Chapter 7: Odors and Taste

Olfactory receptor neurons in the nasal epithelium bind odorant molecules and transmit signals through the olfactory nerve to the olfactory bulb, which performs initial processing before relaying information to higher brain regions including the pyriform cortex, amygdala, and hippocampus. This direct connection to emotion and memory centers explains why smells can trigger vivid emotional responses and autobiographical memories more powerfully than other sensory modalities. The gustatory system operates through taste receptor cells on the tongue that respond to five basic taste qualities—sweet, salty, sour, bitter, and umami—each signaling different nutritional or potentially harmful properties of foods. Taste signals travel from the tongue via cranial nerves to the brainstem, then through the thalamus to the primary gustatory cortex in the insula, where taste perception becomes conscious. Flavor perception emerges from the integration of taste, smell, and trigeminal sensation, which explains why olfactory dysfunction from illness or nasal congestion dramatically reduces food palatability. The chapter discusses how the orbitofrontal cortex integrates chemical sensory information with reward and satiety signals to modulate food consumption and pleasure. Additionally, the chapter addresses chemosensory disorders such as anosmia and ageusia, examining their causes including viral infection, head trauma, and aging. The potential role of pheromones in human behavior receives examination, though evidence for their influence remains more ambiguous in humans than in other mammals. Finally, the chapter explores how satiety and postingestive feedback modify taste responsiveness, demonstrating that sensory perception of food depends not only on physical stimulus properties but also on metabolic and motivational states.