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Taste is one of the traditional five senses and refers to the ability to detect the flavor of foodstuffs and other substances (e.g. poisons). In humans and many other vertebrate animals the sense of taste partners with the sense of smell, in the brain's perception of flavor. Classical taste sensations include sweet, salty, sour, and bitter. More recently, psychophysicists and neuroscientists have suggested other taste categories (umami and fatty acid taste most prominently.)
Taste is a sensory function of the central nervous system. The receptor cells for taste in humans are found on the surface of the tongue, along the soft palate, and in the epithelium of the pharynx and epiglottis.
In humans, taste stimuli are transduced by taste receptor cells which are most commonly found in clusters called taste buds. Taste cells excite sensory afferents found in three of the twelve cranial nerves. The facial nerve relays information from the anterior two thirds of the tongue and soft palate, the glossopharyngeal nerve from the posterior one third of the tongue, and the vagus nerve from the pharynx and epiglottis. Information from these cranial nerves is processed centrally first in the nucleus of the solitary tract of the medulla oblongata and then by a variety of forebrain and cortical structures.
Psychophysicists have long suggested the existence of four taste 'primaries', referred to as the basic tastes: sweetness, sourness, bitterness, and saltiness. Umami, or savoriness, has been suggested as a fifth basic taste, exemplified by the non-salty sensations evoked by MSG (monosodium glutamate). Other possible categories have been suggested, such as a taste exemplified by certain fatty acids such as linoleic acid (see [1], [2], [3]). Some researchers still argue against the notion of primaries at all and instead favor a continuum of percepts, in sharp contrast to color vision.
All of these taste sensations arise from all regions of the oral cavity, despite the common misperception of a "taste map" of sensitivity to different tastes thought to correspond to specific areas of the tongue [4]. The "mouth map" is a myth, generally attributed to the mis-translation of a German text, and perpetuated in North American schools since the early twentieth century [1]. Very slight regional differences in sensitivity to compounds exist, though these regional differences are subtle and do not conform exactly to the mythical tongue map. Individual taste buds (which contain approximately 100 taste receptor cells), in fact, typically respond to compounds evoking each of the four basic tastes.
Many factors affect taste perception, including: