Mice discriminate odour source distance via sub-sniff temporal features of odour plumes

Rodents rely on olfaction to navigate complex environments, particularly where visual cues are limited. Yet how they estimate the distance to an odour source remains unclear. The spatiotemporal dynamics of natural odour plumes, shaped by airflow turbulence, offer valuable cues for locating odour sources. Here, we show that mice can discriminate odour sources placed at different distances by extracting information from the sub-sniff temporal structure of naturalistic odour plumes. Using a wind tunnel and an olfactory virtual reality system, we generated dynamic plumes and demonstrated, through high-throughput automated behaviour, that mice distinguish near from far sources based on odour fluctuations operating faster than their respiratory cycle. Two-photon calcium imaging of olfactory bulb projection neurons revealed that distance-dependent responses are present in a small subset of mitral and tufted cells, and that population activity encodes source distance. Critically, neural responses correlated more strongly with high-frequency plume features than with mean odour concentration. Our results identify a neural basis for distance estimation from odour dynamics and highlight the importance of rapid temporal processing in mammalian olfaction.