A communication subspace relays context-dependent actions from human prefrontal to motor cortex

Adaptive behavior relies on the ability to translate abstract rules and goals into actions suited to the current context. Neural population activity in the prefrontal cortex (PFC) has been proposed to support such flexible computations through high-dimensional dynamics, whereas activity in the primary motor cortex (M1) is related more directly to movement execution. How contextual representations in PFC are transformed into ensuing action plans within M1 remains unknown. Previous work suggests that low-dimensional coding subspaces might organize interareal communication, but direct evidence for such population-level communication mechanisms in humans is lacking. Here we use intracranial recordings from human PFC and M1 to identify a communication subspace embedded within high-dimensional PFC activity, that selectively relays behaviorally relevant information at the single-trial level. Activity in this subspace predicts context-dependent action more strongly than either region, revealing a fundamental coding principle by which coordinated interareal population dynamics filter and relay predictive information to guide context-dependent actions.