the course of 20 minutes, however, they switched to a spatial memory strategy to execute spatially efficient paths. Efficient escape routes were not learned by reinforcing egocentric actions or by constructing an unbiased internal map during exploration. Instead, mice used a hybrid strategy: they memorized specific subgoal locations encountered during previous running movements toward the obstacle. We then found that the same behavioral strategy is also used in a reward-seeking task. These results show that spontaneous memorization of local subgoals is a fundamental strategy by which rodents execute efficient multi-step routes to goals in novel environments.