A change in behavioral state switches the pattern of motor output that underlies rhythmic head and orofacial movements

The breathing rhythm serves as a reference that paces orofacial motor actions and orchestrates active sensing. Past work reports that pacing occurs solely at a fixed phase relative to sniffing. We reëvaluated this constraint as a function of exploratory behavior. Allocentric and egocentric rotations of the head and the electromyogenic activity of the underlying motoneurons for head and orofacial movements were recorded in free-ranging rats as they searched for food. We found that a change in state from foraging to rearing is accompanied by a change in the phase of muscular activation relative to sniffing, so that pacing now occurs at one of two phases. Further, head-turning is biased such that an animal gathers a novel sample of its environment upon inhalation. In toto, the coordination of active sensing has a previously unrealized computational complexity that, in principle, can emerge from hindbrain circuits with fixed architecture and credible synaptic time-delays.