palatability

The palatability of a substance is determined by opioid receptor-related processes in the nucleus accumbens and ventral pallidum.{{Cite journal |last1=Wassum |first1=K. M. |last2=Ostlund |first2=S. B. |last3=Maidment |first3=N. T. |last4=Balleine |first4=B. W. |date=2009-07-28 |title=Distinct opioid circuits determine the palatability and the desirability of rewarding events |journal=Proceedings of the National Academy of Sciences |language=en |volume=106 |issue=30 |pages=12512–12517 |doi=10.1073/pnas.0905874106 |issn=0027-8424 |pmc=2718390 |pmid=19597155 |bibcode=2009PNAS..10612512W |doi-access=free }} The opioid processes involve mu opioid receptors and are present in the rostromedial shell part of the nucleus accumbens{{Cite journal |last1=Peciña |first1=Susana |last2=Berridge |first2=Kent C. |date=2005-12-14 |title=Hedonic Hot Spot in Nucleus Accumbens Shell: Where Do μ-Opioids Cause Increased Hedonic Impact of Sweetness? |journal=The Journal of Neuroscience |language=en |volume=25 |issue=50 |pages=11777–11786 |doi=10.1523/JNEUROSCI.2329-05.2005 |issn=0270-6474 |pmc=6726018 |pmid=16354936}} on its spiny neurons.{{Cite journal |last1=Kelley |first1=A. E. |last2=Bakshi |first2=V. P. |last3=Haber |first3=S. N. |last4=Steininger |first4=T. L. |last5=Will |first5=M. J. |last6=Zhang |first6=M. |date=2002-07-01 |title=Opioid modulation of taste hedonics within the ventral striatum |journal=Physiology & Behavior |volume=76 |issue=3 |pages=365–377 |doi=10.1016/s0031-9384(02)00751-5 |issn=0031-9384 |pmid=12117573|s2cid=44258056 }} This area has been called the "opioid eating site".{{Cite journal |last1=Peciña |first1=Susana |last2=Berridge |first2=Kent C. |date=2000-04-28 |title=Opioid site in nucleus accumbens shell mediates eating and hedonic 'liking' for food: Map based on microinjection Fos plumes |journal=Brain Research |volume=863 |issue=1–2 |pages=71–86 |doi=10.1016/s0006-8993(00)02102-8 |issn=0006-8993 |pmid=10773195|s2cid=1805234 }}

The rewardfulness of consumption associated with palatability is dissociable from desire or incentive value which is the motivation to seek out a specific commodity. Desire or incentive value is processed by opioid receptor-related processes in the basolateral amygdala. 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.{{Cite journal |last1=Finlayson |first1=Graham |last2=King |first2=Neil |last3=Blundell |first3=John |date=2008-01-01 |title=The role of implicit wanting in relation to explicit liking and wanting for food: implications for appetite control |journal=Appetite |volume=50 |issue=1 |pages=120–127 |doi=10.1016/j.appet.2007.06.007 |issn=0195-6663 |pmid=17655972|s2cid=54347866 |url=http://eprints.whiterose.ac.uk/96699/2/finlayson%20et%20al%202008%20appetite%20manuscript.pdf }}

Though the wanting of incentive salience may be informed by palatability, it is independent and not necessarily reduced to it. 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.

It has also been suggested that hedonic hunger can be driven both in regard to "wanting" and "liking" and that a palatability subtype of neuron may also exist in the basolateral amygdala.{{Cite journal |last1=Fontanini |first1=Alfredo |last2=Grossman |first2=Stephen E. |last3=Figueroa |first3=Joshua A. |last4=Katz |first4=Donald B. |date=2009-02-25 |title=Distinct subtypes of basolateral amygdala taste neurons reflect palatability and reward |journal=The Journal of Neuroscience |volume=29 |issue=8 |pages=2486–2495 |doi=10.1523/JNEUROSCI.3898-08.2009 |issn=1529-2401 |pmc=2668607 |pmid=19244523}}

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.{{Cite journal |last=Smith |first=Gerard P. |date=2000-10-01 |title=The controls of eating: a shift from nutritional homeostasis to behavioral neuroscience |journal=Nutrition |volume=16 |issue=10 |pages=814–820 |doi=10.1016/s0899-9007(00)00457-3 |issn=0899-9007 |pmid=11054585}} 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.{{Cite journal |last=Smith |first=Gerard P. |date=1996-01-01 |title=The direct and indirect controls of meal size |journal=Neuroscience and Biobehavioral Reviews |volume=20 |issue=1 |pages=41–46 |doi=10.1016/0149-7634(95)00038-g |issn=0149-7634 |pmid=8622828|s2cid=8313724 |doi-access=free }} The influence of these processes can exist without subjective awareness.{{Cite journal |last=Berridge |first=Kent C. |date=1996-01-01 |title=Food reward: Brain substrates of wanting and liking |journal=Neuroscience and Biobehavioral Reviews |volume=20 |issue=1 |pages=1–25 |doi=10.1016/0149-7634(95)00033-b |issn=0149-7634 |pmid=8622814 |s2cid=18707849}}

The cessation of a desire to eat after a meal "satiation" is likely to be due to different processes and cues.{{Citation |last1=Dalton |first1=M. |title=Hedonics, satiation and satiety |date=2013-01-01 |work=Satiation, Satiety and the Control of Food Intake |pages=221–237 |editor-last=Blundell |editor-first=John E. |series=Woodhead Publishing Series in Food Science, Technology and Nutrition |publisher=Woodhead Publishing |doi=10.1533/9780857098719.4.221 |isbn=978-0-85709-543-5 |last2=Finlayson |first2=G. |editor2-last=Bellisle |editor2-first=France}} More palatable foods reduce the effects of such cues upon satiation causing a larger food intake, exploited in hyperpalatable food.{{Cite journal |last1=Yeomans |first1=M. R. |last2=Lee |first2=M. D. |last3=Gray |first3=R. W. |last4=French |first4=S. J. |date=2001-08-01 |title=Effects of test-meal palatability on compensatory eating following disguised fat and carbohydrate preloads |journal=International Journal of Obesity and Related Metabolic Disorders |volume=25 |issue=8 |pages=1215–1224 |doi=10.1038/sj.ijo.0801653 |pmid=11477507|s2cid=37835293 }}{{Cite journal |last1=Robinson |first1=Tristan M. |last2=Gray |first2=Richard W. |last3=Yeomans |first3=Martin R. |last4=French |first4=Stephen J. |date=2005-02-15 |title=Test-meal palatability alters the effects of intragastric fat but not carbohydrate preloads on intake and rated appetite in healthy volunteers |journal=Physiology & Behavior |volume=84 |issue=2 |pages=193–203 |doi=10.1016/j.physbeh.2004.11.004 |issn=0031-9384 |pmid=15708771|s2cid=33711162 }} 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.{{Cite journal |last=Bowers |first=M. Deane |date=1981 |title=Unpalatability as a Defense Strategy of Western Checkerspot Butterflies (Euphydryas scudder, Nymphalidae) |jstor=2407845 |journal=Evolution |volume=35 |issue=2 |pages=367–375 |doi=10.2307/2407845 |pmid=28563381 |issn=0014-3820}}

• Acquired taste
• Flavor
• Food craving
• Motivation
• Nutrition
• Pleasure center

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Category:Behavioral neuroscience

Category:Gustation

Category:Gustatory system