Representation Of Taste Research Articles

Representation of umami taste in the human brain.

Umami taste stimuli, of which an exemplar is monosodium glutamate (MSG) and which capture what is described as the taste of protein, were shown using functional MRI (fMRI) to activate similar cortical regions of the human taste system to those activated by a prototypical taste stimulus, glucose. These taste regions included the insular/opercular cortex and the caudolateral orbitofrontal cortex. A part of the rostral anterior cingulate cortex (ACC) was also activated. When the nucleotide 0.005 M inosine 5'-monophosphate (IMP) was added to MSG (0.05 M), the blood oxygenation-level dependent (BOLD) signal in an anterior part of the orbitofrontal cortex showed supralinear additivity; this may reflect the subjective enhancement of umami taste that has been described when IMP is added to MSG. These results extend to humans previous studies in macaques showing that single neurons in these taste cortical areas can be tuned to umami stimuli.

The representation of umami taste in the human and macaque cortex

To investigate the neural encoding of glutamate (umami) taste in the primate, recordings were made from taste responsive neurons in the cortical taste areas in macaques. Most of the neurons were in the orbitofrontal cortex (secondary) taste area. First, it was shown that there is a representation of the taste of glutamate which is separate from the representation of the other prototypical tastants sweet (glucose), salt (NaCl), bitter (quinine) and sour (HCl). Second, it was shown that single neurons that had their best responses to sodium glutamate also had good responses to glutamic acid. Third, it was shown that the responses of these neurons to the nucleotide umami tastant inosine 5′-monophosphate were more correlated with their responses to monosodium glutamate than to any prototypical tastant. Fourth, concentration-response curves showed that concentrations of monosodium glutamate as low as 0.001 M were just above threshold for some of these neurons. Fifth, some neurons in the orbitofrontal region, which responded to monosodium glutamate and other food tastes, decreased their responses after feeding with monosodium glutamate to behavioural satiety, revealing a mechanism of satiety. In some cases this reduction was sensory-specific. Sixth, it was shown in psychophysical experiments in humans that the flavor of umami is strongest with a combination of corresponding taste and olfactory stimuli (e.g. monosodium glutamate and garlic odor). The hypothesis is proposed that part of the way in which glutamate works as a flavor enhancer is by acting in combination with corresponding food odors. The appropriate associations between the odor and the glutamate taste may be learned at least in part by olfactory to taste association learning in the primate orbitofrontal cortex. Seventh, in neuroimaging experiments with functional magnetic resonance imaging (fMRI) in humans, it was shown that in humans umami taste produced by monosodium glutamate or by inosine monophosphate produced activation in a region of the anterior insula which is the putative human primary taste cortex and in a part of the orbitofrontal cortex which is the putative human secondary taste cortex.

Mammalian Sweet Taste Receptors

The sense of taste provides animals with valuable information about the quality and nutritional value of food. Previously, we identified a large family of mammalian taste receptors involved in bitter taste perception (the T2Rs). We now report the characterization of mammalian sweet taste receptors. First, transgenic rescue experiments prove that the Sac locus encodes T1R3, a member of the T1R family of candidate taste receptors. Second, using a heterologous expression system, we demonstrate that T1R2 and T1R3 combine to function as a sweet receptor, recognizing sweet-tasting molecules as diverse as sucrose, saccharin, dulcin, and acesulfame-K. Finally, we present a detailed analysis of the patterns of expression of T1Rs and T2Rs, thus providing a view of the representation of sweet and bitter taste at the periphery.

Literary Daughters' Recipes

This essay examines the representations of food, cooking, and taste in the writings of Mori Mari and Kôda Aya. The critical attention these two writers have received derives mainly from their status as “literary daughters” of canonical writer-fathers. This essay, however, shifts the focus to investigate a neglected area of their writing, their evocation and exploration of female subjectivity, which is effected through a delineation of a relationship with a father in texts to do with food. Food may be represented as a token of the generosity and refinement of the parents, or as a source of domestic and/or social conflict. Cooking may be represented as a means toward aesthetic and ethical enlightenment, as a burden and chore forced on women, or as a contribution toward domestic and social harmony. The daughters' texts reveal how, through writing, they coped with the spell of the dead father. Mori Mari developed her principle of “luxurious poverty” and constructed a unique love story of a “carnivorous” girl and her father. Kôda Aya mastered fine techniques that allowed her to apply to her writing what she learned from “cooking lessons.”

Estate and empire: Sir George Cornewall's management of Moccas, Herefordshire and La Taste, Grenada, 1771–1819

Increased attention is now being paid to the relationships between cultural and material forces in the process of colonization. This paper examines the relationships developed between Britain and its colonies in the Caribbean through the landed estate, a key working and scenic landscape of late Georgian society, and the georgic discourses surrounding it. A general survey is made of colonial connections and the various media in which landed estates were represented. We argue that many connections can be found between estates in Britain and the Caribbean colonies, through material exchanges and in discourses over landscape, labour and finance. Caribbean property was accommodated by the adoption of conventional modes of representing and managing British landed estates, a process important in the assimilation of the islands as British colonies and in the integration of those with colonial interests into British élite society. But this accommodation was disrupted at certain times and places by debates over slavery in particular. In our case study of the activities of one landowner, Sir George Cornewall, we examine and compare the representation and management of La Taste, his sugar plantation in Grenada, and his Moccas estate, in Herefordshire, and we evaluate his position in British élite society.

Transient impairment of cholinergic function in the rat insular cortex disrupts the encoding of taste in conditioned taste aversion

The muscarinic antagonist scopolamine blocks conditioned taste aversion (CTA) when microinjected bilaterally into the rat insular cortex shortly before the exposure of the rat to a novel taste (the conditioned stimulus, CS) in CTA training. Scopolamine has no effect when microinjected shortly after the exposure to the novel taste or shortly before the application of the malaise-inducing agent (unconditioned stimulus, UCS). Scopolamine does not affect sensory, motor and retrieval mechanisms required for performing the CTA task, and does not block CTA when injected into another cortical area. The effect of scopolamine is independent of the taste used as CS. Furthermore, microinjection of scopolamine into the insular cortex shortly before the pre-exposure to a new taste in a latent inhibition paradigm, impairs the attenuation of CTA by that pre-exposure. Other muscarinic antagonists, pirenzepine and AF DX-116, have an effect similar to that of scopolamine. Comparison of the dose-dependency curves of the muscarinic antagonists suggests a predominant role in CTA for M2 subtype receptors. Carbachol, a muscarinic agonist, also impairs the encoding of taste in the insular cortex, but the results are confounded by the ability of that ligand to induce seizures. Our findings suggest that cholinergic neuromodulation participates in processing the CS in the gustatory cortex in CTA, either by encoding novelty at the cellular level, or by instructing the neural circuits to store the novel taste representation.

Hunger and satiety modify the responses of olfactory and visual neurons in the primate orbitofrontal cortex

1. The primate orbitofrontal cortex is the site of convergence of information from primary taste and primary olfactory cortical regions. In addition, it receives projections from temporal lobe visual areas concerned with the representation of objects such as foods. Previous work has shown that the responses of gustatory neurons in the secondary taste area within the orbitofrontal cortex are modulated by hunger and satiety, in that they stop responding to the taste of a food on which an animal has been fed to behavioral satiation, yet may continue to respond to the taste of other foods. 2. This study demonstrates a similar modulation of the responses of olfactory and visual orbitofrontal cortex neurons after feeding to satiety. Seven of nine olfactory neurons that were responsive to the odors of foods, such as blackcurrant juice, were found to decrease their responses to the odor of the satiating food in a selective and statistically significant manner. 3. It also was found for eight of nine neurons that had selective responses to the sight of food, that they demonstrated a sensory-specific reduction in their visual responses to foods after satiation. 4. The responses of orbitofrontal cortex neurons selective for foods in more than one modality also were analyzed before and after feeding to satiation. Satiety often affected the responses of these multimodal neurons across all modalities, but a sensory-specific effect was not always demonstrable for both modalities. 5. These findings show that the olfactory and visual representations of food, as well as the taste representation of food, in the primate orbitofrontal cortex are modulated by hunger. Usually a component related to sensory-specific satiety can be demonstrated. The findings link at least part of the processing of olfactory and visual information in this brain region to the control of feeding-related behavior.