INTRODUCTIONObjects can appear remarkably stable despite the often fickle cues they provide to our senses. For instance, a foraging mouse can identify and locate a piece of cheese several meters away entirely by smell, even though the concentration of airborne “cheese” molecules varies steeply over this distance. How the brain maintains perceptual stability across such widely ranging stimulus intensities remains a fundamental, unanswered question. The response properties of olfactory sensory neurons in the mouse’s nose may provide part of the answer. With each sniff, inhaled odorant molecules activate subsets of sensory neurons that each express a single type of odorant receptor. At low concentrations, when only a few odorant molecules are present, only those cells that express the most sensitive receptors for that particular odorant will be activated. However, many cells that express lower-affinity receptors will also be activated at higher concentrations, potentially degrading the odor representation. Crucially, the sensory neurons that express high-affinity receptors will always be activated earliest in the sniff, regardless of concentration. Could the mouse’s brain exploit this temporal structure to maintain stable odor representations despite changing odorant concentrations?
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