Dexterous single sniffs for ethological active olfaction.

Abstract

Rhythmic sniffing is considered intrinsic to active olfaction among terrestrial mammals. However, mice are known to briefly hold food under their nares while feeding, suggesting coordination of oromanual dexterity, breathing, and olfaction for nonrhythmic single sniffs. Here, we recorded kinematics and breathing as mice foraged and fed, finding that mice indeed, with clockwork-like dexterity and millisecond timing, synchronize a single inspiration with rapid head and hand movements. These solitary food sniffs are associated with abrupt resetting of the breathing rhythm, differ from stereotypical rhythmic sniffing, and exhibit behavioral modulations for different food properties. Olfactory and motor circuit manipulations demonstrate motor cortical dependence rather than reflexive neural control. Our study extends the concept of active olfaction to include this distinct form of complex motor-sensory coordination, features of which accord with the idea of discrete "snapshot" olfaction.