Final Report Summary - ACTIVE SNIFFING (The Algorithmic and Neuronal Basis of Active Sensing in the Case of Odor-Trail Tracking)
Sensory perception is an active process. For instance, during normal vision an animal makes quick movements of the eye and fixates its gaze to a specific region of a visual scene. The visual system actively determines what parts of the visual environment it is going to sample. This common behavior, called active sensing, is not unique to the visual system, in fact many sensory systems operate in such a fashion and olfaction, the sense of smell, is no exception. Olfaction in rodents is an important model for active sensing. Rodents excel at the sense of smell, which is critical for finding mates and food, as well as for avoiding predators and toxins. Rodents smell by tracking either air-borne odors or surface-borne trails on the ground. During tracking, the animal decides when and where to sample space thereby updating an internal representation of its environment that ultimately guides its behavior. This sampling is achieved by ’sniffing’, which is defined as voluntary inhalation, and can happen at frequencies of up to four times the baseline respiration rate. This project investigated active sensing in the context of olfactory trail tracking in mice and its neuronal basis. To effectively tackle this question, we developed a novel high-throughput experimental system that allows the delivery of odor trails to a belt in real-time by using inkjet-printing technology. Subsequently we demonstrated that after a short habituation phase, mice will track the printed odor trails, if one also delivers rewards to the trail at random intervals. We have also established deep learning methods to accurately reconstruct the movements of the snout in 3D space during trail tracking from videography, which together with wireless sniff recordings allowed us to accurately measure where and when mice sampled the odor trail without obstructing the natural movement of mice. Ongoing efforts remain dedicated to analyze mouse behavior during trail tracking towards characterizing their trail tracking behavior.