PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “taste coding”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed2000

Action of calcitonin gene-related peptide (CGRP) and substance P on neurons in the insular cortex and the modulation of taste responses in the rat.

Using multibarrel electrodes, recordings were made from single neurons in the insular cortex including the cortical taste area (CTA) of urethane-anesthetized rats. The effects of an iontophoretic application of calcitonin gene-related peptide (CGRP) and substance P (SP) on the spontaneous discharges and taste responses were tested. In a total sample of neurons (mostly non-taste), CGRP affected the spontaneous discharges in 35.6% of the 571 neurons studied and SP in 38.3% of the 775 neurons studied. The effects were mostly (approximately 85-87%) facilitatory. Peptide-sensitive neurons were found at a similar frequency in all three insular areas-granular, dysgranular and agranular (areas GI, DI and AI). This is in contrast to previous reports that CGRP receptors were rich in area DI and CGRP-immunoreactive afferents numerous in area AI, but consistent with previous reports that the distribution of SP receptors and SP fibers was dense in the insular cortex. In approximately 40% of the 76 taste neurons recorded from areas GI and DI, the peptides affected the spontaneous discharges (mostly facilitated). When the taste responses were examined during application of the peptides, significant (mainly depressant) effects were seen in 61% of 18 neurons for CGRP and in 70.5% of 17 for SP. Such effects were not recognized on responses to specific taste stimuli and were not correlated with the effects on the spontaneous discharges. The findings indicate that both peptides modify taste coding in CTA neurons presynaptically and/or postsynaptically, independently of the existence of receptors on the neurons.

Animals↗
PubMed2006

The cells and logic for mammalian sour taste detection.

Mammals taste many compounds yet use a sensory palette consisting of only five basic taste modalities: sweet, bitter, sour, salty and umami (the taste of monosodium glutamate). Although this repertoire may seem modest, it provides animals with critical information about the nature and quality of food. Sour taste detection functions as an important sensory input to warn against the ingestion of acidic (for example, spoiled or unripe) food sources. We have used a combination of bioinformatics, genetic and functional studies to identify PKD2L1, a polycystic-kidney-disease-like ion channel, as a candidate mammalian sour taste sensor. In the tongue, PKD2L1 is expressed in a subset of taste receptor cells distinct from those responsible for sweet, bitter and umami taste. To examine the role of PKD2L1-expressing taste cells in vivo, we engineered mice with targeted genetic ablations of selected populations of taste receptor cells. Animals lacking PKD2L1-expressing cells are completely devoid of taste responses to sour stimuli. Notably, responses to all other tastants remained unaffected, proving that the segregation of taste qualities even extends to ionic stimuli. Our results now establish independent cellular substrates for four of the five basic taste modalities, and support a comprehensive labelled-line mode of taste coding at the periphery. Notably, PKD2L1 is also expressed in specific neurons surrounding the central canal of the spinal cord. Here we demonstrate that these PKD2L1-expressing neurons send projections to the central canal, and selectively trigger action potentials in response to decreases in extracellular pH. We propose that these cells correspond to the long-sought components of the cerebrospinal fluid chemosensory system. Taken together, our results suggest a common basis for acid sensing in disparate physiological settings.

Action Potentials↗
PubMed1994

Electrophysiological responses of Xenopus oocytes to amino acids: criteria for expression of injected mRNA coding chemoreceptors.

Responses of endogenous transporters/receptors of Xenopus oocytes to L-alanine, L-arginine, L-leucine and L-serine were investigated under voltage clamp conditions. (a) Concentration-response relations for the amino acids followed Langmuir's adsorption isotherm. (b) The neutral amino acids required Na+ to elicit the responses, whereas L-arginine did not. (c) The responses to L-alanine decreased with decreasing pH and became undetectable at pH 5.5. The present experiments supply criteria to judge if the oocytes translate exogenous mRNA coding taste or olfactory receptor proteins for the amino acids, the best characterized stimuli, especially in fishes.

Amino Acids↗
PubMedDate not supplied

Taste quality and neural coding: implications from psychophysics and neurophysiology.

Historically, taste research has often been guided by the concept that there are only four (or possibly five) basic taste qualities (sweet, sour, salty, and bitter, and possibly "umami"). All other tastes have been presumed to be combinations of these basic tastes. This psychophysical concept has been extended to electrophysiological data. That is, the neural code for each basic taste is hypothesized to be coded by a dedicated channel of neurons (the "Labeled-Line" theory); i.e., one group of neurons signals "salty" and another separate group signals "sweet." Numerous psychophysical and electrophysiological findings, however, cannot be accomodated by this quadripartite theory, which limits taste to four basic qualities and four basic neuron types. Rather, the data described in this article suggest that the range of taste is more extensive than four or five basic tastes, and that this breadth of taste quality results initially from the activation of a broad array of ion channels, receptors, and second messengers associated with taste cell membranes. These findings have implications for neural organization and provide support for the "Across-Fiber Pattern" theory in which the neural code for taste is represented by the pattern of activity across all of the neurons, i.e., neurons are not exclusively labeled for a particular sensation but cooperate with the others in the ensemble to encode taste quality.

Animals↗
PubMed2003

Taste response variability and temporal coding in the nucleus of the solitary tract of the rat.

Theories of taste coding in the brain stem have been based on the idea that taste responses are integrated over time without regard to the temporal structure of the taste-evoked spike train. In the present experiment, the reliability of response rate across stimulus repetitions and the potential contribution of temporal coding to the discrimination of taste stimuli was examined. Taste stimuli representing the four basic taste qualities were presented repeatedly, and electrophysiological responses were recorded from single cells in the nucleus of the solitary tract (NTS) of anesthetized rats. Blocks of the four tastants were repeated for as long as the cell remained isolated. Nineteen cells were recorded with between 8 and 27 repetitions of each stimulus. Response magnitude to a given tastant varied widely within some NTS cells. This impacted the determination of both the breadth of tuning and best stimulus for a given cell. The contribution of spike timing and the pattern of interspike intervals to discrimination of taste stimuli was evaluated by an information-theoretic approach based on two families of metrics. Spike timing significantly contributed to the discrimination of taste qualities in 10 of 19 (53%) cells. This contribution was especially notable during the initial 2 s of the response. Those cells that showed the most variable firing rates in response to repetition of taste stimuli tended to show the largest contribution of temporal coding. These results suggest that, in addition to response rate, the temporal parameters of responses may convey information about taste stimuli in the NTS.

Action Potentials↗
PubMed2004

Taste perception and coding in Drosophila.

BACKGROUND: Discrimination between edible and contaminated foods is crucial for the survival of animals. In Drosophila, a family of gustatory receptors (GRs) expressed in taste neurons is thought to mediate the recognition of sugars and bitter compounds, thereby controlling feeding behavior. RESULTS: We have characterized in detail the expression of eight Gr genes in the labial palps, the fly's main taste organ. These genes fall into two distinct groups: seven of them, including Gr66a, are expressed in 22 or fewer taste neurons in each labial palp. Additional experiments show that many of these genes are coexpressed in partially overlapping sets of neurons. In contrast, Gr5a, which encodes a receptor for trehalose, is expressed in a distinct and larger set of taste neurons associated with most chemosensory sensilla, including taste pegs. Mapping the axonal targets of cells expressing Gr66a and Gr5a reveals distinct projection patterns for these two groups of neurons in the brain. Moreover, tetanus toxin-mediated inactivation of Gr66a- or Gr5a-expressing cells shows that these two sets of neurons mediate distinct taste modalities-the perception of bitter (caffeine) and sweet (trehalose) taste, respectively. CONCLUSION: Discrimination between two taste modalities-sweet and bitter-requires specific sets of gustatory receptor neurons that express different Gr genes. Unlike the Drosophila olfactory system, where each neuron expresses a single olfactory receptor gene, taste neurons can express multiple receptors and do so in a complex Gr gene code that is unique for small sets of neurons.

Animals↗
PubMed1985

Gustatory responses of cortical neurons in rats. II. Information processing of taste quality.

The present report was designed to investigate neural coding of taste information in the cerebral cortical taste area of rats. The magnitude and/or type (excitatory, inhibitory, or no-response) of responses of 111 cortical neurons evoked by single concentrations of the four basic taste stimuli (sucrose, NaCl, HCl, and quinine HCl) were subjected to four types of analyses in the context of the four proposed hypotheses of taste-quality coding: across-neuron response-pattern, labeled-line, matrix-pattern, and across-region response-pattern notions (88 histologically located neurons). An across-neuron response-pattern notion assumes that taste quality is coded by differential magnitudes of response across many neurons. This theory utilizes across-neuron correlation coefficients as a metric for the evaluation of taste quality coding. Across-neuron correlations between magnitudes of responses to any pairs of the four basic taste stimuli across 111 cortical neurons were very high and were similar. However, calculations made with net responses (spontaneous rate subtracted) resulted in less positive correlations but still similar values among the various pairs of taste stimuli. This finding suggests that across-neuron response patterns of cortical neurons become less discriminating among taste qualities compared with those of the lower-order neurons. A labeled-line notion assumes that there are identifiable groups of neurons and that taste quality is coded by activity in these particular sets of neurons. Some investigators have classified taste-responsive neurons into best-stimulus categories, depending on their best sensitivity to any one of the four basic stimuli, such as sucrose-best, NaCl-best, HCl-best, and quinine-best neurons; they have suggested that taste can be classified along four qualitative dimensions that correspond to these four neuron types (i.e., four labeled lines). The present study shows that responsiveness of each of the four best-stimulus neurons had similar profiles between peripheral and cortical levels. That is, when the stimuli were arranged along the abscissa in the order of sucrose, NaCl, HCl, and quinine, there is a peak response in one place, and the responses decreased gradually from the peak. However, such response characteristics do not favor the labeled-line theory, since they can be explained in the context of the across-neuron pattern theory. A matrix-pattern notion assumes that taste quality is coded by a spatially arranged matrix pattern of activated neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2003

Peripheral coding of bitter taste in Drosophila.

Taste receptors play a crucial role in detecting the presence of bitter compounds such as alkaloids, and help to prevent the ingestion of toxic food. In Drosophila, we show for the first time that several taste sensilla on the prothoracic legs detect bitter compounds both through the activation of specific taste neurons but also through inhibition of taste neurons activated by sugars and water. Each sensillum usually houses a cluster of four taste neurons classified according to their best stimulus (S for sugar, W for Water, L1 and L2 for salts). Using a new statistical approach based on the analysis of interspike intervals, we show that bitter compounds activate the L2 cell. Bitter-activated L2 cells were excited with a latency of at least 50 ms. Their sensitivity to bitter compounds was different between sensilla, suggesting that specific receptors to bitter compounds are differentially expressed among L2 cells. When presented in mixtures, bitter compounds inhibited the responses of S and W, but not the L1 cell. The inhibition was effective even in sensilla where bitter compounds did not activate the L2 cell, indicating that bitter compounds directly interact with the S and W cells. Interestingly, this inhibition occurred with latencies similar to the excitation of bitter-activated L2 cells. It suggests that the inhibition in the W and S cells shares similar transduction pathways with the excitation in the L2 cells. Combined with molecular approaches, the results presented here should provide a physiological basis to understand how bitter compounds are detected and discriminated.

Animals↗
PubMed1971

Taste stimuli: quality coding time.

Rats conditioned to avoid drinking 300 millimolar NaCl recognized and rejected this solution within 250 to 600 milliseconds of onset of stimulus, a period containing the phasic portion of the peripheral neural response. They generalized to 500 millimolar NaCl but not to 500 millimolar sucrose. Rejection was based on quality identification neurally encoded within this brief period.

Animals↗
PubMed1991

Coding the sweet taste in the nucleus of the solitary tract: differential roles for anterior tongue and nasoincisor duct gustatory receptors in the rat.

1. A variety of chemicals that humans describe as sweet drive neurons in the nucleus of the solitary tract (NST) of the rat more vigorously when applied to the taste receptors associated with the nasoincisor ducts (NID) than when applied to taste receptors on the anterior tongue (AT). 2. The differential effects of sweet stimuli applied to the AT and NID also are evident in the set of across-neuron correlations produced by these stimuli. The psychophysical similarity among the sweet stimuli is better accounted for by responses to stimulation of the NID than by responses to stimulation of the AT (mean correlation between pairs of sweet stimuli = +0.70 for the NID, +0.44 for the AT). 3. Disaccharides or polysaccharides of glucose, i.e., maltose (0.3 M) and Polycose (0.1 M), are poor stimuli on the NID, evoking responses only 17.8 and 26.7% as great as the response elicited by sucrose (0.3 M), an optimal stimulus for this receptor subpopulation. This suggests that Polycose and maltose interact with receptor sites distinct from those with an affinity for sweet stimuli. Polycose and maltose also are ineffective stimuli on the AT, evoking responses only 11.8 and 4.9% as large as the response evoked by an optimal stimulus for this receptor subpopulation, a mixture of electrolytes (0.3 M NaCl, 0.03 M HCl, and 0.01 M quinine HCl). 4. The relative effectiveness of the sweet sugars in driving NST neurons (sucrose greater than fructose greater than glucose) correlates with their order of effectiveness in generating preference behavior in the rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1995

The perception of saltiness is eliminated by NaCl adaptation: implications for gustatory transduction and coding.

The tastes of salts to humans are complex. NaCl is the most purely salty of all salts, but even this stimulus tastes sweet at low concentrations and somewhat sour at mid-range intensities. Other salts taste significantly sour or bitter in addition to salty. Previous studies have shown that the saltiness of simple halide salts is reduced by adaptation to NaCl, suggesting that a single mechanism might be responsible for the salty taste of these stimuli. In electrophysiological studies in rodents, the response to NaCl is reduced by application to the tongue of the Na(+)-channel blocker amiloride. Organic Na+ salts are more heavily dependent on this amiloride-sensitive transduction component than NaCl, and are generally less salty and more sour. In order to investigate the relationship between NaCl saltiness and that evoked by other salts, we adapted the tongue to distilled H2O and to 0.1 M NaCl and obtained direct magnitude estimates of the taste intensity of 15 organic and inorganic Na+, Li+, K+ and Ca2+ salts, matched for total intensity. Subjects divided these magnitude estimates among the component taste qualities. Adaptation to NaCl abolished the taste of NaCl and LiCl, and eliminated the saltiness of all other salts. The magnitude estimates of the bitterness and sourness of many salts increased after NaCl adaptation. Since recent biophysical data suggest that adaptation in taste receptors may involve whole-cell mechanisms, we propose that saltiness is reduced by NaCl adaptation because it originates in the subset of taste receptors responsive to NaCl. This implies that saltiness is coded within the CNS in cells whose receptive fields include the NaCl-sensitive receptor cells and that the degree to which any salt tastes salty is determined by its ability to drive these receptors. This model proposes, for example, that KCl has a salty component because it stimulates some of the same receptor cells as NaCl, even though the transduction mechanisms for KCl are different than those engaged by NaCl. Adaptation to NaCl blocks the saltiness of KCl and other salts because they stimulate NaCl-sensitive receptor cells.

Adaptation, Psychological↗
PubMed2001

Neuronal activity in the monkey fronto-opercular and adjacent insular/prefrontal cortices during a taste discrimination GO/NOGO task: response to cues.

The neural coding of taste information in the fronto-opercular cortex (Fop) and the orbitofrontal area (OFA) was investigated by recording neural activities in monkeys performing a NaCl-water discrimination GO/NOGO task. Responses to GO (NaCl) and NOGO cues (water) were recorded from 160 neurons, of which 118 differentially responded to two cues (differential, Dif neurons), and 42 showed the same response (non-differential, ND neurons). Differential neurons included equal numbers of GO- and NOGO-dominant subtypes. Dif and ND neurons may code for different cues, e.g., taste and touch, as shown by our previous study [Jpn. J. Physiol. 44 (1994) 141]. The response latency of neurons in the exposed Fop was distributed with two modes, one at the shortest bin (100 ms) and one at the bin of 400-800 ms, but neurons in the buried Fop and OFA all had long latency. Such a difference between the two cortical groups of neurons suggests different roles in taste discrimination tasks. Most neurons did not show changes in the discharges or latency with varying concentrations of NaCl. The results indicate that neurons in the areas surveyed code for taste information differently in the task-performing state compared with the non-behaving state examined in previous studies.

Animals↗
PubMed1982

Amino acids as taste stimuli. II. Quality coding.

Two experiments were performed in rats to evaluate the relative taste qualities of 12 L-amino acids, each at a concentration which evoked half the maximum response for that chemical. The first study involved recording the activity of 40 individual chorda tympani fibers to the stimulus series. Only 34% of the evoked responses resembled the short latency phasic-tonic activity which characterizes gustatory responses to inorganic salts and acids. 32% had latencies exceeding 1 s; another 27% consisted of only a phasic burst lasting less than 1 s. The remaining 7% were inhibitory. Both long latency and purely phasic activity were stimulus selective: 61% of the former were in response to Gly or Pro while 69% of the latter were evoked by Cys-HCl, Lys-HCl or His. Response inhibition was not associated with either specific fibers or stimuli. Thus amino acids, which to humans represent a class of perceptually complex stimuli, show a corresponding complexity of evoked neural properties in the rat. The second study employed a conditioned taste aversion paradigm to assess the qualitative similarity of each amino acid to the others and to the 4 prototypical taste stimuli; NaCl, HCl, quinine-HCl and sucrose. Some amino acids showed strong generalization to a single gustatory prototype (Pro and Gly to sucrose; Cys-HCl to HCl); others generalized well to multiple prototypes (e.g. Arg to sucrose and NaCl). Several showed poor generalization to all 4 prototypical tastes, calling into question the assumption that these 4 totally encompass the gustatory domain.

Animals↗
PubMed1990

Coding channels in the taste system of the rat.

Basic taste qualities are thought to be perceived independently, yet discrete neural coding channels have not been demonstrated in the central nervous system. The response profiles of taste cells in the nucleus tractus solitarius (NTS) of the rat were categorized into four groups, and the effects of amiloride, a passive sodium channel blocker, on each were determined. NTS neurons that responded specifically to sodium chloride (NaCl) or to NaCl and sugars were suppressed by amiloride; those broadly sensitive to salts, acids, and bitter stimuli were unaffected. Moreover, the response profile evoked by NaCl lost its distinctiveness after treatment with amiloride, becoming similar to those evoked by acids and quinine. Receptors that respond to sodium must relay their information through independent coding channels to identifiable subgroups of NTS neurons, the activity of which is responsible for the perception of saltiness.

Amiloride↗
PubMed2004

Cortical spatial aspects of optical intrinsic signals in response to sucrose and NaCl stimuli.

To examine whether cortical taste neurons use spatial codes for discriminating taste information, we investigated the spatial aspects of optical intrinsic signal (OIS) responses in the gustatory insular cortex (GC) elicited by the administration of two essential tastants, sucrose and NaCl, on the tongue. OIS responses to sucrose appeared in the rostral part of the GC, whereas those to NaCl appeared in the central part of the GC. Local anesthetization of the tongue abolished OIS responses, and the administration of distilled water elicited no OIS response. Thus, taste information elicited by sucrose and NaCl from the peripheral sensory organs is segregated in the GC, suggesting that the information from two essential tastants is assembled as spatial codes in the primary cortical taste area through the process of taste quality perception.

Animals↗