  The olfactory sense measures the chemical composition of the environment
using a diverse array of olfactory receptors. In vertebrates, the olfactory
receptors reside in a mucus layer in the nasal cavity and can thus only detect
odorants that are inhaled with the airflow and dissolved in mucus. These
physical processes fundamentally affect how many odorant molecules contact the
receptors. We hypothesize that the olfactory system works efficiently by
optimizing the placement of receptors for maximal information transmission.
Using a simplified model, we capture all relevant physical processes and show
that odorant concentrations generally exhibit an exponential distribution.
Combining this result with information theory, we further show that receptors
separated into distinct spatial zones maximize the transmitted information. Our
results are consistent with experimentally observed receptors zones and might
help to improve artificial smell sensors.
