Exploratory nose movement: behavioral dynamics and functional brainstem circuits.

Exploration and navigation involves movement of the body and of sensory organs. Positioning of the eyes, ears, whiskers, nose, head and body determine which sensory inputs are collected and attended to. The neural circuitry that controls sensory organ positioning has been studied to reveal the mechanisms by which movement is initiated and gated. Further examples of circuits and quantifications of these behaviors will help to determine general principles of control of movement of sensory organs.In this manuscript I examine movement of the nose, a little-described behavior which is prominent in many rodents. I quantify behavioral features of nose movement, and identify a basic circuit in the brainstem that controls it through a combination of anatomical tracing and functional study. Specifically, I find that nose movement occurs when rodents sniff, is coordinated to breathing, and responds to odor presentation. I identify two putative premotor areas that may control motion of the nose, and show that one of the areas gates nose response to odor presentation. The structure of the nose motion circuit can be compared to circuitry to that of other known orofacial motor actions, such as control of whisker movement and licking. Future work in this system system can help to elucidate common features of orofacial motor control