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

1985 ◽  
Vol 53 (6) ◽  
pp. 1356-1369 ◽  
Author(s):  
T. Yamamoto ◽  
N. Yuyama ◽  
T. Kato ◽  
Y. Kawamura
Keyword(s):  
Cortical Neurons ◽  
Neural Coding ◽  
Response Pattern ◽  
Present Report ◽  
Correlation Coefficients ◽  
Taste Quality ◽  
Pattern Theory ◽  
Response Characteristics ◽  
Basic Taste ◽  
Neuron Response

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)

Gustatory responses of cortical neurons in rats. III. Neural and behavioral measures compared

1985 ◽  
Vol 53 (6) ◽  
pp. 1370-1386 ◽  
Author(s):  
T. Yamamoto ◽  
N. Yuyama ◽  
T. Kato ◽  
Y. Kawamura
Keyword(s):  
Cortical Neurons ◽  
Response Pattern ◽  
Correlation Coefficients ◽  
Neural Responses ◽  
Behavioral Measures ◽  
Anterior Portion ◽  
Pattern Theory ◽  
Basic Taste ◽  
Neuron Response ◽  
Solution Intake

The responses of 39 cortical neurons to 13 kinds of taste stimuli including the four putative basic taste solutions (sucrose, NaCl, HCl, and quinine HCl) applied to the anterior portion of the tongue were recorded extracellularly in lightly anesthetized rats. The neural responses were analyzed in terms of the four hypotheses of quality coding: across-neuron response pattern, labeled-line, matrix pattern, and across-region response pattern notions. Animals were given a conditioned taste aversion to one of the 11 stimuli by pairing it with a gastrointestinal illness caused by intraperitoneal injection of 0.15 M LiCl. Behavioral taste profiles were constructed for each stimulus from the suppression of rate of drinking, which indicates the extent of generalization of aversion to each of the four basic taste stimuli. Neural taste profiles of each taste stimulus, which indicate the relation of the taste of a stimulus to each taste of the four basic stimuli, differed more or less depending on the kind of quality-coding notions employed. Among the four analyses, across-region correlation coefficients that were derived from an across-region response-pattern theory showed the highest correlation with the behavioral suppression rates. Therefore we conclude that processing of taste information in the cortex involves differences in both response magnitude across neurons and the spatial localization of those neurons. Fluid intake per day of each of the 12 taste solutions was measured by the single-bottle preference method. When the amount of intake was described in terms of an hedonic index (HI), which indicates the hedonic aspect of the taste of each solution, HI's for sucrose, NaCl, HCl, and quinine were 1.17, 0.43, -0.49, and -0.89, respectively. These values represent the degree of deviation of solution intake above (i.e., preferable) or below (aversive) the standard water intake. Then, HI's were calculated for each of the 12 taste stimuli based on the neural taste profiles and actual HI's for each of the four basic taste stimuli. The correlations between the calculated and the actual (or behaviorally obtained) HI's were very high (ranging from 0.832 to 0.941). This result suggests that the hedonic dimension of taste can be matched well by any one of the four proposed hypotheses.

Taste responses of cortical neurons in freely ingesting rats

1989 ◽  
Vol 61 (6) ◽  
pp. 1244-1258 ◽  
Author(s):  
T. Yamamoto ◽  
R. Matsuo ◽  
Y. Kiyomitsu ◽  
R. Kitamura
Keyword(s):  
Cortical Neurons ◽  
Correlation Coefficients ◽  
Entropy Measure ◽  
Response Patterns ◽  
Gustatory System ◽  
Basic Taste ◽  
Quinine Hydrochloride ◽  
Excitatory Responses

1. Activities of 35 taste-responsive neurons in the cortical gustatory area were recorded with chronically implanted fine wires in freely ingesting Wistar rats. Quantitative analyses were performed on responses to distilled water, food solution, and four taste stimuli: sucrose, NaCl, HCl, and quinine hydrochloride. 2. Taste-responsive neurons were classified into type-1 and type-2 groups according to the response patterns to licking of the six taste stimuli. Type-1 neurons (n = 29) responded in excitatory or inhibitory directions to one or more of the taste stimuli. Type-2 neurons (n = 6) showed responses in different directions depending upon palatability of the liquids to rats: neurons showing excitatory (or inhibitory) responses to palatable stimuli exhibited inhibitory (or excitatory) responses to unpalatable stimuli. 3. Correlation coefficients of responses to pairs of stimuli across neurons suggested that palatable stimuli (water, food solution, sucrose, and NaCl) and unpalatable stimuli (HCl and quinine) elicited reciprocal (excitatory vs. inhibitory) responses in type-2 neurons, whereas type-1 neurons showed positively correlated responses to specific combinations of stimuli such as food solution and NaCl, sucrose and HCl, NaCl and quinine, and HCl and quinine. 4. A tendency toward equalization of effectiveness in eliciting responses among the four basic taste stimuli was detected on the cortex. The ratios of mean evoked responses in 29 type-1 neurons in comparison with spontaneous rate (4.4 spikes/s) were 1.7, 1.9, 1.8, and 1.9 for sucrose, NaCl, HCl, and quinine, respectively. 5. The breadth of responsiveness to the four basic taste stimuli was quantified by means of the entropy measure introduced by Smith and Travers (33). The mean entropy value was 0.540 for 29 type-1 neurons, which was similar to 0.588 previously reported for rat chorda tympani fibers, suggesting that breadth of tuning is not more narrowly tuned in a higher level of the gustatory system in the rat. 6. Convergent inputs of other sensory modalities were detected exclusively in type-1 neurons. Thirteen (45%) of 29 type-1 neurons also responded to cold and/or warm water, but none of 6 type-2 neurons responded to thermal stimuli. Two (7%) of 29 type-1 neurons responded to almond and acetic acid odors, but the 6 type-2 neurons did not. Two (13%) of 16 type-1 neurons responded to interperitoneal injection of LiCl, which is known to induce gastrointestinal disorders, with a latency of approximately 5 min, but 4 type-2 neurons tested were not responsive to this stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Gustatory neural coding in the monkey cortex: stimulus quality

1991 ◽  
Vol 66 (4) ◽  
pp. 1156-1165 ◽  
Author(s):  
V. L. Smith-Swintosky ◽  
C. R. Plata-Salaman ◽  
T. R. Scott
Keyword(s):  
Cortical Neurons ◽  
Neural Coding ◽  
Monosodium Glutamate ◽  
Stimulus Array ◽  
Cortical Region ◽  
Stimulus Similarity ◽  
Somatosensory Stimulation ◽  
Wide Range ◽  
Response Profiles ◽  
Stimulation Of

1. Extracellular action potentials were recorded from 50 single neurons in the insular-opercular cortex of two alert cynomolgus monkeys during gustatory stimulation of the tongue and palate. 2. Sixteen stimuli, including salts, sugars, acids, alkaloids, monosodium glutamate, and aspartame, were chosen to represent a wide range of taste qualities. Concentrations were selected to elicit a moderate gustatory response, as determined by reference to previous electrophysiological data or to the human psychophysical literature. 3. The cortical region over which taste-evoked activity could be recorded included the frontal operculum and anterior insula, an area of approximately 75 mm3. Taste-responsive cells constituted 50 (2.7%) of the 1,863 neurons tested. Nongustatory cells responded to mouth movement (20.7%), somatosensory stimulation of the tongue (9.6%), stimulus approach or anticipation (1.7%), and tongue extension (0.6%). The sensitivities of 64.6% of these cortical neurons could not be identified by our stimulation techniques. 4. Taste cells had low spontaneous activity levels (3.7 +/- 3.0 spikes/s, mean +/- SD) and showed little inhibition. They were moderately broadly tuned, with a mean entropy coefficient of 0.76 +/- 0.17. Excitatory responses were typically not robust. 5. Hierarchical cluster analysis was used to determine whether neurons could be divided into discrete types, as defined by their response profiles to the entire stimulus array. There was an apparent division of response profiles into four general categories, with primary sensitivities to sodium (n = 18), glucose (n = 15), quinine (n = 12), and acid (n = 5). However, these categories were not statistically independent. Therefore the notion of functionally distinct neuron types was not supported by an analysis of the distribution of response profiles. It was the case, however, that neurons in the sodium category could be distinguished from other neurons by their relative specificity. 6. The similarity among the taste qualities represented by this stimulus array was assessed by calculating correlations between the activity profiles they elicited from these 50 neurons. The results generally confirmed expectations derived from human psychophysical studies. In a multidimensional representation of stimulus similarity, there were groups that contained acids, sodium salts, and chemicals that humans label bitter and sweet. 7. The small proportion of insular-opercular neurons that are taste sensitive and the low discharge rates that taste stimuli are able to evoke from them suggest a wider role for this cortical area than just gustatory coding.(ABSTRACT TRUNCATED AT 400 WORDS)

Glutamate receptors in cortical plasticity: molecular and cellular biology

1997 ◽  
Vol 77 (1) ◽  
pp. 217-255 ◽  
Author(s):  
L. Kaczmarek ◽  
M. Kossut ◽  
J. Skangiel-Kramska
Keyword(s):  
Glutamate Receptors ◽  
Cortical Neurons ◽  
Cortical Plasticity ◽  
Excitatory Input ◽  
Cellular Biology ◽  
Metabotropic Receptors ◽  
Functional Studies ◽  
Neuron Response ◽  
Plastic Changes ◽  
Protein Immunoreactivity

Glutamate receptors (GluRs) provide the major excitatory input to cortical neurons. Four main subtypes of GluRs are distinguished, namely, N-methyl-D-aspartate, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid, kainate, and metabotropic receptors. All of them have been implicated in neuronal plasticity, and this paper reviews data that may be pertinent to the role played by GluRs in neocortical plasticity both in adult animals as well as during postnatal development. Emphasis is given to receptor distribution analyzed by various means, such as physiological responses, ligand binding as revealed by receptor autoradiography, and expression of receptor subunits at both mRNA and protein (immunoreactivity) levels. Possible mechanisms of involvement of GluRs in plastic changes on cortical neuron response are reviewed, and data on up- and downregulation of GluRs in neocortical plasticity are summarized. Functional studies involving either activation or blocking, and effects of such manipulation on cortical plasticity are discussed.

scholarly journals Taste quality representation in the human brain

2019 ◽  
Author(s):  
Jason A. Avery ◽  
Alexander G. Liu ◽  
John E. Ingeholm ◽  
Cameron D. Riddell ◽  
Stephen J. Gotts ◽  
...  
Keyword(s):  
Human Brain ◽  
Cortical Neurons ◽  
Brain Regions ◽  
Taste Quality ◽  
7 Tesla ◽  
Mammalian Brain ◽  
High Magnetic Field Strength ◽  
Magnetic Resonance Imaging Mri ◽  
Spatial Locations ◽  
Univariate Analyses

SUMMARYIn the mammalian brain, the insula is the primary cortical substrate involved in the perception of taste. Recent imaging studies in rodents have identified a gustotopic organization in the insula, whereby distinct insula regions are selectively responsive to one of the five basic tastes. However, numerous studies in monkeys have reported that gustatory cortical neurons are broadly-tuned to multiple tastes, and tastes are not represented in discrete spatial locations. Neuroimaging studies in humans have thus far been unable to discern between these two models, though this may be due to the relatively low spatial resolution employed in taste studies to date. In the present study, we examined the spatial representation of taste within the human brain using ultra-high resolution functional magnetic resonance imaging (MRI) at high magnetic field strength (7-Tesla). During scanning, participants tasted sweet, salty, sour and tasteless liquids, delivered via a custom-built MRI-compatible tastant-delivery system. Our univariate analyses revealed that all tastes (vs. tasteless) activated primary taste cortex within the bilateral dorsal mid-insula, but no brain region exhibited a consistent preference for any individual taste. However, our multivariate searchlight analyses were able to reliably decode the identity of distinct tastes within those mid-insula regions, as well as brain regions involved in affect and reward, such as the striatum, orbitofrontal cortex, and amygdala. These results suggest that taste quality is not represented topographically, but by a combinatorial spatial code, both within primary taste cortex as well as regions involved in processing the hedonic and aversive properties of taste.

Concept of neuron types in gustation in the rat

1979 ◽  
Vol 42 (5) ◽  
pp. 1390-1409 ◽  
Author(s):  
D. C. Woolston ◽  
R. P. Erickson
Keyword(s):  
Dimensional Space ◽  
Correlation Coefficients ◽  
Hierarchical Cluster ◽  
Scaling Analysis ◽  
Peripheral Neurons ◽  
Neuron Response ◽  
The Matrix ◽  
Formal Taxonomy ◽  
Response Profiles ◽  
Mathematical Techniques

1. In taste neurophysiology, from Pfaffmann's (49, 50) pioneering work until the present, the possibility of types of neurons corresponding in some sense with the "primary" taste qualities of Henning (33) has been entertained: recently types of gustatory neurons in peripheral nerves have been established according to which of the four classical stimuli is the "best stimulus." However, considerable variation occurs in the response profiles within neurons classified as belonging to the same type. The purpose of this research is to determine, using mathematical techniques where appropriate, if the within-type variation is spurious or, instead, indicates the absence of a typology of taste neurons. The data used were counts of the spike discharges of 50 individual taste neurons in the nucleus of the solitary tract of the rat, evoked by 32 diverse chemical stimuli. 2. Using as input the matrix of Pearson r correlation coefficients calculated for the responses of all pairings of neurons to all stimuli, multidimensional scaling analysis revealed a two-dimensional space in which no clear groupings of neurons occurred. 3. In a hierarchical cluster analysis of the neuron response profile similarities, no evidence of grouping was found, suggesting a more-or-less continuous variation among neurons. 4. When the organization of the 32 stimuli utilized was studied by the same techniques, no clear evidence for stimulus types was found, although the possibility of two stimulus types--"sweet" and "nonsweet"--was raised. 5. Construction of a joint neuron-stimulus space supported a spatial model of taste neuron-stimulus interaction, while analysis of the number and pattern of high correlations among neurons--even after allowance for attenuation due to measurement error--failed to support the notion of types of taste neurons with identical response profiles. 6. Aspects of the logical role of types of neurons in gustatory coding were discussed, and the results and methods of the present investigation were related to classification schemes for neurons in general. Suggestions for a formal taxonomy of neurons were given. 7. It should be emphasized that the present study and conclusions are of second-order, CNS neurons, whereas the studies advocating the presence of neurons types were of peripheral neurons. Taken together, the implication to be drawn from these studies is that if neural types do exist in peripheral taste nerves, the typology is lost at the first synapse and is thus unavailable to the CNS for coding purposes, at least in the rat.

Adaptation and Temporal Decorrelation by Single Neurons in the Primary Visual Cortex

2003 ◽  
Vol 89 (6) ◽  
pp. 3279-3293 ◽  
Author(s):  
Xiao-Jing Wang ◽  
Yinghui Liu ◽  
Maria V. Sanchez-Vives ◽  
David A. McCormick
Keyword(s):  
Cortical Neurons ◽  
Neural Coding ◽  
Model Neuron ◽  
Ionic Currents ◽  
Cellular Mechanism ◽  
Membrane Properties ◽  
Sensory Inputs ◽  
V1 Neurons ◽  
Temporal Correlations ◽  
Temporal Decorrelation

Limiting redundancy in the real-world sensory inputs is of obvious benefit for efficient neural coding, but little is known about how this may be accomplished by biophysical neural mechanisms. One possible cellular mechanism is through adaptation to relatively constant inputs. Recent investigations in primary visual (V1) cortical neurons have demonstrated that adaptation to prolonged changes in stimulus contrast is mediated in part through intrinsic ionic currents, a Ca2+-activated K+ current ( IKCa) and especially a Na+-activated K+ current ( IKNa). The present study was designed to test the hypothesis that the activation of adaptation ionic currents may provide a cellular mechanism for temporal decorrelation in V1. A conductance-based neuron model was simulated, which included an IKCa and an IKNa. We show that the model neuron reproduces the adaptive behavior of V1 neurons in response to high contrast inputs. When the stimulus is stochastic with 1/ f 2 or 1/ f-type temporal correlations, these autocorrelations are greatly reduced in the output spike train of the model neuron. The IKCa is effective at reducing positive temporal correlations at approximately 100-ms time scale, while a slower adaptation mediated by IKNa is effective in reducing temporal correlations over the range of 1–20 s. Intracellular injection of stochastic currents into layer 2/3 and 4 (pyramidal and stellate) neurons in ferret primary visual cortical slices revealed neuronal responses that exhibited temporal decorrelation in similarity with the model. Enhancing the slow afterhyperpolarization resulted in a strengthening of the decorrelation effect. These results demonstrate the intrinsic membrane properties of neocortical neurons provide a mechanism for decorrelation of sensory inputs.

scholarly journals Effects of spectral and temporal disruption on cortical encoding of gerbil vocalizations

2013 ◽  
Vol 110 (5) ◽  
pp. 1190-1204 ◽  
Author(s):  
Maria Ter-Mikaelian ◽  
Malcolm N. Semple ◽  
Dan H. Sanes
Keyword(s):  
Cortical Neurons ◽  
Neural Coding ◽  
Human Performance ◽  
Animal Communication ◽  
Human Perception ◽  
Primary Auditory Cortex ◽  
Sufficient Information ◽  
Spectral Bands ◽  
Stable Representation ◽  
Discharge Patterns

Animal communication sounds contain spectrotemporal fluctuations that provide powerful cues for detection and discrimination. Human perception of speech is influenced both by spectral and temporal acoustic features but is most critically dependent on envelope information. To investigate the neural coding principles underlying the perception of communication sounds, we explored the effect of disrupting the spectral or temporal content of five different gerbil call types on neural responses in the awake gerbil's primary auditory cortex (AI). The vocalizations were impoverished spectrally by reduction to 4 or 16 channels of band-passed noise. For this acoustic manipulation, an average firing rate of the neuron did not carry sufficient information to distinguish between call types. In contrast, the discharge patterns of individual AI neurons reliably categorized vocalizations composed of only four spectral bands with the appropriate natural token. The pooled responses of small populations of AI cells classified spectrally disrupted and natural calls with an accuracy that paralleled human performance on an analogous speech task. To assess whether discharge pattern was robust to temporal perturbations of an individual call, vocalizations were disrupted by time-reversing segments of variable duration. For this acoustic manipulation, cortical neurons were relatively insensitive to short reversal lengths. Consistent with human perception of speech, these results indicate that the stable representation of communication sounds in AI is more dependent on sensitivity to slow temporal envelopes than on spectral detail.

Taste responses in neurons in the nucleus of the solitary tract that do and do not project to the parabrachial pons

1995 ◽  
Vol 74 (1) ◽  
pp. 249-257 ◽  
Author(s):  
S. Monroe ◽  
P. M. Di Lorenzo
Keyword(s):  
Neural Coding ◽  
Stainless Steel Electrode ◽  
Solitary Tract ◽  
Neural Pathway ◽  
Electrophysiological Response ◽  
Steel Electrode ◽  
Response Characteristics ◽  
Electrophysiological Responses ◽  
Electrical Pulses ◽  
General Response

1. Mechanisms of neural coding of gustatory stimuli were studied in the nucleus of the solitary tract (NTS), the first relay in the neural pathway for gustation, in anesthetized rats. Taste-responsive NTS units were identified as "relay" or "nonrelay" based on the electrophysiological response to electrical pulses delivered to the parabrachial nucleus of the pons (PbN), the second relay in the neural pathway for gustation. Coding mechanisms in each group were analyzed separately. 2. Taste responses to sapid solutions of NaCl (0.1 M), HCl (0.01 M), quinine HCl (0.01 M), sucrose (0.5 M) and Na-saccharin (0.004 M) were recorded in single units in the NTS. After gustatory stimulation, electrophysiological responses to electrical stimulation of the taste-responsive part of the ipsilateral PbN were recorded. A 0.2-ms pulse was delivered at 75-250 microA at a rates of 1, 25, 50 and 100 pps through a bipolar stainless steel electrode. An antidromic response was defined as a time-locked spike that occurred at a fixed latency after PbN stimulation that followed high stimulation frequencies. A collision test also was performed. 3. Of 42 taste-responsive NTS units, 19 (45%) were relay units, 22 (52%) were nonrelay and 1 unit was activated orthodromically by PbN stimulation. Latencies of evoked spikes ranged from 1.75 to 4.0 ms 2.1 +/- 0.2 ms (mean +/- SE, median, 1.75 ms). 4. Examination of general response characteristics revealed few differences among relay and nonrelay units.(ABSTRACT TRUNCATED AT 250 WORDS)

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