Adult hippocampal neurogenesis shapes ideomotor action control in mice.

Humans select and learn goal-directed actions through the anticipation of their outcomes. While this ideomotor principle is well established in humans, its biological instantiation and relevance for organizing naturalistic behavior remain unclear, including its neurobiological substrates such as hippocampal plasticity. Here, we leverage high-resolution, continuous behavioral tracking in mice across a month-long series of automated learning tasks to test whether ideomotor principles generalize to naturalistic behavior and how they relate to adult hippocampal neurogenesis. Mice lived in a shared enriched environment and engaged in self-initiated learning tasks, allowing us to quantify how action-outcome associations are formed, maintained, and updated. Despite identical genetic background and environment, animals showed stable individual differences in how these associations were organized. These differences correlated with levels of adult hippocampal neurogenesis: higher neurogenesis was associated with broader, more variable exploration and greater flexibility in updating action-outcome relations, whereas lower neurogenesis was linked to more rigid behavior. Together, these findings link ideomotor theory to a cellular plasticity mechanism supporting flexible action control.