Efficient sensory codes convey new information while reducing redundancy. Adaptation helps to build efficient codes by allowing neurons and networks to minimize their responses to background stimuli, and conversely to boost signals from stimuli that are unexpected and therefore informative. Thus, by instantiating the prediction that the world now will be similar to the world a moment ago, adaptation enables sensory systems to filter the past and to selectively convey information about novel cues in the future. While mechanisms supporting rapid (e.g., milliseconds to seconds) adaptation have been well characterized in the olfactory system — and reformat fast, dynamic stimuli such as odor plumes — it is not clear whether or how olfactory neurons adapt at the longer timescales at which animals traverse different natural odor environments. Here we describe a novel mechanism for sensory adaptation that enables different odor environments to imprint themselves upon the olfactory system. This mechanism enables the olfactory system to instantiate expectation, thereby building odor codes that are personalized by each animal’s specific and ongoing odor experience.