Figure 7. The whisking rhythm generator circuit in the broader context of orofacial behaviors.

(a) Summary of evidence for a rhythm generator in the vibrissa zone of the intermediate band of the reticular formation (IRt; gray). This region contains units that fire in phase with all whisking events in freely behaving animals as well as when whisking is induced by microinjection of kainic acid. This region also contains cells that project to the facial nucleus, and lesions of this area severely disable whisking on the ipsilateral side.

(b) Model of the medullary circuitry that generates whisking in coordination with breathing.

(c) Summary of all premotor nuclei (yellow) that are known to receive rhythmic drive from the preBötzinger complex (orange), or conjectured to receive input based on anatomical projections, along with a potential resetting circuit (brown). The nuclei subserve shared oral facial behaviors, as demonstrated here for whisking (black) and breathing (red).