Gustatory Experience Research Articles

Functional mapping of gustatory neurons in the insular cortex revealed by pERK‐immunohistochemistry and in vivo optical imaging

Neural plasticity in the gustatory area of the insular cortex (IC) plays a critical role in detecting novel taste and taste memory formation, which require extracellular signal-regulated kinase 1-2 (ERK1-2) phosphorylation. However, the distribution patterns of phosphorylated ERK1-2 (pERK) responses to gustatory stimulation remain unknown. This study examined distribution patterns of gustatory stimulation-driven pERK expression in the IC of anesthetized and alert rats. In both pentobarbital-anesthetized and alert rats, gustatory stimulation (10% sucrose) induced pERK-like immunoreactivity in pyramidal cells of all IC subdivisions: agranular (AI), dysgranular (DI), and granular IC (GI). Alert naïve rats exhibited approximately 10-fold larger number of pERK-like immunopositive (pERK-LI) cells than anesthetized naïve rats in response to sucrose application. Most pERK-LI cells were located in layers II/III but not deeper layers and almost no parvalbumin/somatostatin-immunopositive cells expressed pERK. In the AI, rostral regions exhibited more pERK-LI cells than caudal regions, whereas most pERK-LI cells existed in the DI/GI around the intersection of the rhinal fissure and middle cerebral artery (MCA), where in vivo optical imaging revealed activation during sucrose application in addition to the ventral primary and secondary somatosensory cortices. Gustatory experience affected the number of pERK-LI cells in the IC: sucrose stimulation induced more pERK-LI cells in the DI/GI of alert naïve rats than sucrose-exposed rats, which had received sucrose solution for 1 week. These results suggest that pyramidal cells in the upper layers of the gustatory region are highly susceptible to ERK1-2 phosphorylation by gustatory stimulation, which may induce neuroplastic changes in the IC.

Symposium Overview

Symposium Overview

Regional distribution of Ginkgo biloba-induced c-Fos immunoreactivity

A growing literature supports the notion that Ginkgo biloba has cognitive enhancing and anxiolytic properties; however, its effects on neuronal populations have yet to be characterized. The present study used c-Fos immunoreactivity (Fos-IR) to characterize functional activity in selected brain regions following administration of a standardized Ginkgo biloba extract. Because Ginkgo is typically consumed orally, Exp 1 sought to identify patterns of neural activity induced by oral administration. To ensure that the alterations in functional neural activity observed in Exp 1 were not simply due to novel gustatory experience, Exp 2 characterized patterns of Fos-IR following intraperitoneal administration of Ginkgo. Rats were habituated to handling and experimental conditions. In Exp 1, rats self-administered 150 mg/kg Ginkgo or vehicle alone (strawberry jam) orally. In Exp 2, rats were injected with Ginkgo (2.5 or 25 mg/kg, i.p.) or vehicle (0.3% gum Arabic). Animals were anaesthetized and perfused transcardially. Brains were sectioned, immunostained using a c-Fos antibody, then the number of labelled cells was quantified microscopically in selected brain regions. In both experiments Ginkgo increased Fos-IR in numerous brain regions including the insular cortex and amygdala. Intraperitoneal administration induced Fos-IR in some additional regions including the nucleus accumbens and dentate gyrus. Results provide important preliminary data serving to identify several candidate neural sites involved in the cognitive enhancing and anxiolytic effects of Ginkgo biloba.

The taste transduction channel TRPM5 is a locus for bitter‐sweet taste interactions

Ordinary gustatory experiences, which are usually evoked by taste mixtures, are determined by multiple interactions between different taste stimuli. The most studied model for these gustatory interactions is the suppression of the responses to sweeteners by the prototype bitter compound quinine. Here we report that TRPM5, a cation channel involved in sweet taste transduction, is inhibited by quinine (EC(50)=50 microM at -50 mV) owing to a decrease in the maximal whole-cell TRPM5 conductance and an acceleration of channel closure. Notably, quinine inhibits the gustatory responses of sweet-sensitive gustatory nerves in wild-type (EC(50)= approximately 1.6 mM) but not in Trpm5 knockout mice. Quinine induces a dose- and time-dependent inhibition of TRPM5-dependent responses of single sweet-sensitive fibers to sucrose, according to the restricted diffusion of the drug into the taste tissue. Quinidine, the stereoisomer of quinine, has similar effects on TRPM5 currents and on sweet-induced gustatory responses. In contrast, the chemically unrelated bitter compound denatonium benzoate has an approximately 100-fold weaker effect on TRPM5 currents and, accordingly, at 10 mM it does not alter gustatory responses to sucrose. The inhibition of TRPM5 by bitter compounds constitutes the molecular basis of a novel mechanism of taste interactions, whereby the bitter tastant inhibits directly the sweet transduction pathway.

Christina Rossetti: Illness and Ideology

Doubtless the most familiar references to illness in the poetry of Christina Rossetti appear in Goblin Market after Lizzie's sister Laura has banqueted on the sumptuous fruits proffered by the demonic Goblin men (the only males, one recalls, who actually appear in the poem). Ecstatic for the moment, Laura returns to the maidens' garden cottage promising to bring sister plums ... / Fresh on their mother twigs and cherries worth getting. She describes feast in detail: You cannot think what figs My teeth met in, What melons icy-cold Piled on a dish of gold Too huge for me to hold, What peaches with a velvet nap, Pellucid grapes without one seed: Odorous indeed must be the mead Whereon they grow, and pure the wave they drink With lilies at the brink, And sugar-sweet their sap. (1) Such delicate fruits would, in our own age, appear to be a tonic for any illness, but Laura's allusion to iconic lilies, in this context, suggests the delusory quality of gustatory experience: soon, in fact, her tree of life drooped from the root (l. 260). She is overwhelmed by her heart's sore ache and an unquenchable yearning (ll. 261, 266). She sickens, says the narrative voice: Her hair grew thin and gray; She dwindled, as the fair full moon doth mm To swift decay and burn Her fire away. (ll. 277-280) With sunk eyes and faded mouth (l. 288), final stages of deterioration begin. In a both literally and figuratively pivotal passage that appears about midway through the poem, when Laura, dwindling / Seemed knocking at Death's door (ll. 320-321), sister Lizzie is reminded of Jeanie in grave, Who should been a bride; But who for brides hope to Fell sick and died In prime. (ll. 312-316) Eventually, of course, Lizzie braves the Goblin glen and the vicious assaults of the demons themselves, to return dripping with fruit juices which Laura sucks from body and by which she is miraculously saved, indeed resurrected: Life out of death (l. 524), we are told, was their effect. As with so many modern vaccines, the antidote to the disease--presumably unavailable to Jeanie--is derived from its source. Before leaving this passage about Jeanie, crucial to a number of the poem's ideological resonances, we should observe its striking statement of causality and its equally startling collocation of associations: here brides hope to have are implicitly identified with Laura's powerfully sensual experience of the Goblin fruit, defining temptation by the Goblin men as a sexual one. Moreover, the premature and illicit experience of such joys causes Jeanie to become a fallen woman (recall that she fell sick). This association becomes explicit with Rossetti's choice of the word gay to describe her: the term in the mid-Victorian lexicon commonly referred to prostitutes. (2) In this central passage from Rossetti's title poem in debut volume, an equation is thus set up between the indulgence of female sexual desire and sickness unto death. In cultural context, this poem can be read as a monitory exemplum and thus an extreme instance of Victorian sexual repression: it reflects a profound fear of female sexuality and its potential consequences. (3) The fear and sublimation of female sexual desire and insistence upon the dangerous, if not fatal, effects of its indulgence emerges often--metaphorically, if not literally--in much of Rossetti's poetry. We witness it not only in Goblin Market: it permeates works, (4) prose as well as poetry, from the 1850s--one immediately thinks of juvenile prose tale, Maude, as well as poems such as The Convent Threshold and An Apple-Gathering, for instance--to last major poems, including the justly admired Monna Innominata sonnet of sonnets. That fear, I will eventually argue, also played a powerful role in Rossetti's own life, from the emergence of passionate religiosity at about the same time as serious adolescent illness--to ultimate rejection of two marriage proposals, and the arguments against marriage made in works of devotional prose. …

Word — Gustatory Synesthesia: A Case Study

A case study of a rare form of synesthesia is presented, where specific words act as the inducer, and gustatory sensations function as the concurrent. The female participant (TD) was twice presented with a list of 806 English words and 222 grammatically correct non-words (with 3 months between presentations). For each presentation, TD was asked to provide: a subjective description of the gustatory experience (if any) associated with each stimulus; a rating (from 0 to 10) of the intensity of the gustatory experience; and an indication (yes/no) if the experience was aversive. TD's responses across the two presentations were quantified, and comparisons are provided. In addition, TD's ability to create and recall novel word-taste associations was compared to that demonstrated by a sample of ten age-matched non-synesthete females. TD's synesthetic experiences were found to be highly consistent, more common in English words than non-words, and rarely aversive. Although TD was superior to control participants in remembering novel word-taste associations, her reported experiences cannot be wholly explained by either an exceptional non-synesthetic learning of taste-word associations over time, or a clear response to phonemes, rather than whole words. These conclusions are compared to the five other published reports of word-gustatory synesthesia, and directions for future research are discussed.

The Cardiff Anomalous Perceptions Scale (CAPS): A New Validated Measure of Anomalous Perceptual Experience

The study describes the Cardiff Anomalous Perceptions Scale (CAPS), a new validated measure of perceptual anomalies. The 32-item CAPS measure is a reliable, self-report scale, which uses neutral language, demonstrates high content validity, and includes subscales that measure distress, intrusiveness, and frequency of anomalous experience. The CAPS was completed by a general population sample of 336 participants and 20 psychotic inpatients. Approximately 11% of the general population sample scored above the mean of the psychotic patient sample, although, as a group, psychotic inpatients scored significantly more than the general population on all CAPS subscales. A principal components analysis of the general population data revealed 3 components: "clinical psychosis" (largely Schneiderian first-rank symptoms), "temporal lobe disturbance" (largely related to temporal lobe epilepsy and related seizure-like disturbances) and "chemosensation" (largely olfactory and gustatory experiences), suggesting that there are multiple contributory factors underlying anomalous perceptual experience and the "psychosis continuum."

Repeated exposures to gustatory stimuli produce habituation or positive contrast effects in perinatal rats.

Adult rats exhibit a decrease in consummatory responses following repeated presentations of a taste (habituation) and an increase in consummatory responses if they experience an upward shift in the magnitude or intensity of a gustatory stimulus (e.g., sucrose or saccharin). These responses do not represent a direct sensorimotor reaction to a gustatory cue, but rather reflect a change in responding based on the memory of a previous taste. Here, we sought to determine if fetal rats could (like adults) adjust their orofacial motor responses based on a memory of recent gustatory experience. Embryonic Day 18 (E18) or Day 19 (E19) rat fetuses received oral lavage with either 0.15 or 0.30% saccharin (SAC). Subsequently, observations of orofacial movements (mouthing and licking) following oral lavage with 0.30% SAC were made 50 min later, 24 hr later, or on postnatal Day 3 (P3). Thus, some animals were in a "shifted" condition in which they first experienced a relatively low concentration of SAC and then a higher one while control rats ("nonshifted") received 0.30% SAC during both taste exposures. Fetuses exhibited evidence of both habituation (with repeated presentation of the 0.30% SAC) and positive contrast effects (PCEs) (following an upward shift in SAC concentration) when retested 50 min after their first exposure to SAC on E19. However, these animals did not exhibit PCEs 24 hr later or 5 days later (on P3). Contrast effects were not observed when the initial SAC exposure was on E18, and habituation responses were variable depending on the time interval between the taste presentations to these animals. Rats with a 5- to 6-day latency between the two taste presentations showed neither PCEs nor habituation. Our data indicate that PCEs and habituation effects emerge at different ages, and their demonstration is dependent upon the latency between the taste presentations.

Newborn rats' first suckling experience: Taste differentiation and suckling plasticity

The present study examined responsiveness of newborn rats to a surrogate nipple providing fluids with basic tastes (sweet, sour, bitter and salty) and assessed the effects of this first gustatory experience on subsequent responding to the nipple itself (empty nipple) or the nipple providing water. Responsiveness (attachment to and ingestion from a surrogate nipple providing saccharin, saline, quinine or ammonium chloride) was compared with that toward a nipple providing water. Compared to water, saline and quinine significantly reduced attachment to and ingestion from the nipple, while saccharin and milk significantly increased attachment behavior. Ammonium chloride increased attachment but not ingestive behavior. Suckling experience with saline, quinine and ammonium chloride attenuated both attachment and ingestive behaviors when subjects were tested 1 h later with an empty surrogate nipple or a nipple providing water. Experience with saccharin and milk (but not water) increased both measures. The data suggest that in newborn rats, as early as a few hours after birth, mechanisms of gustatory detection have control over suckling behavior. Initial experience with the tastants available from the nipple in the first suckling episode may alter further responsiveness to the nipple itself, mediated perhaps by mechanisms of appetitive and aversive conditioning.

Fire Within the Eye By David A. Park (review)

oping the atomic force microscope. Moreover, a number of investigators have been able to move atoms from place to place using the scanning tunneling microscope, one of the most notable examples being Donald Eigler's positioning of 35 xenon atoms on a nickel surface so as to spell "IBM," his employer at the IBM Research Laboratory in Almadén, California. On a personal note, I began with the history of atomism as an academic exercise in college and am now using the atomic force microscope for biomedical investigations . Perhaps the history of the idea never left me. I recommend this book most enthusiastically. This is a fascinating and eminently readable account of modern atomism, the indivisible becoming divisible and the invisible becoming visible. The relationship among science, theology, and philosophy is a fascinating tale of humans , their humanity, and their unquenchable interest in discovery. Morton F. Arnsdorf, M.D. University of Chicago Fire Within the Eye. By David A. Park. Princeton: Princeton UP, 1997. Pp. 550. $29.95. Imagine for a moment an elaborate dinner party, in which the host has taken great pains to prepare an evening that will be an enjoyable and memorable experience for all who attend. The guests are gracefully attired. The venue is carefully chosen and richly decorated. The meal progresses languidly, over the entire evening . Each course is meticulously prepared and artfully presented. Only the freshest ingredients are used, only the finest wines are served. The guest who has come mentally prepared for this gustatory experience savors every delicious mouthful from the aperitif to the dessert. This is not the event for someone in a hurry to finish dinner and get home. For the reader who seeks a detailed history of research in the visual sciences, author David Park in Fire Within the Eye is host to an historical feast. Beginning with the earliest accounts of philosophical theories on light and vision, he meticulously recounts the progression of electromagnetic science. He begins with a discussion of the influence of the Greeks and Romans, from there moves eastward toward Egypt, and then to France and Italy. Eventually his discussion travels to the modern scientific era of Germany, Great Britain, and the United States. Throughout his presentation, Park reminds his reader of the prevailing religious, cultural, and philosophical milieu in which various researchers were working. He thereby gives his reader a sociopolitical context in which to view the progression and maturation of vision and light science. HORS D OEUVRES AND APERITIF The experience begins shortly after the reader arrives for Park's feast. The guest immediately notices the environment in which he has arrived: he observes the art on the walls, the weave of the carpet, the pattern of the upholstery. Other guests arrive, they meet and mingle; conversations are begun and ideas are introduced. 444 I Book Reviews Park introduces his reader to some of the earliest philosopher/scientists investigating light and vision, as well as to the ideological climate of the time. He begins in the middle of the 5th century BC, when the concepts of light, space, matter, and creation were inextricably linked. Philosophers such as Empedocles, Leucippus, Democratus, and Aristotle successively wrestled with theories and definitions of atoms and space, and the relationship between them and God. Empedocles (c. 495-435 bc) believed that matter and light were eternal, and that only their forms were subject to change. From this, Leucippus (c. 450 bc) conceived of matter as formed images made up of atoms that move at very high speeds. Yet, these atoms maintain their general position such that what is seen as an apparently stationary object is in reality rapidly changing. Aristotle (384-322 bc) gave an early definition of light as an entity that activates all substances. His limitation, however, was his inability to conceive of light as having the speed necessary to explain the rapidity with which one sees distant targets. None of these early thinkers, however, delved into the physiology of vision. It was Galen (c. 130-200) who studied the anatomy of the eye and suggested that it was the lens that was the sensory organ of vision. He believed that the retina and optic nerve were...

Prevalence of Auditory, Olfactory, and Gustatory Experiences in Home Dreams

Although numerous studies have investigated the content of laboratory and home dream reports, surprisingly little is known about the prevalence of various sensory modes in dreams. 49 men and 115 women completed a battery of questionnaires and kept a home dream diary for two to three consecutive weeks. Retrospective responses to the questionnaire indicate that approximately 33% of men and 40% of women recalled having experienced sensations of smell or taste in their dreams. A total of 3372 dream reports were collected and scored for unambiguous references to auditory, olfactory, and gustatory experiences. Auditory experiences were reported in approximately 53% of all dream reports. Olfactory and gustatory sensations occurred in approximately 1% of all dream reports. A significantly greater percentage of women than men reported one or more dreams containing references to olfactory sensations. The results lend support to previous studies which have shown that a variety of sensory experiences, although relatively rare, can occur in dreams.

Immunomodulation by behavioural conditioning

The contemporary surge in studies of behaviourally conditioned immunomodulation following Ader and Cohen (1975) was preceded by Pavlovian conditioning conducted in the Soviet Union during the 1920s and 1950s. Data from these studies provided a tenable hypothesis for immunomodification using classical conditioning processes. In particular a variant of Pavlovian conditioning, the conditioned taste aversion (CTA) paradigm, has proved very robust; here a novel gustatory experience (CS) is paired with an aversive physiological event (UCS) and subsequent gustatory avoidance of the CS alone is measured. Similar procedures have also been successfully applied to the conditioned alteration of cellular immune responses. Studies demonstrating behaviourally conditioned effects on the immune system are reviewed. More recently, conditioned immunoenhancement studies have demonstrated that taste aversion can induce a conditioned increase in the helper: suppressor T cell subset ratio in rats, and a depressed DTH response in mice. Mediating mechanisms for the conditioned effects are examined, in particular the roles of adrenocorticotropin (ACTH) and beta-endorphin (BEP), and the routes of communication between the CNS and immune system. Clinical applications of immunomodification may also be demonstrated by the potential therapeutic efficacy of both conditioned immunosuppression and immunoenhancement.

Taste bud development in chickens (Gallus gallus domesticus).

Oral epithelium in the anterior mandibular glands region was examined in embryonic, hatchling, and mature chickens to establish the timing of morphologic events during taste bud ontogeny. Hematoxylin-and-eosin-stained sections (10 microns) from 27 Anak (broiler breed) chickens were examined serially, and buds were quantified at 16-20 days of incubation (E) and, posthatch days 1 and 50-60. Taste buds were first recognized at the beginning of E17 as small clusters of cells in the basal epithelium. Only spherical-shaped buds were observed on E17 and E18, and these spherical clusters never penetrated to the surface of the stratified epithelial layer. E19 marked a transitional stage when mature bud features began to emerge: the buds assumed a more elongate shape, several kinds of cells comprising the bud were distinguishable and the first taste pores were observed. During the ensuing embryonic days, buds continued to elongate commensurate with the deepening oral epithelium and by hatching virtually all buds opened to the oral cavity. No marked morphological changes in taste bud structure were observed on the day of hatching and at 50-60 days posthatching. Taste bud numbers increased dramatically during E17 and E18, peaked on E19, and remained relatively constant thereafter. It is concluded that the morphological sequence of taste bud development in chickens is similar to that in mammals. The timing of bud ontogeny, though initiated only during the third trimester in ovo, essentially is completed by hatching, thus providing the precocial hatchling with the sensory apparatus essential for gustatory experience.

Threshold hypothermia disrupting acquisition of conditioned taste aversion and attenuation of neophobia in rats

As shown by earlier research, hypothermia elicited after taste exposure disrupts neither the gustatory trace nor its association with poisoning (conditioned taste aversion, CTA), but prevents positive labeling of the gustatory trace in the absence of poisoning (attenuation of neophobia, AN). On the other hand, no CTA is formed when both the taste stimulus and poisoning are administered to hypothermic rats, probably because the gustatory experience is not recorded in the short-term memory. The minimum hypothermia causing the above effects was established. In Experiment 1, water-deprived rats were cooled in an ice bath to colonic temperatures between 24 and 36°C, force-fed with 0.1% saccharin (CS), and poisoned (US) 30 min later with 0.15 M LiCl (2% body weight). Spontaneous saccharin intake tested 2 days later was considerably decreased in animals exposed to saccharin at temperatures above 32°C, but CTA was absent in rats receiving the CS at body temperatures lower than 32°C. In Experiment 2, water-deprived rats were offered a novel flavor (apple juice), eliciting a marked neophobic reaction, and cooled immediately afterwards to colonic temperatures between 20 to 34°C. Two days later, apple juice intake was almost doubled in control rats and in rats cooled to 34°C, but no AN was seen in animals cooled to or below 29°C. It is concluded that formation of the gustatory trace and its positive labeling in absence of poisoning are disrupted at body temperatures interfering with the acquisition of other instrumental reactions.

Developmental changes in neurophysiological taste response from the medulla in sheep

To determine whether functional characteristics of the taste system change during development, electrophysiological taste responses were recorded from neurons in the solitary complex (nucleus and tractus solitarius) in the medulla of fetal, newborn and adult sheep. Taste stimuli included NH 4Cl, KCl, NaCl, LiCl, citric acid, and HCl, applied to the anterior tongue. Fetal neurons at all ages (84–137 days of gestation) responded to stimulation of the tongue with NH 4Cl and KCl, but responses to NaCl and LiCl were only obtained in older fetuses (after 114 days of gestation), lambs and adults. Responses to citric were obtained at all ages; however, HCl responses were only infrequently obtained in young fetuses. Other developmental changes included a progressive decrease in latency of the responses to NH 4Cl, KCl, citric acid and HCl, and an increase in the duration of the neural response discharge as a function of gestational age. Since taste buds do not acquire the structural characteristics of the adult until the last third of gestation (∼ 100–147 days), these functional changes in taste response characteristics take place concurrently with structural development. Mammalian fetuses swallow amniotic fluid in utero, and therefore, the fetal taste system is stimulated during structural and functional development. Thus, there is an opportunity for fetal gustatory experience to influence the developing taste system.

Acceptance of novel flavours is increased after early experience of diverse tastes

WE believe that the more an animal experiences diversity of flavours at one time the more it will accept novel flavours later. Thus, rats given several distinctive flavours early in life would be more likely to accept an unfamiliar flavour later than would rats whose early gustatory experiences have been less varied. This hypothesis has had some empirical support in the literature. Kuo1, for example, mentions pilot research suggesting that cats, dogs and mynah birds raised on restricted diets for extended periods avoided new food, while others of their kind reared on varied diets ate novel foods readily. We have now found a similar effect with rats using flavoured solutions rather than solid foods.

Functional decortication in the CS-US interval decrease efficiency of taste aversive learning

Conditioned taste aversion was studied in 160 rats with the cortical spreading depression (CSD) technique. Water-deprived animals had 15-min access to water on the familiarization Days 1 and 2. On Day 3 they were offered saccharin (0.1%, CS) followed after 30–300 min by intraperitoneal LiCI injection (0.14 M, 2% body wt, US). Saccharin intake on Day 4 increased proportionally to the duration of CS-US interval from 40% (30 min) to 86% (240 min) and 103% (300 min) of Day 3 consumption. Bilateral CSD evoked 15 min after CS termination and maintained during the rest of the CS-US interval impaired the taste aversion conditioning with 120- and 180-min delays (85% and 89%) but not with 30- and 60-min delays (32% and 50%). Gustatory experience acquired during unilateral CSD on Day 3 yielded strong conditioned aversion with 20- and 60-min CS-US delays (40% and 43%). When bilateral CSD was induced 10 min after hemidecorticate exposure to saccharin, significant aversion was found with the 20- and 40-min delays (38% and 53%) but not with 50- and 60-min delays (95% and 87%). It is concluded that CSD interferes with the short-term storage of the gustatory information acquired with the intact brain.