From molecule to mind: an integrative perspective on odor intensity

• Olfaction lacks a working model of odor-intensity coding.
• Neural correlates of varying odor concentration lead to simplistic models.
• New models are needed that predict intensity across odors, in mixtures, and after adaptation.

A fundamental problem in systems neuroscience is mapping the physical properties of a stimulus to perceptual characteristics. In vision, wavelength translates into color; in audition, frequency translates into pitch. Although odorant concentration is a key feature of olfactory stimuli, we do not know how concentration is translated into perceived intensity by the olfactory system. A variety of neural responses at several levels of processing have been reported to vary with odorant concentration, suggesting specific coding models. However, it remains unclear which, if any, of these phenomena underlie the perception of odor intensity. Here, we provide an overview of current models at different stages of olfactory processing, and identify promising avenues for future research.