Fig. 4.

Pavlovian responses. In this schematic, we have added a hierarchical level that incorporates exteroceptive predictions (here, of a ringing bell) into its model of state transitions. This higher-level construct represents the sound of a bell that portends interoceptive changes that induce autonomic reflexes (or unconditioned responses). Because the highest level now provides predictions in the exteroceptive and interoceptive domain, it enables perceptual inference to elicit autonomic responses, providing interoceptive predictions that can be fulfilled by smooth muscle reflexes. Here, the agent's model of the world involves a bell ringing that causes gustatory events that induce salivation. Optimizing expectations about auditory objects corresponds to predictive coding of auditory input and the perception of bell ringing; while descending interoceptive predictions cancel gustatory prediction error and descending predictions about the state of smooth muscle reflexively elicit salivation.