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Chemosensory Disorders and Nutrition
Published in Alan R. Hirsch, Nutrition and Sensation, 2023
Carl M. Wahlstrom, Alan R. Hirsch, Bradley W. Whitman
Nutrition regulates the chemosenses, and reciprocally, taste and smell greatly influence food selection, satiety, digestion, dietary patterns, and nutrient intake. While the name “gustation” suggests the link between the sense of taste and food, the sense of olfaction is linked in a variety of complex ways. The quintessential position of smell in the chemosensory hierarchy is epitomized by human’s ability to discriminate over one trillion unique olfactory stimuli as opposed to only four or five different tastes (Keller, Dushdid, Magnasco, and Vosshall 2014). Approximately ninety percent of “taste” or flavor is actually smell (Hirsch 1992a). It is a nonpathological form of synesthesia, wherein orthonasal smell is perceived as aroma and retronasal smell, from the posterior of the mouth through the oropharynx, is construed as taste (Bingham, Birch, deGraaf, Behan, and Perring 1990; Murphy and Cain 1980) (see Chapter 3). Olfaction begins exerting its effects when stimuli are remote and its potential roles in nutritional assessments are areas of ongoing research (Griep et al. 1999). Attributes of nutritional metabolism and physiology are both enmeshed in this nexus and serve as a powerful milieu regulating disparate chemosensory forces which powerfully come together and impact one another, to yield relevant changes in the human sensory response, behavioral outcomes, and ultimately resulting in impact upon human health.
Role of the Cortical Gustatory Area in Taste Discrimination
Published in Robert H. Cagan, Neural Mechanisms in Taste, 2020
Benjamin and Pfaffmann18 and Benjamin and Akert50 showed a slight increase (less than 10 times higher than normal) in the threshold for quinine aversion after lesions of the rat CGA. However, later research demonstrated that bilateral ablations of the CGA induced no deficit in gustation or had essentially no effects on simple preference-aversion behavior,21,51–54 although Braun et al.21,51 reported an enhanced ingestion of moderate and high concentrations of NaCl and sucrose solutions after cortical lesions. Grill and Norgren4 showed that taste reactivity based on hedonic aspects of taste stimuli (acceptable vs. rejective) was primarily integrated at the brain stem level without involving higher central activities.
ENTRIES A–Z
Published in Philip Winn, Dictionary of Biological Psychology, 2003
The sense of taste. Gustation is chemically mediated, receptors on the tongue detecting each of four prototypical tastes: sweet, sour, bitter and salt. (MONOSODIUM GLUTAMATE, used to enhance flavour, may be a primary taste called UMAMI.) Taste perception begins at TASTE BUDS on the tongue. Taste buds are responsive to specific primary tastes and are differently distributed across the tongue. The tip of the tongue is most sensitive to sweet and salt, the sides to sour, and the back to bitter. Individual taste buds possess 20-50 RECEPTOR cells clustered together and, in order to be tasted, a molecule must be water-soluble and able to bind to one of these receptors. Different prototypical tastes have different actions at receptors: salts operate most simply, sodium ions entering neurons to generate ACTION POTENTIAL. Sourness is detected by hydrogen ions binding to and blocking potassium channels (though the sourness of acids is not only a function of hydrogen concentration). Sweet substances—typically but not only sugars—bind to receptors and activate SECOND MESSENGERS, principally CYCLIC AMP. Bitter substances—quinine for instance—activate INOSITOL TRIPHOSPHATE second messenger systems.
Individual Differences in Chemosensory Perception Amongst Cancer Patients Undergoing Chemotherapy: A Narrative Review
Published in Nutrition and Cancer, 2022
Alba Ruiz-Ceamanos, Charles Spence, Jordi Navarra
Smell can be experienced in one of two importantly different ways: orthonasal and retronasal (23, 24). Orthonasal olfaction occurs when we smell external aromas from the environment, while retronasal olfaction occurs when volatile aromatic odor molecules are pulsed out of from the back of the nose, especially when we swallow (e.g., when we eat or drink; see 25, 26). In the latter case, one may note that smell and taste are activated at more or less the same time, thus hindering people’s ability to distinguish between the respective inputs that are attributable to each of the senses. On the other hand, taste (gustation) refers exclusively to what can be distinguished from the stimulation of sensory receptors in the oral cavity that code for basic tastes including bitter, sour, sweet, salt, and umami. These sensations appear when a substance activates certain receptors located in the mouth (though see also 27). Finally, flavor refers to a multisensory perception of food or drink involving not only taste, but also retronasal smell (see 28) and, on occasion, the trigeminal nerve (the nerve responsible for the face and motor functions that provides sensations such as temperature, astringency, or pungency; 29) as well.
Neurological manifestations and pathogenic mechanisms of COVID-19
Published in Neurological Research, 2022
Matteo Galea, Michaela Agius, Neville Vassallo
Gustation is also closely linked with olfaction, as during mastication there is the release of odorants which then bind to the odorant receptors. Indeed, the perception of flavor is actually an amalgamation of olfactory and gustatory sensation [95]. This could potentially imply that the gustatory dysfunction being observed amongst those infected may actually be attributed to the onset of anosmia. In fact, the exact mechanism through which SARS-CoV-2 may cause disruption in taste perception has not been fully elucidated. However, studies have observed a high ACE2 receptor expression on tongue epithelial cells [96]. Moreover, potential activation of toll-like receptors through cytokine release, particularly IL-6 and interferon gamma, may lead to taste bud inflammation and death. This in turn may cause alterations in taste perception.
Representations of the olfactory bulb and tracts in images of the medieval cell doctrine
Published in Journal of the History of the Neurosciences, 2022
For some of the special senses (vision, audition, and gustation), the illustrated linkage between the sensory organ and the sensus communis is straightforward, even if erroneous and simplistic. With vision, for example, an afferent pathway (usually represented as a straight line) typically connects the eye (and, in particular, usually the pupil, where light enters the eye) to the sensus communis. There was, of course, then no conception that the retina is responsible for phototransduction. Similar lines connect the nose (olfaction), ears (audition), and the tongue (gustation) with the sensus communis. Uncommonly, some of the special senses were illustrated as having connections with the middle or posterior ventricle of the brain: For example, German anatomist Johann Dryander showed connections between the pupils and two of the ventricles (the anterior and middle ventricles), and between the tongue and the posterior or third ventricle (Dryandrum 1537).