Pontine Gustatory Activity Is Altered by Electrical Stimulation in the Central Nucleus of the Amygdala

2001 ◽  
Vol 85 (2) ◽  
pp. 770-783 ◽  
Author(s):  
Robert F. Lundy ◽  
Ralph Norgren
Keyword(s):  
Electrical Stimulation ◽  
Citric Acid ◽  
Relative Effectiveness ◽  
Central Nucleus ◽  
Baseline Activity ◽  
Descending Input ◽  
Gustatory Information ◽  
Stimulus Effectiveness ◽  
Chemical Selectivity ◽  
Anatomical Evidence

Visceral signals and experience modulate the responses of brain stem neurons to gustatory stimuli. Both behavioral and anatomical evidence suggests that this modulation may involve descending input from the forebrain. The present study investigates the centrifugal control of gustatory neural activity in the parabrachial nucleus (PBN). Extracellular responses were recorded from 51 single PBN neurons during application of sucrose, NaCl, NaCl mixed with amiloride, citric acid, and QHCl with or without concurrent electrical stimulation in the ipsilateral central nucleus of the amygdala (CeA). Based on the sapid stimulus that evoked the greatest discharge, 3 neurons were classified as sucrose-best, 32 as NaCl-best, and 16 as citric acid-best. In most of the neurons sampled, response rates to an effective stimulus were either inhibited or unchanged during electrical stimulation of the CeA. Stimulation in the CeA was without effect in two sucrose-best neurons, nine NaCl-best neurons, and one citric acid-best neuron. Suppression was evident in 1 sucrose-best neuron, 18 NaCl-best neurons, and 15 citric acid-best neurons. In NaCl-best neurons inhibited by CeA stimulation, the magnitude of the effect was similar for spontaneous activity and responses to the five taste stimuli. Nonetheless, the inhibitory modulation of gustatory sensitivity increased the relative effectiveness of NaCl resulting in narrower chemical selectivity. For citric acid–best neurons, the magnitude of inhibition produced by CeA activation increased with an increase in stimulus effectiveness. The responses to citric acid were inhibited significantly more than the responses to all other stimuli with the exception of NaCl mixed with amiloride. The overall effect was to change these CA-best neurons to CA/NaCl-best neurons. In a smaller subset of NaCl-best neurons ( n = 5), CeA stimulation augmented the responsiveness to NaCl but was without effect on the other stimuli or on baseline activity. It appears that electrical stimulation in the CeA modulates response intensity, as well as the type of gustatory information that is transmitted in a subset of NaCl-best neurons. These findings provide an additional link between the amygdala and the PBN in the control of NaCl intake, modulating the response and the chemical selectivity of an amiloride-sensitive Na+-detecting input pathway.

scholarly journals Amygdalofugal Influence on Processing of Taste Information in the Nucleus of the Solitary Tract of the Rat

2010 ◽  
Vol 104 (2) ◽  
pp. 726-741 ◽  
Author(s):  
Yi Kang ◽  
Robert F. Lundy
Keyword(s):  
Electrical Stimulation ◽  
Citric Acid ◽  
Neural Coding ◽  
Central Nucleus ◽  
Perceptual Similarity ◽  
Gustatory System ◽  
Solitary Tract ◽  
Neurophysiological Mechanism ◽  
Central Synapse ◽  
Stimulation Of

Previous studies have shown that corticofugal input to the first central synapse of the ascending gustatory system, the nucleus of the solitary tract (NST), can alter the way taste information is processed. Activity in other forebrain structures, such as the central nucleus of the amygdala (CeA), similarly influence activation of NST taste cells, although the effects of amygdalofugal input on neural coding of taste information is not well understood. The present study examined responses of 110 NST neurons to 15 taste stimuli before, during, and after electrical stimulation of the CeA in rats. The taste stimuli consisted of different concentrations of NaCl (0.03, 0.1, 0.3 M), sucrose (0.1, 0.3, 1.0 M), citric acid (0.005, 0.01 M), quinine HCl (0.003, 0.03 M), and 0.03 M MSG, 0.1 M KCl, as well as 0.1 M NaCl, 0.01 M citric acid, and 0.03 M MSG mixed with 10 μM amiloride. In 66% of NST cells sampled (73/110) response rates to the majority of effective taste stimuli were either inhibited or augmented. Nevertheless, the magnitude of effect across stimuli was often differential, which provides a neurophysiological mechanism to alter neural coding. Subsequent analysis of across-unit patterns showed that amygdalofugal input plays a role in shaping spatial patterns of activation and could potentially influence the perceptual similarity and/or discrimination of gustatory stimuli by altering this feature of neural coding.

Activity in the Hypothalamus, Amygdala, and Cortex Generates Bilateral and Convergent Modulation of Pontine Gustatory Neurons

2004 ◽  
Vol 91 (3) ◽  
pp. 1143-1157 ◽  
Author(s):  
Robert F. Lundy ◽  
Ralph Norgren
Keyword(s):  
Citric Acid ◽  
Hypothalamic Stimulation ◽  
Central Nucleus ◽  
Parabrachial Nucleus ◽  
Stimulus Response ◽  
Sodium Appetite ◽  
Response Profiles ◽  
Chemical Selectivity ◽  
Gustatory Neurons ◽  
Stimulation Of

Evidence suggests that centrifugal modulation of brain stem gustatory cells might play a role in the elaboration of complex taste-guided behaviors like conditioned taste aversion and sodium appetite. We previously showed that activity in one forebrain area, the central nucleus of the amygdala (CeA), increased the chemical selectivity of taste cells in the parabrachial nucleus (PBN). The present study investigates how activity in 2 other similarly interconnected forebrain sites, the lateral hypothalamus (LH) and gustatory cortex (GC), might influence PBN gustatory processing in rats. The potential convergence of descending inputs from these sites, as well as the CeA, was also evaluated. After anesthesia (35 mg/kg Nembutal ip), 70 PBN gustatory neurons were tested before, during, and after electrical stimulation of these forebrain sites, while responding to 0.3 M sucrose, 0.1 M NaCl, 0.01 M citric acid, and 0.003 M QHCl. Although each forebrain site modulated taste-evoked responses, more PBN neurons were influenced by stimulation of the GC (67%) and CeA (73%) than of the LH (48%). Activation of cortex (71%) and amygdala (85%) most often produced inhibition, whereas inhibition and excitation occurred equally often during hypothalamic stimulation. Of the neurons tested for convergence ( n = 60), 88% were influenced by ≥1 of the 3 sites. Twenty were modulated by stimulation at all 3 sites and another 17 by 2 of the 3 sites. The net effect of centrifugal modulation was to sharpen the across-stimulus response profiles of PBN cells, particular with regard to the NaCl- and citric acid-best cells.

Temporal resolution of neurons in cat inferior colliculus to intracochlear electrical stimulation: effects of neonatal deafening and chronic stimulation

1995 ◽  
Vol 73 (2) ◽  
pp. 449-467 ◽  
Author(s):  
R. Snyder ◽  
P. Leake ◽  
S. Rebscher ◽  
R. Beitel
Keyword(s):  
Electrical Stimulation ◽  
Inferior Colliculus ◽  
Temporal Resolution ◽  
Transfer Functions ◽  
Discharge Rate ◽  
Pulse Frequency ◽  
Acoustic Stimulation ◽  
Acute Experiment ◽  
Sustained Response ◽  
Central Nucleus

1. Cochlear implants have been available for > 20 yr to profoundly deaf adults who have lost their hearing after acquiring language. The success of these cochlear prostheses has encouraged the application of implants in prelingually deaf children as young as 2 yr old. To further characterize the consequences of chronic intracochlear electrical stimulation (ICES) on the developing auditory system, the temporal-response properties of single neurons in the inferior colliculus (IC) were recorded in deafened anesthetized cats. 2. The neurons were excited by unilateral ICES with the use of a scala tympani stimulating electrode implanted in the left cochlea. The electrodes were modeled after those used in cochlear implant patients. Responses of 443 units were recorded extracellularly in the contralateral (right) IC with the use of tungsten microelectrodes. Recordings were made in three groups of adult animals: neonatally deafened/chronically stimulated animals (192 units), neonatally deafened/unstimulated animals (80 units), and adult-deafened/prior normal-hearing animals (171 units). The neonatally deafened cats were deafened by multiple intramuscular injections of neomycin sulfate and never developed demonstrable hearing. Most of the deafened, chronically stimulated animals were implanted at 6 wk of age and stimulated at suprathreshold levels for 4 h/day for 3-6 mo. The unstimulated animals were implanted as adults at least 2 wk before the acute physiological experiment and were left unstimulated until the acute experiment was conducted. Prior-normal adults were deafened and implanted at least 2 wk before the acute experiment. 3. IC units were isolated with the use of a search stimulus consisting of three cycles of a 100-Hz sinusoid. Most units responded to sinusoidal stimulation with either an onset response or a sustained response. Onset units were the predominant unit found in the external nucleus, whereas sustained units were found almost exclusively in the central nucleus. The temporal resolution of sustained response units was measured with the use of pulse trains of increasing frequency and calculating the discharges/pulse. 4. The range of electrical pulse frequencies to which IC units responded in a temporally synchronized manner was comparable with that produced by acoustic stimulation. The discharge rate/pulse-versus-pulse frequency transfer functions of IC units were uniformly low-pass, although they varied widely in their cutoff frequencies. This variation in pulse response was partially correlated with the unit's response to sinusoids. Most onset neurons responded only to pulse frequencies below 20 pulses per second (pps). Most sustained units responded best to pulse frequencies < 100 pps, and most ceased to respond to pulse frequencies > 300 pps.(ABSTRACT TRUNCATED AT 400 WORDS)

Modulation of Parabrachial Taste Neurons by Electrical and Chemical Stimulation of the Lateral Hypothalamus and Amygdala

2005 ◽  
Vol 93 (3) ◽  
pp. 1183-1196 ◽  
Author(s):  
Cheng-Shu Li ◽  
Young K. Cho ◽  
David V. Smith
Keyword(s):  
Citric Acid ◽  
Lateral Hypothalamus ◽  
Ingestive Behavior ◽  
Central Nucleus ◽  
Homocysteic Acid ◽  
Quinine Hydrochloride ◽  
Neural Substrate ◽  
Parabrachial Nuclei ◽  
Gustatory Neurons ◽  
Stimulation Of

The lateral hypothalamus (LH) and the central nucleus of the amygdala (CeA) exert an influence on ingestive behavior and are reciprocally connected to gustatory and viscerosensory areas, including the nucleus of the solitary tract (NST) and the parabrachial nuclei (PbN). We investigated the effects of LH and CeA stimulation on the activity of 101 taste-responsive neurons in the hamster PbN. Eighty three of these neurons were antidromically activated by stimulation of these sites; 57 were antidromically driven by both. Of these 83 neurons, 21 were also orthodromically activated—8 by the CeA and 3 by the LH. Additional neurons were excited ( n = 5) or inhibited ( n = 8) by these forebrain nuclei but not antidromically activated. Taste stimuli were: 0.032 M sucrose, 0.032 M sodium chloride (NaCl), 0.032 M quinine hydrochloride (QHCl), and 0.0032 M citric acid. Among the 34 orthodromically activated neurons, more sucrose-best neurons were excited than inhibited, whereas the opposite occurred for citric-acid- and QHCl-best cells. Neurons inhibited by the forebrain responded significantly more strongly to citric acid and QHCl than cells excited by these sites. The effects of electrical stimulation were mimicked by microinjection of dl-homocysteic acid, indicating that cells at these forebrain sites were responsible for these effects. These data demonstrate that many individual PbN gustatory neurons project to both the LH and CeA and that these areas modulate the gustatory activity of a subset of PbN neurons. This neural substrate is likely involved in the modulation of taste activity by physiological and experiential factors.

Taste Responses of Neurons of the Hamster Solitary Nucleus Are Enhanced by Lateral Hypothalamic Stimulation

2002 ◽  
Vol 87 (4) ◽  
pp. 1981-1992 ◽  
Author(s):  
Young K. Cho ◽  
Cheng-Shu Li ◽  
David V. Smith
Keyword(s):  
Electrical Stimulation ◽  
Brain Stem ◽  
Taste Preference ◽  
Gastric Distension ◽  
Physiological Factors ◽  
Homocysteic Acid ◽  
Ipsilateral Stimulation ◽  
Gustatory Information ◽  
The Brain ◽  
Stimulation Of

Gustatory responses in the brain stem are modifiable by several physiological factors, including blood insulin and glucose, intraduodenal lipids, gastric distension, and learning, although the neural substrates for these modulatory effects are not known. Stimulation of the lateral hypothalamus (LH) produces increases in food intake and alterations in taste preference behavior, whereas damage to this area has opposite effects. In the present study, we investigated the effects of LH stimulation on the neural activity of taste-responsive cells in the nucleus of the solitary tract (NST) of the hamster. Bipolar stimulating electrodes were bilaterally implanted in the LH, and the responses of 99 neurons in the NST, which were first characterized for their taste sensitivities, were tested for their response to both ipsilateral and contralateral LH stimulation. Half of the taste-responsive cells in the NST (49/99) were modulated by LH stimulation. Contralateral stimulation was more often effective (41 cells) than ipsilateral (13 cells) and always excitatory; 10 cells were excited bilaterally. Six cells were inhibited by ipsilateral stimulation. A subset of these cells ( n = 13) was examined for the effects of microinjection of dl-homocysteic acid (DLH), a glutamate receptor agonist, into the LH. The effects of electrical stimulation were completely mimicked by DLH, indicating that cell somata in and around the LH are responsible for these effects. Other cells ( n = 14) were tested for the effects of electrical stimulation of the LH on the responses to stimulation of the tongue with 0.032 M sucrose, NaCl, and quinine hydrochloride, and 0.0032 M citric acid. Responses to taste stimuli were more than doubled by the excitatory influence of the LH. These data show that the LH, in addition to its role in feeding and metabolism, exerts descending control over the processing of gustatory information through the brain stem.

Superior Colliculus Neurons Use Distinct Operational Modes in the Integration of Multisensory Stimuli

2005 ◽  
Vol 93 (5) ◽  
pp. 2575-2586 ◽  
Author(s):  
Thomas J. Perrault ◽  
J. William Vaughan ◽  
Barry E. Stein ◽  
Mark T. Wallace
Keyword(s):  
Superior Colliculus ◽  
Dynamic Range ◽  
Relative Effectiveness ◽  
Sensory Information ◽  
General Rule ◽  
Temporal Relationships ◽  
Superior Colliculus Neurons ◽  
Stimulus Effectiveness ◽  
Operational Modes ◽  
Substantial Heterogeneity

Many neurons in the superior colliculus (SC) integrate sensory information from multiple modalities, giving rise to significant response enhancements. Although enhanced multisensory responses have been shown to depend on the spatial and temporal relationships of the stimuli as well as on their relative effectiveness, these factors alone do not appear sufficient to account for the substantial heterogeneity in the magnitude of the multisensory products that have been observed. Toward this end, the present experiments have revealed that there are substantial differences in the operations used by different multisensory SC neurons to integrate their cross-modal inputs, suggesting that intrinsic differences in these neurons may also play an important deterministic role in multisensory integration. In addition, the integrative operation employed by a given neuron was found to be well correlated with the neuron's dynamic range. In total, four categories of SC neurons were identified based on how their multisensory responses changed relative to the predicted addition of the two unisensory inputs as stimulus effectiveness was altered. Despite the presence of these categories, a general rule was that the most robust multisensory enhancements were seen with combinations of the least effective unisensory stimuli. Together, these results provide a better quantitative picture of the integrative operations performed by multisensory SC neurons and suggest mechanistic differences in the way in which these neurons synthesize cross-modal information.

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