Prefrontal cortex represents spontaneous behavior as a succession of tasks

Animals compose low-level actions in the service of high-level goals. Prefrontal cortex is essential for this organization when the goals are externally imposed, as in tasks where reward contingencies switch over time. Here we asked if it plays a similar role during spontaneous exploratory behaviors in the mouse. Using a hierarchical model, we identify stable patterns of action selection that capture emergent ‘task-states’ like wall following, object investigation or social interaction. These states align with distinct epochs of activity in medial prefrontal cortex (mPFC) – a coincidence that cannot be explained by encoding of low-level kinematics. Within each state, mPFC preferentially encodes task-relevant features of the external environment; and when mPFC is lesioned, the hierarchical differentiation of behavior diminishes, leading to a contraction of behavioral timescales. This work identifies a core timescale at which behavior and neural activity are organized in mice and suggests a general role for mPFC in the representation and regulation of high-level behavioral states.