How does perception of odors work?

Perception of odors begins with the inhalation, which allows volatile chemicals to enter the nose. These are initially trapped by a mucosal lining in the nose. Above this lining, approximately two centimeters above the roof of the mouth, is the olfactory bulb. This structure contains neurons that project into the mucosal lining and respond to different odorant compounds.

These olfactory neurons then transmit signals deeper into the brain along different pathways. One pathway involves innate responses to odors, which include hard-wired reactions to things like smoke, signaling potential danger. These signals are sent to the amygdala, which is associated with threat detection and fear response. Another pathway is responsible for appetitive behaviors, causing us to approach pleasant smells like food, which requires no prior learning.

Additionally, some odor response pathways are involved in learned associations, allowing us to form memories and contextual responses to various smells over time 1.