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Results for “gustatory cortex”

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At least 19 recordsLinked to original sources

PubMed1996

Correlated discharges of two neurons in rat gustatory cortex during gustatory stimulation.

During application of tastants into the oral cavity correlated activities were observed in 27 of 64 neuron pairs recorded simultaneously in the gustatory cortex of anesthetized rats. The mean frequency of correlated discharges as assessed from the size of the peak appearing in the cross-correlogram was lower (0.2-0.33 spikes/s) and the mean width of the peaks was wider (8 ms) as compared to those reported in the gustatory relay stations in the brainstem. In a few cases troughs were formed or peaks appeared with a long delay.

Animals↗

PubMed2006

A 3 T event-related functional magnetic resonance imaging (fMRI) study of primary and secondary gustatory cortex localization using natural tastants.

INTRODUCTION: It is known that taste is centrally represented in the insula, frontal and parietal operculum, as well as in the orbitofrontal cortex (secondary gustatory cortex). In functional MRI (fMRI) experiments activation in the insula has been confirmed, but activation in the orbitofrontal cortex is only infrequently found, especially at higher field strengths (3 T). Due to large susceptibility artefacts, the orbitofrontal cortex is a difficult region to examine with fMRI. Our aim was to localize taste in the human cortex at 3 T, specifically in the orbitofrontal cortex as well as in the primary gustatory cortex. METHODS: Event-related fMRI was performed at 3 T in seven healthy volunteers. Taste stimuli consisted of lemon juice and chocolate. To visualize activation in the orbitofrontal cortex a dedicated 3D SENSE EPI fMRI sequence was used, in addition to a 2D SENSE EPI fMRI sequence for imaging the entire brain. Data were analyzed using a perception-based model. RESULTS: The dedicated 3D SENSE EPI sequence successfully reduced susceptibility artefacts in the orbitofrontal area. Significant taste-related activation was found in the orbitofrontal and insular cortices. CONCLUSION: fMRI of the orbitofrontal cortex is feasible at 3 T, using a dedicated sequence. Our results corroborate findings from previous studies.

Adult↗

PubMed1988

The responsiveness of neurones in the frontal opercular gustatory cortex of the macaque monkey is independent of hunger.

1. In order to determine whether the responsiveness of neurones in the primary gustatory cortex is influenced by hunger, the activity of neurones in the gustatory cortex in the frontal operculum was recorded while macaque monkeys (Macaca fascicularis) were fed to satiety. The responses of single neurones in the gustatory cortex to the prototypical taste stimuli glucose, NaCl, HCl and quinine hydrochloride, and to fruit juice, were measured before, while, and after the monkey was fed to satiety with glucose or fruit juice. 2. While behaviour turned from avid acceptance to active rejection upon repletion, the responsiveness of the neurones to the stimulus array, including the satiating solution, was unmodified. 3. It is concluded that in the gustatory cortex in the frontal operculum, neuronal responses to gustatory stimuli are not influenced by the normal transition from hunger to satiety. This is in contrast to the responses of a population of neurones recorded in the hypothalamus, which only occur to the taste of food when the monkey is hungry. Thus the neurones in the primary gustatory cortex are involved in a motivation-independent analysis of gustatory stimuli, whereas the hypothalamic neurones may be more closely related to the influence of motivational state on behavioural responsiveness to gustatory stimuli.

Action Potentials↗

PubMed1993

Taste memory: the role of protein synthesis in gustatory cortex.

Application of the protein synthesis inhibitor anisomycin to the rat gustatory cortex before and during training impairs conditioned taste aversion (CTA) to saccharin. No behavioral impairment is observed if the inhibitor is applied to an adjacent cortical area or to one cortical hemisphere only. The consumption of saccharin and of total fluid, as well as behavioral recognition of saccharin, is not affected. Preexposure of rats to saccharin several days before training markedly inhibits CTA to that taste. Injection of anisomycin to the gustatory cortex immediately prior to the preexposure period attenuates the latent inhibition. These results suggest that protein synthesis in the gustatory cortex is required for normal acquisition of the memory of taste.

Animals↗

PubMed1988

The responsiveness of neurons in the insular gustatory cortex of the macaque monkey is independent of hunger.

(1) In order to determine whether the responsiveness of neurons in the insular gustatory cortex is influenced by hunger, neuronal activity was analysed in it while macaque monkeys (Macaca fascicularis) were fed to satiety. The responses of single neurons in the insular gustatory cortex to the protypical taste stimuli glucose, NaCl, HCl and quinine HCl, and to fruit juice, were measured before, while, and after the monkey was fed to satiety with glucose or fruit juice. (2) While behavior turned from avid acceptance to active rejection upon repletion, the responsiveness of the neurons to the stimulus array, including the satiating solution, was unmodified. (3) It is concluded that in the insular gustatory cortex, neuronal responses to gustatory stimuli are not influenced by the normal transition from hunger to satiety. This is in contrast to the responses of a population of neurons recorded in the hypothalamus, which only respond to the taste of food when the monkey is hungry. Thus the neurons in the insular gustatory cortex are involved in a motivation-independent analysis of gustatory stimuli, whereas the hypothalamic neurons may be more closely related to the influence of motivational state on behavioral responsiveness to gustatory stimuli.

Amygdala↗

PubMed2002

Taste-specific neuronal ensembles in the gustatory cortex of awake rats.

In gustatory cortex, single-neuron activity reflects the multimodal processing of taste stimuli. Little is known, however, about the interactions between gustatory cortical (GC) neurons during tastant processing. Here, these interactions were characterized. It was found that 36% (85 of 237) of neuron pairs, including many (61%) in which one or both single units were not taste specific, produced significant cross-correlations (CCs) to a subset of tastants across a hundreds of milliseconds timescale. Significant CCs arose from the coupling between the firing rates of neurons as those rates changed through time. Such coupling significantly increased the amount of tastant-specific information contained in ensembles. These data suggest that taste-specific GC assemblies may transiently form and coevolve on a behaviorally appropriate timescale, contributing to rats' ability to discriminate tastants.

Action Potentials↗

PubMed1995

Aversive taste stimuli facilitate extracellular acetylcholine release in the insular gustatory cortex of the rat: a microdialysis study.

The release of extracellular acetylcholine (ACh) in the insular gustatory cortex of conscious rats during taste stimulation was measured using the microdialysis technique. The mean basal release of ACh before stimulation was 273 +/- 21 fmol/10 microliters (mean +/- S.E.M., n = 25). Intraorally applied taste stimuli or distilled water significantly increased the release of ACh. Among them, infusion of 0.001 M quinine HCl produced a marked increase in the release of ACh up to 355% of baseline levels. Infusion of 0.01 M saccharin to the subjects that had acquired an aversion to this taste also caused a prominent increase in ACh up to 343% of basal levels. In contrast, saccharin infusion to the naive subjects moderately increased ACh up to 243% of baseline. Water infusion resulted in the smallest increase in ACh up to 175% of baseline. Although intraoral infusions of quinine or distilled water caused a significant increase in ACh in the parietal cortex, the magnitude of increased ACh was smaller than that in the gustatory cortex. These results suggest that ACh release in the insular gustatory cortex is related to behavioral expression to aversive taste stimuli.

Acetylcholine↗

PubMed1994

Classification of inhibitory responses of the hamster gustatory cortex.

Neuronal activity was recorded in the gustatory cortex of the golden Syrian hamster in response to application of taste stimuli to the anterior tongue. Two classes of inhibitory responses were detected: (1) a decrease in activity in response to application of individual taste stimuli: and (2) a decrease in activity in response to application of a mixture of taste stimuli but not in response to application of individual taste stimuli.

Animals↗

PubMed2001

Three-dimensional estimation of the distribution and size of putative functional units in rat gustatory cortex as assessed from the inter-neuronal distance between two neurons with correlative activity.

Two neurons recorded simultaneously in rat gustatory cortex often show, when the oral mucosa is stimulated with effective taste solutions, correlative activities (CAs), which can be quantified with a cross-correlation technique. It has been suggested that the CAs are involved in taste quality discrimination and the neuron pairs with CA (CA pairs) may function as a unit (putative functional unit). The present experiment was undertaken (1) to determine the three-dimensional size of putative functional units in rat gustatory cortex on the basis of the interneuronal distance (IND) in individual CA pairs, and (2) to examine to what extent the CA is related to the intrapair similarity in taste responses. The findings were as follows: (1) The CAs occurred in 30 out of 55 pairs with INDs < or =270 microm and often at INDs <100 microm. (2) The numbers of putative functional units were calculated tentatively by using the longest or the mean INDs; at least 200 or over 4,000 units, respectively. (3) In the CA pairs, the "best taste" was identical (homo-type) in many pairs, the "taste profiles" were often similar, and the temporal courses of taste responses resembled each other in more than one half of the pairs. A possible role of hetero-type pairs was discussed. (4) In a small number of cases, troughs were observed in the CCs, suggesting the involvement of local inhibitory neurons. In conclusion we point out that nearby neurons are prone to CA, if (1) their best tastes are identical, (2) their taste profiles are similar, and (3) the temporal patterns of taste response resemble each other.

Action Potentials↗

PubMed2005

Laterality of human primary gustatory cortex studied by MEG.

We examined the laterality of the human gustatory neural pathway by measuring gustatory-evoked magnetic fields (GEMfs) and demonstrating the activation of the human primary gustatory cortex (PGC). In patients whose chorda tympani nerve had been severed unilaterally on the right side, we stimulated the normal side (i.e., left side) of the chorda tympani nerve with NaCl solution using a device developed for measuring GEMfs. We used the whole-head magnetoencephalography system for recording GEMfs and analyzed the frequency and latency of PGC activation in each hemisphere. "The transitional cortex between the insula and the parietal operculum" was identified as PGC with the base of the central sulcus in this experiment. Significant difference was found in frequencies among bilateral, only-ipsilateral, and only-contralateral responses by the Friedman test (P < 0.05), and more frequent bilateral responses were observed than only-ipsilateral (P < 0.05) or only-contralateral responses (P < 0.01) by the multiple comparison tests. In the bilateral responses, the averaged activation latencies of the transitional cortex between the insula and the parietal operculum were not significantly different in both hemispheres. These results suggest that unilateral gustatory stimulation will activate the transitional cortex between the insula and the parietal operculum bilaterally in humans.

Adult↗

PubMed1998

Tetrodotoxin inactivation of the gustatory cortex disrupts the effect of the N-methyl-D-aspartate antagonist ketamine on latent inhibition of conditioned taste aversion in rats.

The effect of the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist ketamine on latent inhibition of taste aversion learning was studied in rats. Systemic injections of ketamine (50 mg/kg) applied after each of three preexposures to sodium saccharin (0.1%) disrupted the latent inhibition effect. The blockade was not due to aversive properties of ketamine, because three saccharin-ketamine pairings did not produce saccharin aversion. Moreover, the ketamine-induced blockade of latent inhibition was disrupted by tetrodotoxin injections (10 ng/microl)-induced reversible inactivation of gustatory cortex, applied after each preexposure. A specific gustatory cortex mediation of the ketamine effect is discussed.

Animals↗

PubMed2006

Rapid taste responses in the gustatory cortex during licking.

Rapid tastant detection is necessary to prevent the ingestion of potentially poisonous compounds. Behavioral studies have shown that rats can identify tastants in approximately 200 ms, although the electrophysiological correlates for fast tastant detection have not been identified. For this reason, we investigated whether neurons in the primary gustatory cortex (GC), a cortical area necessary for tastant identification and discrimination, contain sufficient information in a single lick cycle, or approximately 150 ms, to distinguish between tastants at different concentrations. This was achieved by recording neural activity in GC while rats licked four times without a liquid reward, and then, on the fifth lick, received a tastant (FR5 schedule). We found that 34% (61 of 178) of GC units were chemosensitive. The remaining neurons were activated during some phase of the licking cycle, discriminated between reinforced and unreinforced licks, or processed task-related information. Chemosensory neurons exhibited a latency of 70-120 ms depending on concentration, and a temporally precise phasic response that returned to baseline in tens of milliseconds. Tastant-responsive neurons were broadly tuned and responded to increasing tastant concentrations by either increasing or decreasing their firing rates. In addition, some responses were only evoked at intermediate tastant concentrations. In summary, these results suggest that the gustatory cortex is capable of processing multimodal information on a rapid timescale and provide the physiological basis by which animals may discriminate between tastants during a single lick cycle.

Animals↗

PubMed2006

Reproducing bursting interspike interval statistics of the gustatory cortex.

Cortical neurons in vivo generate highly irregular spike sequences. Recently, it was experimentally found that the local variation of interspike intervals, LV, is nearly constant for every spike sequence for the same neurons. On the contrary, the coefficient of variation, CV, varies over different spike sequences. Here, we first show that these characteristic features are also applicable in bursting spike sequences that are obtained from the rat gustatory cortex. Next, we show that the conventional leaky integrate-and-fire model does not fully account for reproducing these statistical features in data of real bursting spike sequences. We resolve this difficulty by proposing an alternative neuron model which is a reduction of the bursting neuron model involving the persistent sodium current. Our study implies that (1) the characteristic features of CV and LV are the results of the endogenous bursting and (2) the bursting behavior in the gustatory cortex is caused mainly by the persistent sodium current.

Animals↗

PubMed2004

Neural signature of taste familiarity in the gustatory cortex of the freely behaving rat.

Ample data indicate that the gustatory cortex (GC) subserves the processing, encoding, and storage of taste information. To further elucidate the neural processes involved, we recorded multi-unit activity in the GC of the freely behaving rat as it became familiar with a novel tastant. Exposure to the tastant was performed over three 40- to 50-min sessions, 24 h apart. In each session, the tastant was presented repeatedly, 1 s at a time, with 10- to 12-s inter-trial intervals. The neural response to the tastant typically lasted 7 s. Our results show that the average neuronal response to the tastant increased as this tastant became familiar, but this increase was detected only during the last 5 s of the response. The increased response was not generalized to another tastant. Furthermore, our analysis suggests that specific neuronal populations subserve the processing of familiarity of specific tastants. The signature of familiarity was not detected in the course of the familiarization session, but only on the subsequent day, suggesting that its development involves slow post-acquisition processes. Our data are in line with the notion that GC neurons process multiple taste attributes, familiarity included, during different temporal phases of their response. The data also suggest that by default the brain considers a taste stimulus as novel, unless proven otherwise.

Animals↗

PubMed2006

Effects of acetylcholine on coding of taste information in the primary gustatory cortex in rats.

Acetylcholine (ACh) receptors are widely distributed throughout the cerebral cortex in rats. Recently, cholinergic innervation of the gustatory cortex (GC) was reported to be involved in certain taste learning in rats. Here, the effects of iontophoretic application of ACh on the response properties of GC neurons were studied in urethane-anesthetized rats. ACh affected spontaneous discharges in a small fraction of taste neurons (11 of 86 neurons tested), but influenced taste responses in 27 of 43 neurons tested. No correlations with ACh susceptibility were noted for spontaneous discharges and taste responses. Among the 27 neurons, ACh facilitated taste responses in 13, inhibited taste responses in 13 and either facilitated or inhibited taste responses depending on the stimuli in 1. Furthermore, ACh affected the responses to best stimuli that produced the largest responses among four basic tastants (best responses) in 7 of 27 taste neurons, to non-best responses in 9, and to both best and non-best responses in 11. ACh mostly inhibited the best responses (13 of 18 neurons). Thus, ACh often decreased the response selectivity to the four basic tastants and changed the response profile. Atropine, a general antagonist of muscarinic receptors, antagonized ACh actions on taste responses or displayed the opposite effects on taste responses to ACh actions in two-thirds of the neurons tested. These findings indicate that ACh mostly modulates taste responses through muscarinic receptors, and suggest that ACh shifts the state of the neuron network in the GC, in terms of the response selectivities and response profiles.

Acetylcholine↗

PubMed1986

Gustatory cortex in the rat. II. Thalamocortical projections.

The thalamic relay for lingual tactile, thermal, and gustatory sensibility was defined electrophysiologically in the rat. Subsequently, injections of tritiated leucine were centered in these functionally defined locations in separate series of rats. Following suitable survival periods, the brains were processed for autoradiographic tracing of axonal projections. After injections confined to the thalamic gustatory relay, labeled fibers terminated in agranular insular cortex. These results provide support for our previous experiments correlating neurophysiological localization of rat gustatory cortex and regional cytoarchitecture, and contrast with the traditional assignation of gustatory cortex to the granular insular area.

Animals↗

PubMed2006

Differential taste coding of salt and acid by correlative activities between taste-sensitive neuron types in rat gustatory cortex.

Using a multi-electrode recording technique, the present study aimed to elucidate the role of broadly-tuned taste-sensitive neurons in the rat gustatory cortex in discriminating between salt and acid. A majority of taste-sensitive neurons (94/119 neurons; 78%) were classified as NaCl (N)-, HCl (H)- or NaCl and HCl (NH)-best neurons. Of 63 neuron pairs (94 neurons), 31 showed significant peaks and/or troughs in their cross-correlograms (CCs) during taste stimulation periods. During NaCl stimulation, the incidence of significant correlation and the mean frequency of correlated discharges (FC) in the N/N and NH/NH pairs were higher than those in the other best-taste pairs. In contrast, during HCl stimulation both indices in the N/N or H/H pairs were very low, while those in the NH/NH pairs were high. These results suggest that (1) correlated activities between N-best neurons and those between NH-best neurons play a significant role in taste quality coding of salt, and that (2) correlated activities between NH-best neurons may be important for sour taste coding as well. Peak formation in CCs tended to be more frequent in the homo-types (N/N, H/H and NH/NH pairs) than in the hetero-types (N/NH, N/H and H/NH pairs). In contrast, troughs were observed mostly in the hetero-types. Inhibitory interaction in hetero-type pairs together with coactivation in homo-type pairs may enhance taste discrimination by taste-sensitive neuron populations.

Algorithms↗

PubMed1992

Taste avoidance, but not aversion, learning in rats lacking gustatory cortex.

Control rats rapidly learned to avoid drinking either a sucrose solution (Experiment 1) or a NaCl solution (Experiment 2) when the taste was paired with illness. These rats also produced aversive reactivity to each of these solutions in a taste reactivity test. Rats that lacked gustatory cortex (GC) learned to avoid drinking sucrose and NaCl, albeit at a slower rate than control rats. GC rats failed to display aversive reactivity to these tastes. The GC rats did show normal aversive reactivity to a strong quinine HCl solution during additional tests. It is suggested that the avoidance developed by GC rats did not entail a palatability shift of the conditional stimulus as it did in control rats. This altered learning strategy may account for the consistent learning deficits found in GC rats trained to avoid tastes.

Animals↗