The Central Pattern Generator for Rhythmic Whisking

Whisking and sniffing are predominant aspects of exploratory behavior in rodents. We review evidence that these motor rhythms are coordinated by the respiratory patterning circuitry in the ventral medulla. A region in the intermediate reticular zone, dorsomedial to the preBötzinger inspiratory complex, provides rhythmic input to the facial motoneurons that drive protraction of the vibrissae. Neuronal output from this region is reset at each inspiration by direct input from the preBötzinger complex. High frequency breathing, or sniffing, has a one-to-one coordination with whisking while basal respiration is accompanied by intervening whisks that occur between breaths. We conjecture that the preBötzinger complex, which projects to neighboring premotor regions for the control of other orofacial muscles, functions as a master clock to coordinate orofacial behaviors with breathing.