Summary

The gustatory system has evolved to detect molecules dissolved into the saliva. It is responsible for the perception of taste and flavor, for mediating the interaction between perception and internal homoeostatic states, and for driving ingestive decisions. The widely recognized five basic taste categories (sweet, salty, bitter, sour, and umami) provide information about the nutritional or potentially harmful content in what is being consumed. Sweetness is typical of sugars that are carbohydrate dense; saltiness is the percept of ions which are necessary for physiological function and electrolytic homeostasis; bitterness is associated with alkaloids and other potential toxins; sourness is the percept of acidity signaling spoiling foods; and umami is the sensation associated with amino acids in protein-rich foods. In addition to taste, the act of eating also engages sensations of temperature, texture, and odor—the integration of all these sensations leads to the unitary percept of flavor. These same senses, and others such as vision and audition, are also engaged before an ingestive event. Sights, sounds, and smells can alert organisms to the presence of food as well as inform the organism as to the specifics of which taste(s) to expect. As such, the neurophysiology of taste is necessarily intertwined with that of other senses and with that of cognitive and homeostatic systems.