The spiking output of the mouse olfactory bulb encodes large-scale temporal features of natural odor environments

Abstract

Spatiotemporal dynamics of natural odor environment have informative features for animals navigating to an odor source. Population activity in the olfactory bulb (OB) has been shown to follow plume dynamics to a moderate degree (Lewis et al., 2021), but it is unknown whether the ability to follow plume dynamics is driven by individual cells or whether it emerges at the population level. Previous research has explored the responses of individual OB cells to isolated features of plumes, but it is difficult to adequately sample these features as it is still undetermined which features navigating mice employ during olfactory guided search. Here we released odor from an upwind odor source and simultaneously recorded both odor concentration dynamics and cellular response dynamics in awake, head-fixed mice. We found that longer timescale features of odor concentration dynamics were encoded at both the cellular and population level. At the cellular level, plume onset was encoded across all trials and plume offset was encoded for high concentration odors, but not low concentration odors. Although cellular level tracking of plume dynamics was observed to be weak, we found that at the population level, OB activity distinguished whiffs and blanks (accurately detected odor presence versus absence) throughout the duration of a plume. Even ~20 OB cells were enough to accurately encode these features. Our findings indicate that the full range of odor concentration dynamics and high frequency fluctuations are not encoded by OB spiking activity. Instead, relatively lower-frequency dynamics of plumes, such as plume onset, plume offset, whiffs, and blanks, are represented in the OB.