Functional magnetic resonance imaging of human olfaction

A hierarchical organization of the olfactory system has been elucidated, mainly in animal studies. From the olfactory receptors and olfactory bulb, olfactory information is projected to the primary olfactory cortex, which is located at the posterior part of the orbital cortex and the medial aspect of the temporal lobe. Various secondary regions have been shown to receive projections from the primary olfactory cortex; however, human lesion studies and neuroimaging experiments have only begun to elucidate how the human brain encodes the quality of odors, odor-associated memories, and emotions. Further fMRI studies of olfaction will focus on these issues and promise to advance our understanding of odor perception in humans.