Recent odor experience selectively modulates olfactory sensitivity across the glomerular output in the mouse olfactory bulb

Abstract

AbstractAlthough animals can reliably locate and recognize odorants embedded in complex environments, the neural circuits for accomplishing these tasks remain incompletely understood. Adaptation is likely to be important in this process as it could allow neurons in a brain area to adjust to the broader sensory environment. Adaptive processes must be flexible enough to allow the brain to make dynamic adjustments, while also maintaining sufficient stability such that organisms do not forget important olfactory associations. Processing within the mouse olfactory bulb is likely involved in generating adaptation, although there are conflicting models of how it transforms the glomerular output of the mouse olfactory bulb. Here we performed 2-photon Ca2+imaging in awake mice to determine the time course of recovery from adaptation, and whether it acts broadly or selectively acts across the glomerular population. Individual glomerular responses, as well as the overall population odor representation was similar across imaging sessions. However, odor-concentration pairings presented with interstimulus intervals upwards of 30-s could evoke heterogeneous adaptation across the glomerular population. This adaptation was strongest at higher concentrations, unrelated to variations in respiration, and measurements from olfactory receptor neuron glomeruli indicate that it is unlikely to be inherited from the periphery. Our results indicate that the olfactory bulb output reliably transmits stable odor representations, although dynamic processes exist by which recent odor exposure can selectively impact odor sensitivity for upwards of 30 seconds. We propose that dynamic adaptation in subsets of glomeruli is necessary for making dynamic adjustments to complex odor environments.