Our subjective experience of taste is actually a combination of taste and smell. If you sever the olfactory nerve, removing the sense of smell, your ability to taste your food will be much reduced. You will only be able to taste sweet, bitter, salt, and sour flavors. There is now evidence for a fifth type of taste category, however, which has been named umami. This is a Japanese word meaning delicious, savory, or meaty. Umami seems related to monosodium glutamate (MSG), a food additive used extensively in East Asian cuisine.

All of these taste categories have survival value. Sweet, umami, and salty tastes enhance our intake of carbohydrate, protein, and salt, respectively. Excessive amounts of bitter or sour taste alert us to decaying or toxic food. The relative amounts of the taste qualities of any food put in the mouth are sensed by the taste buds (gustatory papillae), tiny protrusions that cover the surface of the tongue. The taste buds are somewhat specialized to specific taste qualities, but generally respond to more than one aspect of taste (e.g., both salty and sweet). The taste buds carry information to the cranial nerves, which connect to neurons in the brain stem, which then connect to neurons in the thalamus. These project (or connect) to a particular area in the somatosensory strip specialized for the tongue.