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Palatability

Advertisement of castor oil as a medicine by Scott & Bowne company, 19th century

Palatability (or palatableness) is the hedonic reward (which is pleasure of taste in this case) provided by foods or drinks that are agreeable to the "palate", which often varies relative to the homeostatic satisfaction of nutritional and/or water needs.[1] The palatability of a dish or beverage, unlike its flavor or taste, varies with the state of an individual: it is lower after consumption and higher when deprived. It has increasingly been appreciated that this can create a hunger that is independent of homeostatic needs.[2]

Brain mechanism

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The palatability of a substance is determined by opioid receptor-related processes in the nucleus accumbens and ventral pallidum.[3] The opioid processes involve mu opioid receptors and are present in the rostromedial shell part of the nucleus accumbens[4] on its spiny neurons.[5] This area has been called the "opioid eating site".[6]

The rewardfulness of consumption associated with palatability is dissociable from desire or incentive value which is the motivation to seek out a specific commodity.[3] Desire or incentive value is processed by opioid receptor-related processes in the basolateral amygdala.[3] Unlike the liking palatability for food, the incentive salience wanting is not downregulated by the physiological consequences of food consumption and may be largely independent of homoeostatic processes influencing food intake.[7]

Though the wanting of incentive salience may be informed by palatability, it is independent and not necessarily reduced to it.[3] It has been suggested that a third system exists that links opioid processes in the two parts of the brain: "Logically this raises the possibility that a third system, with which the accumbens shell, ventral pallidum, and basolateral amygdala are associated, distributes the affective signals elicited by specific commodities across distinct functional systems to control reward seeking... At present we do not have any direct evidence for a system of this kind, but indirect evidence suggests it may reside within the motivationally rich circuits linking hypothalamic and brainstem viscerogenic structures such as the parabrachial nucleus.[3]

It has also been suggested that hedonic hunger can be driven both in regard to "wanting" and "liking"[2] and that a palatability subtype of neuron may also exist in the basolateral amygdala.[8]

Satiety and palatability

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Appetite is controlled by a direct loop and an indirect one. In both the direct and indirect loops there are two feedback mechanisms. First a positive feedback involving its stimulation by palatability food cues, and second, a negative feedback due to satiation and satiety cues following ingestion.[9] In the indirect loop these cues are learnt by association such as meal plate size and work by modulating the potency of the cues of the direct loop.[10] The influence of these processes can exist without subjective awareness.[11]

The cessation of a desire to eat after a meal "satiation" is likely to be due to different processes and cues.[12] More palatable foods reduce the effects of such cues upon satiation causing a larger food intake, exploited in hyperpalatable food.[13][14] In contrast, unpalatability of certain foods can serve as a deterrent from feeding on those foods in the future. For example, the variable checkerspot butterfly contains iridoid compounds that are unpalatable to avian predators, thus reducing the risk of predation.[15]

See also

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References

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  1. ^ Friedman, Mark I.; Stricker, Edward M. (1976). "The physiological psychology of hunger: A physiological perspective". Psychological Review. 83 (6): 409–431. doi:10.1037/0033-295X.83.6.409. ISSN 1939-1471. PMID 1005583.
  2. ^ a b Lowe, Michael R.; Butryn, Meghan L. (2007-07-24). "Hedonic hunger: A new dimension of appetite?". Physiology & Behavior. 91 (4): 432–439. doi:10.1016/j.physbeh.2007.04.006. ISSN 0031-9384. PMID 17531274. S2CID 10704679.
  3. ^ a b c d e Wassum, K. M.; Ostlund, S. B.; Maidment, N. T.; Balleine, B. W. (2009-07-28). "Distinct opioid circuits determine the palatability and the desirability of rewarding events". Proceedings of the National Academy of Sciences. 106 (30): 12512–12517. Bibcode:2009PNAS..10612512W. doi:10.1073/pnas.0905874106. ISSN 0027-8424. PMC 2718390. PMID 19597155.
  4. ^ Peciña, Susana; Berridge, Kent C. (2005-12-14). "Hedonic Hot Spot in Nucleus Accumbens Shell: Where Do μ-Opioids Cause Increased Hedonic Impact of Sweetness?". The Journal of Neuroscience. 25 (50): 11777–11786. doi:10.1523/JNEUROSCI.2329-05.2005. ISSN 0270-6474. PMC 6726018. PMID 16354936.
  5. ^ Kelley, A. E.; Bakshi, V. P.; Haber, S. N.; Steininger, T. L.; Will, M. J.; Zhang, M. (2002-07-01). "Opioid modulation of taste hedonics within the ventral striatum". Physiology & Behavior. 76 (3): 365–377. doi:10.1016/s0031-9384(02)00751-5. ISSN 0031-9384. PMID 12117573. S2CID 44258056.
  6. ^ Peciña, Susana; Berridge, Kent C. (2000-04-28). "Opioid site in nucleus accumbens shell mediates eating and hedonic 'liking' for food: Map based on microinjection Fos plumes". Brain Research. 863 (1–2): 71–86. doi:10.1016/s0006-8993(00)02102-8. ISSN 0006-8993. PMID 10773195. S2CID 1805234.
  7. ^ Finlayson, Graham; King, Neil; Blundell, John (2008-01-01). "The role of implicit wanting in relation to explicit liking and wanting for food: implications for appetite control" (PDF). Appetite. 50 (1): 120–127. doi:10.1016/j.appet.2007.06.007. ISSN 0195-6663. PMID 17655972. S2CID 54347866.
  8. ^ Fontanini, Alfredo; Grossman, Stephen E.; Figueroa, Joshua A.; Katz, Donald B. (2009-02-25). "Distinct subtypes of basolateral amygdala taste neurons reflect palatability and reward". The Journal of Neuroscience. 29 (8): 2486–2495. doi:10.1523/JNEUROSCI.3898-08.2009. ISSN 1529-2401. PMC 2668607. PMID 19244523.
  9. ^ Smith, Gerard P. (2000-10-01). "The controls of eating: a shift from nutritional homeostasis to behavioral neuroscience". Nutrition. 16 (10): 814–820. doi:10.1016/s0899-9007(00)00457-3. ISSN 0899-9007. PMID 11054585.
  10. ^ Smith, Gerard P. (1996-01-01). "The direct and indirect controls of meal size". Neuroscience and Biobehavioral Reviews. 20 (1): 41–46. doi:10.1016/0149-7634(95)00038-g. ISSN 0149-7634. PMID 8622828. S2CID 8313724.
  11. ^ Berridge, Kent C. (1996-01-01). "Food reward: Brain substrates of wanting and liking". Neuroscience and Biobehavioral Reviews. 20 (1): 1–25. doi:10.1016/0149-7634(95)00033-b. ISSN 0149-7634. PMID 8622814. S2CID 18707849.
  12. ^ Dalton, M.; Finlayson, G. (2013-01-01), Blundell, John E.; Bellisle, France (eds.), "Hedonics, satiation and satiety", Satiation, Satiety and the Control of Food Intake, Woodhead Publishing Series in Food Science, Technology and Nutrition, Woodhead Publishing, pp. 221–237, doi:10.1533/9780857098719.4.221, ISBN 978-0-85709-543-5
  13. ^ Yeomans, M. R.; Lee, M. D.; Gray, R. W.; French, S. J. (2001-08-01). "Effects of test-meal palatability on compensatory eating following disguised fat and carbohydrate preloads". International Journal of Obesity and Related Metabolic Disorders. 25 (8): 1215–1224. doi:10.1038/sj.ijo.0801653. PMID 11477507. S2CID 37835293.
  14. ^ Robinson, Tristan M.; Gray, Richard W.; Yeomans, Martin R.; French, Stephen J. (2005-02-15). "Test-meal palatability alters the effects of intragastric fat but not carbohydrate preloads on intake and rated appetite in healthy volunteers". Physiology & Behavior. 84 (2): 193–203. doi:10.1016/j.physbeh.2004.11.004. ISSN 0031-9384. PMID 15708771. S2CID 33711162.
  15. ^ Bowers, M. Deane (1981). "Unpalatability as a Defense Strategy of Western Checkerspot Butterflies (Euphydryas scudder, Nymphalidae)". Evolution. 35 (2): 367–375. doi:10.2307/2407845. ISSN 0014-3820. JSTOR 2407845. PMID 28563381.