How the body rules the nose

In order to survive, an organism has to adapt its behavioral actions to the current context by carefully balancing sensory input with physiological state and need. This challenge becomes particularly apparent for olfactory stimuli (volatile chemicals), which can signal not only food sources, mating partners, and offspring, but also pathogens, competitors, and predators. To achieve this difficult task, information processing in the olfactory system is strongly modulated by internal state (for example, metabolic or endocrine), environmental context, and previous experience. This article provides an overview how different internal states impact olfactory processing and discusses potential underlying mechanisms. It starts with a brief excurse on a leading model to study olfaction—Mus musculus—and concludes with implications for human health and disease.