Dynamically Updated Task Rules Reshape Sensory Processing Across Cortical Hierarchies of the Posterior Parietal Cortex and Primary Auditory Cortex.

Accumulating evidence suggests that cognitive factors such as rules and attention can modulate sensory processing through top-down influences. However, the neural mechanisms transforming cross-modal inputs into rule-guided perceptions remain unclear. Therefore, in this study, we recorded neuronal activity in the posterior parietal cortex (PPC) and primary auditory cortex (A1) of rats during an audiovisual rule-switching task to investigate how rules are dynamically encoded and modulate sensory processing. By tracking the dynamic neural encoding of internally estimated task rules on a trial-by-trial basis, our single-neuron analyses suggested that the PPC may proactively represent task rules before decision-making, whereas A1 may contribute to monitoring auditory-task performance by enhancing rule-related signals following errors. Both regions showed a preferential representation of conflicting rule combinations, suggesting a specialized mechanism for efficient conflict resolution. Accordingly, we dissociated stimulus-driven responses from rule-modulated responses and observed a within-trial transformation from sensory encoding to rule-weighted representations, progressing from physical features to behavioral relevance, although integration remained limited. Taken together, these results suggest that the PPC-A1 circuit dynamically encodes rules and reshapes sensory processing to implement structured computations for flexible behaviors.