Abstract

Dynamical changes in the environment strongly impact our perception 1,2. Consistent with this, sensory systems preferentially represent stimulus changes, enhancing temporal contrast 3,4. In olfaction, odor concentration changes across consecutive inhalations ({Delta}Ct) can guide odor source localization. Yet the neural representation of {Delta}Ct has not been studied in vertebrates. We have found that a subset of mitral/tufted (M/T) cells in the olfactory bulb explicitly represent {Delta}Ct. These concentration change detectors are direction selective: some respond to positive {Delta}Ct, while others represent negative {Delta}Ct. This change detection enhances the contrast between different concentrations and the magnitude of contrast enhancement scales with the size of the concentration step. Further, {Delta}Ct can be read out from the total spike count per sniff, unlike odor identity and intensity, which are represented by fast temporal spike patterns. Our results demonstrate that a subset of M/T cells explicitly represents {Delta}Ct, providing a signal that may instruct navigational decisions in downstream olfactory circuits.