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Taste and the Chorda Tympani

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... Chorda tympani symptoms (particularly taste alterations and dry mouth) following middle ear surgery are expected in 15 to 22% of patients [99], [100]. Persistent dysgeusia was reported in 2.7 to 12% of cases if the nerve had been preserved, and in 5.3 to 43% of cases if the chorda tympani had been disrupted [101], [102], [103], [104]. At first sight, these values seem to contradict common clinical observations. ...
... At first sight, these values seem to contradict common clinical observations. Ear surgeons often make the experience that postoperative taste disturbance occurs more frequently after intraoperative stretching of the chorda tympani than after a complete transection of the nerve [101], [105], [106], [107], [108], [109]. This observation has been documented in the literature quite early: for instance, only three out of 45 patients reported ageusia following radical mastoidectomy with disruption of the chorda tympani [110]. ...
... In general, taste disturbance is observed more frequently after stapes surgery as compared to middle ear surgery for inflammatory disease (see chapter 3.5.8). For instance, 80% of 126 patients reported taste alterations and a dry mouth following stapes surgery [101]. Moreover, taste disturbance was described in 95% of cases after the chorda tympani had been cut versus 52% if it had been preserved [102]. ...
Article
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Surgery of the ear and the lateral skull base is a fascinating, yet challenging field in otorhinolaryngology. A thorough knowledge of the associated complications and pitfalls is indispensable for the surgeon, not only to provide the best possible care to his patients, but also to further improve his surgical skills. Following a summary about general aspects in pre-, intra-and postoperative care of patients with disorders of the ear/lateral skull base, this article covers the most common pitfalls and complications in stapes surgery, cochlear implantation and surgery of vestibular schwannomas and jugulotympanal paragangliomas. Based on these exemplary procedures, basic “dos and don’ts” of skull base surgery are explained, which the reader can easily transfer to other disorders. Special emphasis is laid on functional aspects, such as hearing, balance and facial nerve function. Furthermore, the topics of infection, bleeding, skull base defects, quality of life and indication for revision surgery are discussed. An open communication about complications and pitfalls in ear/lateral skull base surgery among surgeons is a prerequisite for the further advancement of this fascinating field in ENT surgery. This article is meant to be a contribution to this process.
... Not surprisingly, studies with humans have shown that unilateral CT injury (Bull, 1965;Grant, Miller, Simpson, Lamey, & Bone, 1989;Kveton & Bartoshuk, 1994;Zuniga, Chen, & Miller, 1994;Zuniga, Chen, & Phillips, 1997) or anesthetization (Lehman, Bartoshuk, Catalanotto, Kveton, & Lowlicht, 1995;Yanagisawa, Bartoshuk, Catalanotto, Karrer, & Kveton, 1998) are followed by marked localized taste deficits on the ipsilateral side of the anterior tongue. Zuniga et al. (1994Zuniga et al. ( , 1997 found that repair of a damaged chorda-lingual nerve results in improved performance on citric acid detection and scaling tasks on the ipsilateral anterior tongue over time after CT repair in approximately half of the patients. ...
... Such studies have revealed decreases in the perceived intensities of various compounds, including NaCl, after bilateral CT damage (Shafer, Frank, Gent, & Fischer, 1999) or anesthetization (Catalanotto, Bartoshuk, Ostrom, Gent, & Fast, 1993;Yanagisawa et al., 1998). Additionally, Bull (1965) reported that the loss of all four taste qualities on the side of the anterior tongue ipsilateral to CT injury appeared to be a permanent effect of CTX, and Chilla, Nicklatsch, & Arglebe (1982) noted that dysgeusia persisted on the anterior tongue ipsilateral to CT injury at 4'/2 years postinjury. In our study, all of the rats in the CTX-62R group displayed "recovered" sensitivity to NaCl and had substantial, though reduced, numbers of taste buds on the anterior tongue. ...
Article
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Chorda tympani nerve (CT) transection (CTX) raises sodium chloride (NaCl) taste detection threshold, but the effect of CT regeneration on NaCl threshold is unknown. This experiment examined whether CT regeneration supports normal NaCl threshold in the rat. Thresholds were measured with a 2-lever operant procedure. Thresholds increased more than 1 order of magnitude after CTX regardless of recovery period length. Postsurgical thresholds in rats with regenerated CTs did not differ from presurgical values. Stimulus adulteration with amiloride raised thresholds in rats with intact or regenerated CTs by about 1 order of magnitude but did not raise thresholds beyond postsurgical levels in rats with transected CTs. Thus, the regenerated CT supports normal NaCl threshold, which is raised by amiloride. Because thresholds remained elevated 62 days after CTX when regeneration was prevented, compensatory processes alone cannot support normal NaCl threshold.
... In cases involving CT trauma sustained during otologic surgery, advances in technique have eased the recovery process: Oral sequelae are less frequent when the CT is stretched rather than cut [31][32][33][34][35][36][37] and recovery rates following transection are highest when the cut ends are reattached [38,39]. Still, in these and other cases of CT damage, follow-up taste testing often reveals persistent change and incomplete recovery of function [e.g., 36,40,41]. These results coincide with structural data from patients with sectioned CT nerves: Regeneration occurs in many cases, but microscopy shows significant fibrosis and fewer intact nerve cells [42]. ...
... Oral disinhibiton may explain the phenomenon known as Btaste constancy^, which has been documented as a medical and gastronomic curiosity for at least two centuries: Wholemouth sensation is remarkably impervious to regional nerve loss. Abundant clinical evidence details the rapid decline of anterior taste sensation following CT damage [e.g., 40,41,52,53] and posterior taste and tactile sensation following IX damage [e.g., 54], yet whole-mouth sensation is often unaffected. Taste cues are perceptually referred to sites in the mouth that are touched [55][56][57], so a parsimonious explanation for taste constancy is that regional nerve damage augments remaining taste cues, which are experienced throughout the moutheven in the denervated area, because it is touched during whole-mouth stimulation. ...
Article
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Oral sensations (i.e., taste, oral somatosensation, retronasal olfaction) are integrated into a composite sense of flavor, which guides dietary choices with long-term health impact. The nerves carrying this input are vulnerable to peripheral damage from multiple sources (e.g., otitis media, tonsillectomy, head injury), and this regional damage can boost sensations elsewhere in the mouth because of central interactions among nerve targets. Mutual inhibition governs this compensatory process, but individual differences lead to variation in whole-mouth outcomes: some individuals are unaffected, others experience severe loss, and some encounter sensory increases that may (if experienced early in life) elevate sweet-fat palatability and body mass. Phantom taste, touch, or pain sensations (e.g., burning mouth syndrome) may also occur, particularly in those expressing the most taste buds. To identify and treat these conditions effectively, emerging clinical tests measure regional vs. whole-mouth sensation, stimulated vs. phantom cues, and oral anatomy. Scaling methods allowing valid group comparisons have strongly aided these efforts. Overall, advances in measuring oral sensory function in health and disease show promise for understanding the varied clinical consequences of nerve damage.
... The chorda tympani nerve travels through the middle ear, so it can be damaged during ear surgery or with pathogen exposure and inflammation from middle ear infections. An early case study of middle ear surgery found two of three patients reported depressed taste, flavor and oral chemesthetic experiences [29]. Experimentally anesthetizing the chorda tympani nerve unilaterally shows reduction of taste ipsilaterally and heightened taste sensations contralaterally from CN IX [30,31]. ...
Chapter
Valid measurement of taste is critical for advanced understanding of how variation in taste perception and alterations in taste perception influence dietary behaviors, health, and well-being. Psychophysical procedures exist for measuring the concentration of taste required for detection or recognition, but changes in perceived intensity and liking (hedonic responses) with changes in concentration above threshold are more relevant for diet and health. Here, measures of taste perceived with the whole mouth as well as regional measures of specific taste-related cranial nerve innervation are reviewed. Recommendations and best practices are provided to avoid common mistakes in measuring perceived intensity toward increased ability to understand and document variation in taste and oral sensation. Taste testing is covered for laboratory settings as well as for clinical settings, and for community- and population-level studies.
... Despite nerve integrity, 27% of patients in the present cohort reported subjective post-operative dysgeusia at the early follow-up, and 15% at late follow-up. Similarly, Bull found that overall, 51% of patients whose chorda tympani had been preserved during microscopic stapes surgery had related symptoms, and these symptoms were still present in 7% of patients at 1-year follow-up [12]. Using objective taste assessment tools (a static 2-point discrimination test, an electrostimulator test, and an electromiography before and after stapes surgery), Maeda and colleagues showed that taste disturbance occurred in 51.2% of patients following surgery, even when the nerve was preserved [13]. ...
Article
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Purpose:To investigate how the anatomical configuration of the oval window region (OWR) influences the management of the chorda tympani (ChT) and the curetting of adjacent bony structures, in a setting of patients undergoing endoscopic stapes surgery (EStS); to assess the incidence of early and late post-operative dysgeusia and to identify anatomical and surgical factors influencing taste function after EStS. Methods: Surgical video recordings of 48 patients undergoing EStS for otosclerosis between January 2019 and July 2020 were retrospectively revised, to classify the anatomical variability of selected middle ear structures and the management strategies for the ChT. Clinical records of included patients were reviewed for subjective early and late post-operative taste impairment using a 5-point Likert-scale. Results:The most common configuration of the OWR was type III. The extension of the bony curettage resulted inversely proportional to the exposure of the OWR. The long-term rate of preserved post-operative taste function was 85%. Displacement of the ChT was necessary in 43/48 cases (90%), mostly medially (36/48, 75%). Conclusion: Bone curetting during EStS does not correlate with post-operative taste impairment. Despite 100% ChT preservation rate, dysgeusia may occur in a minority of patients, with no apparent relationship to anatomical variability or intraoperative management of the ChT. The use of CO2 laser could have a role in increasing the risk of post-operative dysgeusia after EStS. link for view-only version: https://rdcu.be/cn033
... The herpetic eruptions outlined the sensory fields of the geniculate ganglion on the tongue, soft palate, and ear. Another basis for evaluating the involvement of the chorda tympani nerve with lingual taste buds came from patients who had undergone middle ear surgery (Borg et al., 1967;Bull, 1965). Contemporary reviews of human (Norgren, 1990;Pritchard and Di Lorenzo, 2015) and primate (Pritchard, 1991) taste pathways have incorporated observations from the second half of the 20th century, particularly those derived from electrophysiological and imaging studies. ...
Chapter
Most animals possess three largely independent chemoreceptor systems that guarantee the integrity of several aspects of “life insurance”, namely the detection of hazardous or required chemical substances. They consist of the gustatory (taste), olfactory (smell), and the trigeminal system. All three senses rely on unique neuroanatomical sensors, either taste receptor cells or olfactory receptor neurons, or free nerve endings of the trigeminal nerve. They are responsible for the initial transduction process that ultimately results in the perception of “odors” in olfaction, and bitter, sour, salty, sweet, and umami sensations in taste, and spicy in trigeminal perception. This chapter describes the anatomy of both the gustatory (taste) and olfactory (smell) systems in humans and gives some historical context for what is presently known about this important pair of sensory systems. Its main focus is on the description of clusters of gustatory chemosensory cells in the oral cavity, known as taste buds, and nasal chemoreceptor locations, their blood and nerve supplies, and the associated salivary glands including details of their microstructure. Taste buds are clusters of 50–100 neuroepithelial cells located in the oral cavity, including the epiglottis and larynx. They function as the initial sentinel for a sensory system to distinguish “dangerous” food components, often regarded as bitter or unpleasant, from “useful” ones, often regarded as pleasant, salty or sweet. Further, the structure of the nasal cavity along with the different mucosa types containing respiratory, transitional, and olfactory epithelium will be described. The olfactory system relates to the detection of volatile stimuli that may bind to a set of almost 400 different receptor types located on cilia of neuroepithelial cells of the nasal cavity.
... The herpetic eruptions outlined the sensory fields of the geniculate ganglion on the tongue, soft palate, and ear. Another basis for evaluating the involvement of the chorda tympani nerve with lingual taste buds came from patients who had undergone middle ear surgery (Borg et al., 1967;Bull, 1965). Contemporary reviews of human (Norgren, 1990;Pritchard and Di Lorenzo, 2015) and primate (Pritchard, 1991) taste pathways have incorporated observations from the second half of the 20th century, particularly those derived from electrophysiological and imaging studies. ...
Chapter
Synopsis The chemical senses taste and olfaction rely on unique neuroanatomical sensors, either taste receptor cells or olfactory receptor neurons. They are responsible for the initial transduction process that ultimately results in the perception of “odors” in olfaction, and bitter, sour, salty, sweet, and umami sensations in taste. This chapter describes the anatomy of both the gustatory and olfactory systems in humans. Its main focus is on the description of intraoral taste buds, and the nasal olfactory mucosa, including their blood and nerve supplies, and some important central nervous relay stations.
... "Metallic" sensations have also been reported in human participants when several different taste modalities are stimulated synchronously; for example, during direct electrical stimulation of the chorda tympani (Frenckner and Preber 1954), and following generalized damage to the chorda tympani, for example following ear surgery (Rice 1963;Bull 1965;Mahendran et al. 2005;Galindo et al. 2009). Following nerve damage in the auditory system, there may be no reduction in auditory cortex activity, suggesting that compensatory amplification has occurred (as reviewed by Roberts 2018). ...
Article
Of all the oral sensations that are experienced, "metallic" is one that is rarely reported in healthy participants. So why, then, do chemotherapy patients so frequently report that "metallic" sensations overpower and interfere with their enjoyment of food and drink? This side-effect of chemotherapy-often referred to (e.g., by patients) as "metal mouth"-can adversely affect their appetite, resulting in weight loss, which potentially endangers (or at the very least slows) their recovery. The etiology of "metal mouth" is poorly understood, and current management strategies are largely unevidenced. As a result, patients continue to suffer as a result of this poorly understood phenomenon. Here, we provide our perspective on the issue, outlining the evidence for a range of possible etiologies, and highlighting key research questions. We explore the evidence for "metallic" as a putative taste, and whether "metal mouth" might therefore be a form of phantageusia, perhaps similar to already-described "release-of-inhibition" phenomena. We comment on the possibility that "metal mouth" may simply be a direct effect of chemotherapy drugs. We present the novel theory that "metal mouth" may be linked to chemotherapy-induced sensitization of TRPV1. Finally, we discuss the evidence for retronasal olfaction of lipid oxidation products in the etiology of "metal mouth." This article seeks principally to guide much-needed future research which will hopefully one day provide a basis for the development of novel supportive therapies for future generations of patients undergoing chemotherapy.
... One way to study these interactions is to explore clinical and experimental data in which taste is diminished. Bull (1965) summarized chemosensory complaints in patients who had undergone stapedectomies (surgery in the middle ear to improve hearing). The chorda tympani taste nerve can be damaged during this surgery because it travels through the middle ear on its way from the tongue to the brain. ...
Article
Full-text available
Aristotle confused taste with flavor because he did not realize that chewing food releases odorants (volatiles) that rise up behind the palate and enter the nose from the rear (retronasal olfaction). When Aristotle bit into an apple, the flavor of the apple was perceptually localized to his mouth so he called it "taste." The correct attribution of flavor to the sense of olfaction was not made until 1812, and the term retronasal olfaction did not come into common use until 1984. Recent research has focused on interactions; tastes can change the perceived intensities of retronasal olfactory sensations and vice versa. In particular, some retronasal olfactory stimuli enhance sweet taste signals in the brain. In addition to sweetening foods (and reducing dependence on sugars and artificial sweeteners), retronasal olfaction can bypass damaged taste nerves and thus perhaps restore sweetness perception in patients. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
... The herpetic eruptions outlined the sensory fields of the geniculate ganglion on the tongue, soft palate, and ear. Another basis for evaluating the involvement of the chorda tympani nerve with lingual taste buds came from patients who had undergone middle ear surgery (Bull, 1965;Borg et al., 1967). Contemporary reviews of human (Norgren, 1990;Pritchard and Di Lorenzo, 2015) and primate (Pritchard, 1991) taste pathways have incorporated observations from the second half of the 20th century, particularly those derived from electrophysiologic and imaging studies. ...
... The herpetic eruptions outlined the sensory fields of the geniculate ganglion on the tongue, soft palate, and ear. Another basis for evaluating the involvement of the chorda tympani nerve with lingual taste buds came from patients who had undergone middle ear surgery (Bull, 1965;Borg et al., 1967). Contemporary reviews of human (Norgren, 1990;Pritchard and Di Lorenzo, 2015) and primate (Pritchard, 1991) taste pathways have incorporated observations from the second half of the 20th century, particularly those derived from electrophysiologic and imaging studies. ...
Chapter
The sense of taste relies on well-defined neuroanatomical structures, namely, the taste buds and afferent nerve fibers. Taste buds are clusters of 50-100 neuroepithelial cells located throughout the oral cavity, including the epiglottis and larynx. They are responsible for the initial transduction process that ultimately results in the perception of bitter, sour, salty, sweet, and umami (savory) sensations. They service as the initial sentinel for a sensory system critical in evolution for distinguishing "dangerous" food components, often perceived as bitter or unpleasant, from "useful" ones, often perceived as pleasant, salty, or sweet. This chapter describes the anatomy and development of the human peripheral taste system and provides historical context for what is presently known about this element of this important sensory system. Its main focus is on the fundamental question of how tastants are perceived-a question that has been of philosophical and scientific interest for more than two millennia. Descriptions of lingual and extralingual taste buds, their blood and nerve supplies, and the associated salivary glands are provided, including details of their microstructure and transduction mechanisms.
... 12,48 Prior reports of middle ear surgery complications have shown that damage to the chorda tympani can result in not only decreased taste, but also in taste phantoms, notably metallic, bitter or salty sensations. 49,50 Studies by Bartoshuk et al 6 Lehman et al 48 and Halpern et al 50 support the theory of increased CN Ⅸ responses in the presence of anesthesia to the chorda tympani nerve, reflecting physiologic compensation to minimize the loss of taste sensation from this branch of CN Ⅶ. In posttonsillectomy dysgeusia cases reported in the past, elevation of EGM threshold in the posterior tongue has been observed. ...
Article
Full-text available
Lingual branches of the glossopharyngeal nerve (CN Ⅸ) are at risk of injury during tonsillectomy due to their proximity to the muscle layer of the palatine tonsillar bed. However, it is unclear how often this common surgery leads to taste disturbances. We conducted a literature search using PubMed, Embase, Cochrane Library, Google Scholar, PsychInfo, and Ovid Medline to evaluate the available literature on post-tonsillectomy taste disorders. Studies denoting self-reported dysfunction, as well as those employing quantitative testing, i.e., chemogustometry and electrogustometry, were identified. Case reports were excluded. Of the 8 original articles that met our inclusion criteria, only 5 employed quantitative taste tests. The highest prevalence of self-reported taste disturbances occurred two weeks after surgery (32%). Two studies reported post-operative chemical gustometry scores consistent with hypogeusia. However, in the two studies that compared pre- and post-tonsillectomy test scores, one found no difference and the other found a significant difference only for the left rear of the tongue 14 days post-op. In the two studies that employed electrogustometry, elevated post-operative thresholds were noted, although only one compared pre- and post-operative thresholds. This study found no significant differences. No study employed a normal control group to assess the influences of repeated testing on the sensory measures. Overall, this review indicates that studies on post-tonsillectomy taste disorders are limited and ambiguous. Future research employing appropriate control groups and taste testing procedures are needed to define the prevalence, duration, and nature of post-tonsillectomy taste disorders.
... This loss of taste typically lateralizes to the left or right side, depending on whether the left or right ear was affected. Yet, individuals are often unaware of this taste loss, as taste sensation from the rest of the mouth is adequate or even augmented to mask the loss [13,14]. Nonetheless, it is possible that individuals with taste loss on the anterior tongue would exhibit even greater differences in intensity between the sip and spit and sip and swallow conditions, and these individuals could be driving the overall pattern of responses. ...
Article
While the myth of the tongue map has been consistently and repeatedly debunked in controlled studies, evidence for regional differences in suprathreshold intensity has been noted by multiple research groups. Given differences in physiology between the anterior and posterior tongue (fungiform versus foliate and circumvallate papillae) and differences in total area stimulated (anterior only versus whole tongue, pharynx, and epiglottis), small methodological changes (sip and spit versus sip and swallow) have the potential to substantially influence data. We hypothesized instructing participants to swallow solutions would result in greater intensity ratings for taste versus expectorating the solutions, particularly for umami and bitter, as these qualities were previously found to elicit regional differences in perceived intensity. Two experiments were conducted: one with model taste solutions [sucrose (sweet), a monosodium glutamate/inosine monophosphate (MSG/IMP) mixture (savory/umami), isolone (a bitter hop extract), and quinine HCl (bitter)], and a second with actual food products (grapefruit juice, salty vegetable stock, savory vegetable stock, iced coffee, and a green tea sweetened with acesulfame-potassium and sucralose). In a counterbalanced crossover design, participants (n=66 in experiment 1 and 64 in experiment 2) rated the stimuli for taste intensities both when swallowing and when spitting out the stimuli. Results suggest swallowing may lead to greater reported bitterness versus spitting out the stimulus, but that this effect was not consistent across all samples. Thus, explicit instructions to spit out or swallow samples should be given to participants in studies investigating differences in taste intensities, as greater intensity may sometimes, but not always, be observed when swallowing various taste stimuli.
... Metallic sensations have also been reported as a side effect of drugs (27) and throughout pregnancy (28). Moreover, metallic taste might be elicited by oral yeast infections (29), burning mouth syndrome (30), damage by stapedectomy or anesthesia of the chorda tympani (31,32), artificial sweeteners (33), and dental amalgam fillings (34). These factors may have influenced the prevalence of metallic taste in the current study. ...
Article
Full-text available
A metallic taste is reported by cancer patients as a side effect of systemic therapy. Despite the high prevalence, this taste alteration has received limited attention. The present study investigated: 1) the prevalence of metallic taste in cancer patients treated with systemic therapy; 2) possible predictors of metallic taste; and 3) characteristics of metallic taste. A heterogeneous population of 127 cancer patients, who had received systemic treatment in the past year or were still on treatment, completed a questionnaire developed for this study. Fifty-eight of 127 (46%) patients reported taste changes in the preceding week. Of these patients, 20 (34%) reported a metallic taste. Patients treated with chemotherapy, concomitant radiotherapy, as well as targeted therapy reported metallic taste. Women experienced metallic taste more often than men. Patients experiencing a metallic taste also reported more frequently that they were bothered by sour food and that everything tasted bitter. The experience of metallic taste was highly variable among patients. In conclusion, metallic taste is a frequently experienced taste alteration by cancer patients. Patients treated with chemotherapy, concomitant radiotherapy, and targeted therapy are all at risk for this taste alteration. However, not all patients reported this alteration as bothersome.
... While the latency of this activation appears rather fast, it reflects unlikely a purely lingual somatosensory response as this would occur much earlier at latencies of around 10-60 ms and more pronounced over the contralateral hemisphere. The average current intensity used for taste stimulation was several-fold below the intensity needed to activate trigeminal fibers as shown in electrophysiological studies in ro-dents (Pfaffmann, 1980;Bujas et al., 1979;Yamamoto et al., 1980) and clinical studies in humans (Bull, 1965). "However, trigeminal fibers convey not only tactile and thermal but also gustatory information and are also found in taste buds. ...
Thesis
Die sensorischen und hedonischen Eigenschaften von Essen sind wichtige Einflussfaktoren für die Nahrungsauswahl und –aufnahme. Was macht die Anziehungskraft von Nahrungsreizen aus? Die sensorischen und hedonsichen Eigenschaften von Nahrungsreizen werden mit allen Sinnen, oftmals sogar gleichzeitig, verarbeitet. Nahrungswahrnehmung ist damit ein mutlisensorisches Phänomen. Der Geruch, der Anblick, der Tasteindruck oder Geräusche können bereits vor der Nahrungsaufnahme wahrgenommen werden und Erwartungen hinsichtlich des Geschmacks auslösen. Diese prä-ingestiven Wahrnehmungseindrücke spielen daher auch eine maßgebliche Rolle bei der Entstehung von Verlangen und Gelüsten. Während der Nahrungsaufnahme, beim Kauen und Schlucken, spielen die chemischen Sinne, Schmecken und Riechen, eine besondere Rolle. Der Gesamtsinneseindruck aus den chemischen Sinneskanälen wird auch als Flavor bezeichnet. Wobei angemerkt sein soll, dass auch nicht-chemische Sinne, Sehen, Hören und Tasten, in die Flavordefinition einbezogen werden können. Zweifelsohne stellt die Nahrungsaufnahme ein komplexes Verhalten dar, das perzeptuelle, kognitive und Stoffwechselprozesse gleichermaßen umfasst. Die vorliegende Habilitationsschrift widmet sich der Untersuchung der neurokognitiven Mechanismen der visuellen, gustatorischen und flavour Wahrnehmung von Nahrungsobjekten und umfasst Untersuchungen zur Vulnerabilität der neuronalen Repräsentationen durch kontextuelle Reize. Zusammenfassend schließt die Arbeit mit der Feststellung, dass ein umfassendes Verständnis der psychophysiologischen Mechanismen der sensorischen und hedonischen Verarbeitung von Nahrungsreizen über alle Sinne die perzeptuelle Grundlage für nahrungsbezogenes Urteilen und Entscheiden darstellt.
... This loss of taste typically lateralizes to the left or right side, depending on whether the left or right ear was affected. Yet, individuals are often unaware of this taste loss, as taste sensation from the rest of the mouth is adequate or even augmented to mask the loss [13,14]. Nonetheless, it is possible that individuals with taste loss on the anterior tongue would exhibit even greater differences in intensity between the sip and spit and sip and swallow conditions, and these individuals could be driving the overall pattern of responses. ...
Article
Saliva is becoming an increasingly useful research material across multiple fields of inquiry, including biomedical, dental, psychological, nutritional, and food choice research. However, both the flow rate and protein composition of stimulated saliva differ as a function of the collection method. We hypothesized that the context in which a stimulus is presented to participants may alter salivation via top down cognitive effects and/or behavioral changes (i.e., spitting efficiency). We presented participants with one stimulus (commercially available green tea) in two distinct contexts, once where the tea was described as a food item (“tea”) and once where it was described as a disgusting non-food item (“rabbit hair extract”). Saliva and the expectorated stimulus were collected following 15 s of oral exposure in a crossover design with the identical stimulus presented in both contexts; saliva was also collected for 5 min after stimulation while chewing a piece of wax. Participants also completed validated personality instruments to measure food involvement, sensation seeking, sensitivity to reward, and sensitivity to punishment. Our data suggest participants spat out more sample when told they received the ‘non-food’ stimulus compared to the ‘food’ stimulus, particularly when they were given the non-food stimulus first. Further, individuals who were higher in sensation seeking spat out more sample during the ‘food’ condition compared to individuals with lower sensation seeking scores, but this difference was absent in the ‘non-food’ condition. While consistent with a top down cognitive effect on salivary flow, we believe a greater motivation to spit out the ‘non-food’ stimulus is a more likely explanation. In either case, it is clear the context in which a stimulus is presented alters how much sample/saliva is expectorated, suggesting context needs to be carefully considered in future work on salivary flow.
... The herpetic eruptions outlined the sensory fields of the geniculate ganglion on the tongue, soft palate, and ear. Another basis for evaluating the involvement of the chorda tympani nerve with lingual taste buds came from patients who had undergone middle ear surgery (Borg et al., 1967;Bull, 1965). Contemporary reviews of human (Norgren, 1990;Prichard, 2011) and primate (Pritchard, 1991) taste pathways have incorporated observations from the second half of the twentieth century, particularly those derived from electrophysiological studies. ...
Article
This chapter provides sufficient knowledge on peripheral gustatory anatomy. Taste buds occur in distinct papillae of the tongue, the epithelium of the palate, oropharynx, larynx, and the upper esophagus. Lingual taste buds are found exclusively within gustatory papillae, that is, those bearing taste buds. The gustatory papillae include the vallate, foliate, and fungiform papillae. In addition to taste buds and free nerve endings, the solitary chemosensory cells (SCC) comprise another chemosensory system in vertebrates. One of the most intriguing challenges for suggesting possible functional properties of taste bud cells is to identify subsets of cells by morphological features and molecular properties, many of which can be traced even in enriched primary taste bud cell cultures. The observation that taste buds degenerate after dissection of their sensory innervation and, subsequently, reappear after regeneration of their peripheral nerves has been a major focus of research in the peripheral taste system.
... As has already been noted, the loss of smell is often identified by those affected as a loss of taste (Bull, 1965). For instance, blocking the nose (as when one has a heavy cold) dramatically reduces what one believes that one can taste. ...
Chapter
Full-text available
People’s use of the terms ‘taste’ and ‘flavour’ is often confusing, both in everyday use and in the academic literature. Failure to distinguish these ‘basic’ terms is likely to slow the development of our understanding of the chemical senses, currently a rapidly growing area of study in perception science. Our aim here is to defend the idea that, ultimately, it doesn’t make sense to treat experiences of the putative basic tastes, such as ‘sweetness’ and ‘sourness’ in our everyday experience as tastes. Rather, we suggest, the evidence supports the view that they should be treated as flavours, just like ‘fruity’ or ‘meaty’. Here we highlight the pervasive nature of the confusion between tastes and flavours, and outline a number of reasons for its occurrence, linked to the topics of attention and oral referral. We then provide psychological, physiological, and philosophical reasons to support the stance that tastes should be classified as a sub-component of flavours and show how doing so helps to dissolve certain debates.
Chapter
The nerve supply to the major salivary glands exists in an overcrowded anatomic area. The head and neck area is replete with a vast cramped neurologic network. Therefore, operating within the limited anatomic confines of the head and neck, not in the immediate vicinity of the major salivary glands, the surgeon may inadvertently injure a neurologic structure as it travels to a salivary gland. Disruption in normal gland function is the end result. Damage to the chorda tympani nerve during stapes surgery will cause a decrease in submandibular and sublingual gland salivary volume. Furthermore, salivary gland surgical procedures that involve the parotid gland may disrupt a nerve’s ability to stimulate the parotid gland (auriculotemporal syndrome) or the paraglandular musculature (facial nerve palsy).
Article
Electrogustometry (EGM) is a practical way to test taste. It is typically performed using unipolar electrodes, with the anode on the tongue and the cathode on the hand, forearm, or neck. This results in electric current passing through non-taste tissues and adds a level of impracticality to its clinical application. We compared, using a repeated measures counterbalanced design, anodal thresholds from a unipolar electrode to those of a unique bipolar electrode in which the anode and cathode are contiguously located. Both sides of the anterior tongue were assessed in 70 subjects, as were the effects of age and sex. Non-parametric analyses were performed. The median threshold of the bipolar electrode's central disk (2.49 µA) did not differ from that of the unipolar electrode (2.96 µA) (p=0.84). On average, older persons exhibited higher thresholds. No significant sex or tongue side effects were evident. Interestingly, when the annular (donut-shaped) bipolar electrode served as the anode, the threshold was higher than that of the other electrodes (5.19 µA; ps<0.001). This conceivably reflected lessened summation of activity among adjacent afferents and partial sampling of tongue regions with fewer taste buds. Correlations among all EGM thresholds were nominally higher for women than for men, ranging from 0.83 to 0.85 for women and 0.54 to 0.67 for men; all ps<0.001). This study validates the use of a bipolar electrode for assessing taste function, averting movement of current through non-taste-related tissues and making such testing safer and more practical.
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Disorders of smell, taste, and oral somatosensation (irritation, touch, temperature, pain) challenge the ability to consume safe and healthy diets as well as enjoy eating and food-related behaviors. From nationally representative US health monitoring, these disorders are as prevalent as hearing or vision disorders. Olfactory dysfunction is most common among older adults, although aging itself may not be the cause. Primary causes of olfactory dysfunction are sensorineural (e.g., chronic nasal/sinus disease, head trauma, respiratory tract infections) and neurodegenerative (e.g., Alzheimer’s disease). Less vulnerable to loss is taste, especially at levels experienced while eating. Individuals can suffer distorted or phantom sensations (i.e., dysgeusia) related to medications or conditions that disrupt normal interactions between cranial nerves that mediate taste sensation. Oral sensation (integrated taste, retronasal olfaction, and oral somatosensation) can be altered in systemic diseases (e.g., chronic kidney disease), especially if control is poor; by medications that treat and manage systemic diseases (e.g., cancer); and with poor oral health. Normal variation in taste associates with differences in food preferences and nutritional status, including obesity, while chemosensory disorders, if severe enough, can alter dietary patterns leading to weight gain or weight loss. Excessive alcohol consumption and chronic smoking increase the risk of chemosensory disorders directly or indirectly through exposures/conditions that, in turn, cause these disorders. Individuals with chemosensory disorders should have full medical evaluation, including assessment of the impact on eating behaviors, diet quality, and nutritional status. Access to healthcare and medical advances hold continued promise toward prevention and treatment of chemosensory disorders.
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Introduction: Iatrogenic injury to the chorda tympani (CT) is a well recognized, although potentially underestimated, consequence of stapes surgery. This study aims to review the currently available literature to determine the incidence and prognosis of taste disturbances in these patients. Data sources: PubMed, Embase, and Cochrane Library databases. Methods: Databases were searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Search terms included (chorda tympani OR gustatory OR taste OR chemosensory OR dysgeusia OR nervus intermedius) AND (ear surgery OR middle ear OR stapes OR stapedectomy OR stapedotomy). Patients with prospective data collection including preoperative data were further divided by methodology into "objective" and "subjective" assessments of taste dysfunction. A systematic review was performed for all included studies, with meta-analysis using a random-effects model was used for those with comparable methodology and patient populations. Results: Initial search yielded 2,959 articles that were screened according to inclusion and exclusion criteria. Once duplicates were removed, seven studies were identified, representing 173 patients with subjective testing (all seven studies) and 146 with objective testing (five studies). Eighty of 173 patients (46.2%) noted a disturbance in taste at early follow-up, whereas as 26 of 173 (15.0%) noted long-term problems. Objective methodology and result reporting were heterogenous and not amenable to pooled meta-analysis for all studies included. Conclusion: Changes in taste occur relatively frequently after stapedectomy. Surgeons should continue to counsel prospective patients as to the risks of both short- and long-term taste disturbances.
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The alleged ability of taste afferents to induce taste buds in developing animals is investigated using a mouse model with a targeted deletion of the tyrosine kinase receptor trkB for the neurotrophin BDNF. This neurotrophin was recently shown to be expressed in developing taste buds and the receptor trkB has been shown to be expressed in the developing ganglion cells that innervate the taste buds. Our data show a reduction of geniculate ganglion cells to about 5% of control animals in neonates. Degeneration of ganglion cells starts when processes reach the central target (solitary tract) but before they reach the peripheral target (taste buds). Degeneration of ganglion cells is almost completed in trkB knockout mice before taste afferents reach in control animals the developing fungiform papillae. Four days later the first taste buds can be identified in fungiform papillae of both control and trkB knockout mice in about equal number and density. Many taste buds undergo a normal maturation compared to control animals. However, the more lateral and caudal fungiform papillae grow less in size and become less conspicuous in older trkB knockout mice. No intragemmal innervation can be found in trkB knockout taste buds but a few extragemmal fibers enter the apex and end between taste bud cells without forming specialized synapses. Taste buds of trkB knockout mice appear less well organized than those of control mice, but some cells show similar vesicle accumulations as control taste bud cells in their base but no synaptic contact to an afferent. These data strongly suggest that the initial development of many fungiform papillae and taste buds is independent of the specific taste innervation. It remains to be shown why others appear to be more dependent on proper innervation.
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Synopsis Taste plays an undisputed role in the sensory analysis of food, and it ensures the identification of nutrients and harmful constituents. This chapter focuses on the perceptual basis of taste and its cortical representations in humans. Because taste seldomly occurs in isolation during eating and drinking, it has been considered to be inherently multisensory. To address this, an excursion is made to the confusion of taste and smell as well as to the role of visual food perception, which is a potent predictor of taste and food appreciation.
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Cognitive Changes and the Aging Brain - edited by Kenneth M. Heilman December 2019
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This chapter examines how taste and flavor help us survive. Omnivores (like humans) face a dilemma; we must select healthy foods and avoid poisons. An early belief in the innate ability to eat a healthy diet (“wisdom of the body”) gave way to our current understanding that taste is the true nutritional sense. A few simple substances (salt, glucose) necessary to solve immediate nutritional problems (sodium deficiency, low blood glucose) produce hard‐wired liking. Most poisons are bitter and we are hard‐wired to dislike them. Food flavor is a combination of taste and retronasal olfaction (odor volatiles perceived from the mouth). Retronasal olfactory stimuli are liked or disliked primarily through association with positive (e.g., calories) or negative (e.g., nausea) biological states. Unfortunately, hard‐wired and acquired liking can lead to nutritional disorders. Taste evolved to help us survive, but can also lead to overeating with attendant health risks.
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This chapter explores the numerous ways that patients present to their physician with taste complaints and what those complaints may imply. It provides an approach to obtaining a taste-focused medical history, physical exam, and sensory evaluation. The chapter presents the gamut of clinical disorders, across multiple specialties, that can be associated with taste disturbance. It discusses clinically-relevant anatomy and physiology associated with taste in the context of specific taste disorders, and suggests options for patient management. Taste dysfunction resulting from trauma is much less common than post-traumatic smell dysfunction, with solitary ageusia of one or more primary taste modalities occurring in less than 1% of persons with major head injury. The ability to taste reflects the proper function of many systems within the body, and as such, may be considered a marker for good health.
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Narrowly viewed, taste is limited to sweet, salt, sour, bitter and savory/umami sensations. Perceptually, taste combines with other sensory inputs to produce complex flavor sensations from ingested stimuli (e.g., foods, beverages, medications, tobacco products). Progress in psychophysics—the study of relationships between physical stimuli and perceptual experiences—permits characterization of normal variation and variation associated with damage or exposures. Psychophysical methods allow us to fully understand genetic, molecular and neurochemical processes involved in taste sensation. Via psychophysics, we can measure how taste variation influences our preferences for and behaviors toward ingested stimuli, and ultimately our health and quality of life.
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Purpose: To demonstrate that sonic hedgehog (Shh) is present in human parotid saliva and is decreased in human taste dysfunction. Methods: Shh was measured in parotid saliva of 27 normal subjects and 81 patients with taste dysfunction of multiple etiologies by use of a sensitive spectrophotometric ELISA assay. Taste dysfunction was defined clinically by both subjective decreases of taste acuity and flavor perception and by impaired gustometry. Results: Shh was found in parotid saliva in both normal subjects and in patients with taste dysfunction. Levels were significantly lower in patients than in normal subjects. Both subjective loss of taste acuity and flavor perception and impaired gustometry was measured in untreated patients. Conclusions: This is the first demonstration of Shh in human saliva. Since Shh has been related to taste bud growth and development its presence in saliva is consistent with its role as a cell signaling moiety involved with stimulation of taste bud stem cells to generate taste receptors. Decreased saliva Shh secretion can be considered a marker of taste dysfunction in patients with multiple pathologies for their dysfunction. This article is protected by copyright. All rights reserved.
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There is a remarkable gap between the importance of taste for man and its clinical consideration which is evident not only in the limited diagnostic potential and the unsatisfactory differential diagnostic analysis of taste disorders but also in the inferior rank given to taste in the medical opinion and the carelessness of some surgeons with the chorda tympani in middle ear operations. Fortunately, taste as a phylogenetically seen old sense is little affectable against lesions of different kinds.
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Patients often fail to notice taste loss even when their taste systems are severely damaged. Pfaffmann [1,2] presented his own case of Ramsey-Hunt’s syndrome (cranial nerve damage produced by the virus responsible for chicken pox) at a meeting of the Association for Chemoreception Sciences. The virus destroyed taste on the left side of his mouth yet he had no subjective awareness of loss in everyday taste experience.
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Unter Geschmack im wissenschaftlichen Sinn verstehen wir die Wahrnehmung der vier Grundgeschmäcke Süß, Salzig, Sauer, Bitter und ihrer Mischungen. Der adäquate Reiz für die Geschmacksinneszellen sind wasserlösliche chemische Substanzen. Sowohl in organischen als auch anorganischen Stoffklassen trifft man Substanzen aller vier Geschmacksqualitäten. Die vier Qualitäten können prinzipiell überall wahrgenommen werden, wo Geschmacksinneszellen vorhanden sind, d. h. auf der Zunge, wesentlich spärlicher am Gaumen, im Pharynx, an der Epiglottis und an den Aryhöckern. Funktionell, aber auch für die Geschmacksuntersuchung spielen die Geschmacksknospen in den Zungenpapillen die entscheidende Rolle. In der Praxis wird die Geschmacksfunktion mit zwei verschiedenen Methoden als Schwellenmessung getestet
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The effectiveness of stapedectomy is well proven, producing an immediate success rate of 97,5–98% but complications do occur even with the most expert surgery. Total loss of hearing in the operated ear has a reported incidence of 0,6–4%.1,2,3Less severe degrees of sensorineural hearing loss as a consequence of cochlear damage during or after surgery occur in 1,4%.1Conductive hearing loss follows 5% of stapedectomies perhaps long after a succesful operation.4 Other complications such as perforation of the tympanic membrane, alteration of taste and facial palsies are briefly considered.
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Numerous oral sensations contribute to the flavor experienced from foods. Texture is sensed throughout the mouth by nerve endings in the oral epithelium. Chemesthetic sensations, including irritation, spiciness, and chemical burn or cooling, are sensed by these same nerves. Tastes are sensed by taste buds, primarily on the tongue, which transduce information through the gustatory nerves. Even after placing food in the mouth, odor is still experienced through retronasal olfaction, the air that passes through the rear of the oral cavity into the nasal passages. All of these sensations combine to give an overall experience of flavor. In individuals with dysphagia, these oral sensory systems can be used to improve swallowing function. Texture is the most common current approach, but the other oral sensations, particularly chemesthesis, may also hold potential for making sensory modified foods for dysphagia management. However, modifying any of these sensory properties also alters the overall food flavor, which can lead to decreased liking of the food.
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This chapter presents a study on anosmia, ageusia, and other disorders of chemosensation. The chapter provides the nomenclature used to characterize disorders of tasting and smelling, examines a number of commonly encountered chemosensory pathologies, and describe up-to-date means for quantitatively assessing, managing, and treating taste and smell disorders. Disorders of the chemical senses are varied, ranging from phantom sensations that appear in the absence of any obvious stimuli to altered or reduced sensations in response to modality-appropriate stimuli. Anosmia reflects the inability to perceive odors, whereas ageusia reflects the inability to perceive tastants. Such losses can be for all modality-specific stimuli or for just some such stimuli. Lessened function for odorants or tastants are termed hyposmia or hypogeusia respectively, and can be further subdivided, on the basis of quantitative testing, into mild, moderate, and severe categories. Hypergeusia or hyperosmia reflects abnormally heighted taste or smell sensations, whereas taste or smell agnosia reflects the inability to recognize a taste or smell sensation even though sensory processing, language, and general intellectual functions are essentially intact, as in some stroke patients. Distorted smell sensationsare termed dysosmias or parosmias, whereas distorted taste sensations are termed dysgeusias or parageusias. Proper oral hygiene and routine dental care are of paramount importance for proper chemosensory function. The chapter discusses natural course of olfactory disorders, natural course of taste disorders, principles of therapy, and others.
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In 1754, a quarter of a century before Galvani’s experiments with frogs’ legs, Sulzer had described the way in which taste was induced by two different, interconnected metals touched by the tongue (lead-silver). As each of these metals by itself is tasteless, Sulzer assumed that when in contact, in one of them or in both, there occurred a vibration of the most minute particles, affecting the tongue nerves. He described the taste produced as being like that of ferro-sulphate. The same phenomenon was rediscovered by Volta (1792) who ascribed it to electric fluid flowing through the tissue from one metal to another and affecting on its way taste nerves. In his numerous experiments carried out in the “bipolar” and later “unipolar” situations, Volta found that taste depended upon the kind of metal touching the tongue. If the positive pole was at the tip of the tongue, the taste was definitely sour, and when the negative pole was in that place, the taste was “…no longer sour but more alkaline, sharp, nearing bitter.” In addition to various tastes observed at the positive and negative pole, Volta remarked that the taste lasted throughout the whole time of the current flow; that in the course of that period taste intensity went up, and that at the negative pole the weak indistinct taste was associated with the sensation of tingling and burning.
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How accurately can the electrically evoked taste threshold be determined? Why have standards of normal values not yet been generally accepted? In order to answer these questions, 80 normal subjects were examined by means of the method of adjustment. The results showed a greater variability of threshold values and side differences than found by other authors. In explanation, it is suggested that the method of adjustment minimizes the biasing effect of the examiner, which normally leads to an underestimation of the threshold variability as well as of the side differences. The method of adjustment is therefore suitable for certain experimental purposes. For clinical use, a simple procedure like Krarups should be preferred. Due to its limited validity, however, only side differences of 100% or more should be considered pathological. A log-scale with rather large units (25% increment steps) is recommended.
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The use of the human senses to distinguish good water from bad, such as by taste, smell, and appearance, is a basic means of self preservation. This chapter points out that the senses are not always a failsafe marker for the safety of water. While some odors are found to be specifically produced by anaerobic conditions and waste discharges, others come from natural organic matter and nuisance algal growth. In modern times, a safe water supply is provided through a multiple barrier concept. The goal of treatment is to eliminate microbial pathogens, control nuisances, and produce biologically and chemically stable potable water. One approach to control the taste and smell of drinking water is through a quality control program that assesses the processes and controls at a water utility. Leaking underground gasoline storage tanks can contaminate private and public ground water supplies with methyl tertiary butyl ether (MTBE).
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In order to study taste disturbances in diabetes mellitus, electrogustometry was carried out in 158 diabetics and compared with that in 1,029 normal subjects. Taste abnormalities were noted in 26% of the diabetic group. Comparison of these results with the knee jerk revealed a significantly more frequent taste abnormality in those with a decreased or absent knee jerk than in those with a normal reflex (p<0.01). In the case of precoma, a marked improvement in taste threshold was noted along with the improvement of the blood sugar value. In order to study the relationship between taste abnormality and the disease picture of diabetes mellitus, changes of lingual papillae and lingual blood vessels were photographed, and angiography of the lingual blood vessels was attempted for a more detailed study. According to these results, the lingual papillae of diabetics are frequently flattened which is in agreement with the findings after disruption of the innervating chorda tympani. Such flattening of lingual papillae appears to be due to diabetic neuropathy, in view of the relationship of such findings to the abnormality in the electrogustometry. The blood vessels within the lingual papilla are distributed more coarsely than in normal subjects, with irregular loops, torsion and tortuosity of the blood vessels. Angiography revealed findings suggesting aneurysm. In order to study the diabetic microangiopathy in the tongue further, histological findings were examined during autopsies. In the small blood vessels of the tongue, hyaline like intimal thickening with PAS positive substance was found, confirming the presence of microangiopathy in the tongue.
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Much has been discovered over the last few decades about the anatomy and physiology of the human taste system, most notably its receptor mechanisms and intermodal factors that influence its function. While the taste system works in concert with the olfactory, somatosensory, auditory, and visual sensory systems to establish the overall gestalt of flavor, its primary specialization is to ensure that the organism obtains energy, maintains proper electrolyte balance, and avoids ingestion of toxic substances. Despite its focus on inborn functions, taste—like its sister sense of smell—is remarkably malleable, reflecting the need to adapt to changing circumstances and general nutrient availability. It is now widely appreciated that taste dysfunction is common in many diseases and disorders, and is a frequent side effect of a number of medications. This interdisciplinary review examines salient aspects of the human gustatory system, including its anatomy, physiology, and pathophysiology. WIREs Cogn Sci 2012, 3:29–46. doi: 10.1002/wcs.156 For further resources related to this article, please visit the WIREs website.
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Metallic taste is a taste alteration frequently reported by cancer patients treated with chemotherapy. Attention to this side effect of chemotherapy is limited. This review addresses the definition, assessment methods, prevalence, duration, etiology, and management strategies of metallic taste in chemotherapy treated cancer patients. Literature search for metallic taste and chemotherapy was performed in PubMed up to September 2014, resulting in 184 articles of which 13 articles fulfilled the inclusion criteria: English publications addressing metallic taste in cancer patients treated with FDA-approved chemotherapy. An additional search in Google Scholar, in related articles of both search engines, and subsequent in the reference lists, resulted in 13 additional articles included in this review. Cancer patient forums were visited to explore management strategies. Prevalence of metallic taste ranged from 9.7% to 78% among patients with various cancers, chemotherapy treatments, and treatment phases. No studies have been performed to investigate the influence of metallic taste on dietary intake, body weight, and quality of life. Several management strategies can be recommended for cancer patients: using plastic utensils, eating cold or frozen foods, adding strong herbs, spices, sweetener or acid to foods, eating sweet and sour foods, using 'miracle fruit' supplements, and rinsing with chelating agents. Although metallic taste is a frequent side effect of chemotherapy and a much discussed topic on cancer patient forums, literature regarding metallic taste among chemotherapy treated cancer patients is scarce. More awareness for this side effect can improve the support for these patients. Copyright © 2014 Elsevier Ltd. All rights reserved.
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To evaluate whether regenerated fungiform taste buds after severing the chorda tympani nerve can be detected by confocal laser scanning microscopy in vivo. Retrospective study. University hospital. Six patients with a normal gustatory function (Group 1), 9 patients with taste function recovery after severing the CTN (Group 2), and 5 patients without taste function recovery (Group 3) were included. In Groups 2 and 3, canal wall up (closed) tympanoplasty or canal wall down with canal reconstruction tympanoplasty was performed in all patients. Diagnostic. The severed nerves were readapted or approximated on the temporalis muscle fascia used to reconstruct the eardrum during surgery. Preoperative and postoperative gustatory functions were assessed using electrogustometry. Twelve to 260 months after severing the CTN, the surface of the midlateral region of the tongue was observed with a confocal laser microscope. EGM thresholds showed no response 1 month after surgery in all patients of Groups 2 and 3. In Group 2, EGM thresholds showed recovery 1 to 2 years after surgery and before confocal microscopy (-1.3 ± 6.5 dB). There was a significant difference between Group 1 (-5.7 ± 2.0 dB; p < 0.01) and Group 2. In Group 3, EGM thresholds showed no response for more than 2 years. In the control group (Group 1), 0 to 16 taste buds were observed in each FP, and 55 (79.7%) of 69 FP contained at least 1 taste bud. The mean number of taste bud per papilla was 3.7 ± 3.6. In patients with a recovered taste function (Group 2), 0 to 8 taste buds were observed in each FP. In this group, 54 (56.2%) of 94 FP contained at least 1 taste bud. The mean number of taste bud per papilla was 2.0 ± 2.2 (p < 0.01). In Group 3, without recovery, the FP was atrophied, and no taste bud was observed. Regenerated fungiform taste bud could be observed in vivo using confocal laser scanning microscopy, indicating that regenerated taste bud can be detected without biopsy.
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Flavour results primarily from the combination of three discrete senses: taste, somatosensation and olfaction. In contrast to this scientific description, most people seem unaware that olfaction is involved in flavour perception. They also appear poorer at detecting the olfactory components of a flavour relative to the taste and somatosensory parts. These and other findings suggest that flavour may in part be treated as a unitary experience. In this article, I examine the mechanisms that may contribute to this unification, in particular the role of attention. Drawing on recent work, the evidence suggests that concurrent gustatory and somatosensory stimulation capture attention at the expense of the olfactory channel. Not only does this make it hard to voluntarily attend to the olfactory channel, but it also can explain why olfaction goes largely unnoticed in our day-to-day experience of flavour. It also provides a useful framework for conceptualizing how the unitary experience of flavour may arise from three anatomically discrete sensory systems.
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Introduction: Damage to the chorda tympani nerve is frequent during otologic surgery. This article studies the clinical outcomes of the nerve's section versus its conservation in otosclerosis surgery.Material and method: Retrospective observational study using our department's otosclerosis database and a validated questionnaire on symptoms associated with the chorda tympani nerve. The sample was divided into two groups: section and conservation (patients whose nerve was anatomically conserved). We studied the presence and duration of symptoms, the surgical technique and the audiometric results.Results: 78 patients (88 ears): section group (18 ears; 20 %) and conservation group (70 ears; 80 %). Overall, gustatory symptoms appear in 35 % (39 % section group; 34 % conservation group). Differences between groups are not statistically significant in relation to presence and duration of symptoms, surgical technique or audiometric results. Only 1 patient in each group reports long-term symptoms. Our results suggest there are no major clinical differences following section versus conservation of the chorda tympani nerve. A wide range of factors such as age, presence of previous middle ear pathology, cross innervation and gastronomic culture may play a role in the appearance of symptoms.Conclusions: Symptoms appearing after iatrogenic damage to the chorda tympani nerve have, in general, little clinical relevance, especially in the long term, regardless of whether the nerve is dissected or manipulated to various degrees.
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In 1822, Francois Magendie after dividing the trigeminal nerve within the skull in dogs made the following statement: "The question of taste, formerly so obscure, no longer presents any difficulty. Physiological experiments and pathological observations have solved it. If the trunk of the fifth nerve is divided in the skull, taste is completely lost, even for sour and bitter substances. This total loss of taste has been noticed in persons in whom the fifth nerve has been compressed or altered." The problem of taste was not, however, to be settled so simply and unequivocally.As it has been impossible to expose the nerves concerned in the mediation of taste sensations throughout their courses, indirect methods of study, such as the following, have been employed: (1) clinical studies checked by pathologic observations, (2) experiments on animals and (3) postoperative observations on human beings. From the evidence which has accumulated, one theory
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Thesis (M.S. (Med.) in Otolaryngology)--Graduate School of Arts and Sciences, University of Pennsylvania, 1937. Bibliography: l. 41-42.
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The construction of an apparatus for electrical taste stimulation for clinical use is described. Investigations were carried out on 140 normal persons to determine the gustatory thresholds by an electric stimulus on the right and left sides of the anterior and posterior parts of the tongue. The results show that the thresholds in all age groups vary within very wide ranges, while there is no significant difference in thresholds determined on the right or left sides of the tongue. The method would appear to yield better results than does a semi-quantitative test using taste solutions of different concentrations.
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A clinical quantitative test of taste is described. It employs Beebe-Center's standards for use of the gust scale in measuring subjective taste strength. The test is both valid and reliable (test-retest reliability is of the order of 0.8 for the anterior part of the tongue) and the distribution of the results is known. The mean threshold for sucrose and sodium chloride appears to be approximately normally distributed when expressed in log gusts and, on such a scale, to be linearly related to age. There appears to be a secondary depression of the threshold in women around the age of thirty years.
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An account is given of investigations into the gustatory functions of 50 patients suffering from Bell's palsy. The aims of these investigations were: in the first instance to compare the results obtained from a newly described electrogustometric technique with the results from those techniques more generally adopted in gustatory determinations, and secondly to estimate the clinical importance of gustatory determinations partly for prognosis of the complaint and partly for topical diagnosis of peripheral facial nerve palsy.
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In stapes surgery, the chorda may be stretched or cut to improve visualization of the footplate. There have been many instances of subjective and qualitative taste changes postoperatively. By means of a modified electronic gustometer, we compared changes in taste threshold before and after surgery and related them to reports of trauma to the nerve. Recent texts describe as many as 5 alternate pathways for taste impulses from the anterior two-thirds of the tongue.¹ While taste has been related to the trigeminal nerve, Cushing's conclusions that all of the taste fibers from the anterior two-thirds of the tongue travel in the chorda seem most acceptable (Fig. 1).¹⁻³ Other afferent fibers in the chorda carry pain and special somesthetic sensation.³ Efferent autonomic fibers innervate the submaxillary and sublingual salivary glands. Chemical solutions diffuse rapidly through the mouth,1,4-8 making localized taste-testing difficult. Another objection to the use of