Taste: Central Processing

Abstract

The taste system monitors the chemical environment to detect carbohydrates, proteins, fats and salt to be consumed and toxins to be avoided. It activates reflexes for swallowing or rejection, and powerful hedonic mechanisms of pleasure or disgust. Electrophysiological and neural imaging studies are revealing taste's neural organisation. The weight of evidence implies that reflexive responses to tastants are orchestrated in the hindbrain, that a cognitive analysis of taste quality and intensity is completed in primary taste cortex, and that the reward value of a taste is added in secondary taste cortex and in ventral forebrain areas. Taste signals are also integrated with those from touch, smell, vision and the viscera to compose a sense of flavour.

Key Concepts:

  • The taste system protects us from ingesting toxins through rejection reflexes and a sense of disgust; it encourages us to consume nutrients through swallowing reflexes and a sense of pleasure.

  • A cognitive identification of taste is most likely made in primary taste cortex in the insula.

  • Taste information is integrated with that from other senses in cortical and ventral forebrain areas to create a sense of flavour.

  • Taste and flavour are imbued with hedonic tone – pleasure or disgust – in orbitofrontal cortex and ventral forebrain.

Keywords: taste; nucleus of the solitary tract; thalamic taste area; insula; orbitofrontal cortex; amygdala; hypothalamus; functional MRI; PET scan; electrophysiology; hedonics

Figure 1.

Transverse sections summarising the afferent limb of the central gustatory projections in the cynomolgus macaque. Abbreviations: AC, anterior commissure; Acc, nucleus accumbens; Am, amygdala; Ca, caudate; CI, claustrum; CP, cerebellar peduncle; GP, globus pallidus; Hyp, hypothalmus; I, insula; IO, inferior olive; Lf, lateral fissure; LGN, lateral geniculate nucleus; NC, nucleus cuneatus; NTS, nucleus of the solitary tract; O, operculum; OC, optic chiasm; OFC, orbitofrontal cortex; OT, optic tract; Put, putamen; SN, substantia nigra; T, thalamus; TL, temporal lobe; V, Ventricle; VPMpc, ventroposterior medial nucleus of the thalamus, pars parvicellularis. Reproduced from Scott TR and Giza BK (1994) Viscerosensory integration and sensory coding in the NTS. In: Borraco RA (ed.) Nucleus of the Solitary Tract, pp. 349–359. Boca Raton: CRC Press.

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Further Reading

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Lemon CH and Katz DB (2007) The neural processing of taste. BMC Neuroscience 8: S5.

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Pritchard TC (2012) Gustatory System. In: Mai JK and Paxino G (eds) The Human Nervous System, 3rd edn, pp. 1187–1218. London: Academic Press.

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Scott, Thomas R(Nov 2012) Taste: Central Processing. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0020288.pub2]