Rapid temporal processing in the olfactory bulb underlies concentration invariant odor identification and signal decorrelation.

Abstract

In a dynamic environment, sensory systems must filter out irrelevant information to construct a stable percept. Animals who rely on smell need to identify and discriminate odors despite fluctuations in concentration, yet odor receptor activation is strongly concentration-dependent. Here, we explored how odor signals are transformed within the mouse olfactory bulb (OB) by developing an all-optical approach to identify the connectivity between odor receptor channels (glomeruli) and the mitral and tufted cells (MTCs), while monitoring their odor responses. We found that the glomeruli and MTCs activated earliest in a sniff robustly represented odor identity across concentrations, while MTCs connected to later-activated glomeruli were concentration-dependent. Furthermore, probing the responsiveness of MTCs to glomerular input found a short temporal window of excitability at a sniff's start, followed by prolonged odor-evoked inhibition. Our findings reveal a temporal filter implemented by the OB, responsible for stabilizing identity across concentrations while decorrelating responses between odors.