Taste

Related Topics:
Tasteless :: Taste_of_Cherry,_The :: Taste_of_Others,_The

Taste is one of the most common and fundamental of the senses of animals. It is the direct detection of chemical composition, usually through contact with chemoreceptor cells. Taste is very similar to olfaction, the sense of smell, in which the chemical composition of an organism's ambient medium is detected by chemoreceptors. It helps determine flavor.

Role of the nervous system

In humans, the sense of taste is transduced by taste buds and is conveyed via three of the twelve cranial nerves. The facial nerve carries taste sensations from the anterior two thirds of the tongue (excluding the circumvallate papillae, see lingual papilla) and soft palate, the glossopharyngeal nerve carries taste sensations from the posterior one third of the tongue (including the circumvallate papillae) while a branch of the vagus nerve carries some taste sensations from the back of the oral cavity (i.e. pharynx and epiglottis). Information from these cranial nerves is processed by the gustatory system.

It is important to note that the axons from these cranial nerves ascend in the spinal cord without crossing over. These fibers terminate in the amygdala, hypothalamus, and ventral posterior medial nucleus of the thalamus, which then projects to the somatosensory cortex within the brain. Thus, a lesion of the rostral nucleus solitarius, tractus solitarius, or solitariothalamic tract results in loss of taste from the ipsilesional, the same side as the lesion, half of the tongue.

Basic classification of tastes

As a general rule, taste is a holistic assessment of the interaction of the fundamental taste systems of sweetness, sourness, bitterness, saltiness, and umami, or "savouriness". Location of the stimulus on the tongue is not important, despite the common misperception of a "taste map" of sensitivity to different tastes thought to correspond to specific areas of the tongue ^*. 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. In reality, the separate populations of taste buds, sensing each of the basic tastes, are distributed across the tongue, though not entirely equally; for instance, the front of the mouth is biased toward sweetness and the rear toward bitterness. The brain also plays a part in the tounge's sensory distribution. If, for instance, half of the tongue is blocked from sending information to the brain, rather than any diminishment, people will instead report that a doubling of psychological perception has occurred for each taste, and no loss to any one.

New evidence is emerging that supports the inclusion of a sixth taste category for free fatty acids, the chemical components of dietary fat. A taste receptor mechanism for free fatty acids has been identified an animal model for the detection of free fatty acids is being characterized ^*.

Factors affecting taste perception

Many factors affect taste perception, including:

Aging
Hormonal influences
Genetic variations - See Phenylthiocarbamide
Oral temperature
Drugs and chemicals

It is also important to consider that flavour is the overall, total sensation induced during mastication (e.g. taste, touch, pain and smell). Smell (olfactory stimulation) plays a major role in flavour perception.

Disorders of taste

ageusia (complete loss)
hypogeusia (partial loss)
parageusia (unpleasant taste)
dysgeusia (inaccurate taste)

Taste in aesthetics

Main article taste (aesthetics).

Taste can also refer to appreciation for aesthetic quality, significantly applying the purely physical term to an intellectual quality. In such contexts Taste begins to be used in a metaphorical sense to refer to certain degrees of cultural competence, closely related to the concept of discrimination; it can set distinctions between "tasteful" and "tasteless" or the embodiments of "good taste" or "bad taste", thus providing categories for social division and reinforcing cultural hierarchy.

The modern concept of "taste" is a product of the 16th century Italian Mannerism: the idea of "taste" as a quality that is independent of the style that is simply its vehicle — though the style might be designated a taste, such as "the Antique taste"— was born in the circle of Pope Julius III and first realized at the Villa Giulia he built on the edge of Rome in 1551–1555.

To the Enlightenment, "taste" was still a universal character, which could be recognized by what pleased any cultured sensibility. With the shift in perspective that Romanticism brought, it began to be thought that, to the contrary, "Beauty is in the eye of the beholder" and could be individually interpreted, with results that might be of equivalent aesthetic value.

Taste as a metaphor'' for experience or knowledge

To taste is also used metaphorically to describe having a small amount of experience with something that gives a sense of its quality as a whole. Livy is quoted to have said "they had not yet tasted the sweetness of freedom" while Voltaire is quoted to have said "I tasted in her arms the delights of paradise". The word is often used as a noun in this sense, typically in such expressions as "I got a taste of it" or "It left a bad taste in my mouth."