The olfactory system represents one of the oldest sensory modalities in the phylogenetic history of mammals. (See the image below.) As a chemical sensor, the olfactory system detects food and influences social and sexual behavior. The specialized olfactory epithelial cells characterize the only group of neurons capable of regeneration. Within the nasal cavity, the turbinates or nasal conchae serve to direct the inspired air toward the olfactory epithelium in the upper posterior region. This area (only a few centimeters wide) contains more than 100 million olfactory receptor cells.