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R Norgren

Publications and source records attributed to R Norgren.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1986

Convergence of lingual and palatal gustatory neural activity in the nucleus of the solitary tract.

The responses of 54 neurons to independent sapid stimulation of 4 taste receptor subpopulations associated with: (1) anterior tongue; (2) nasoincisor ducts; (3) soft palate; and (4) foliate papillae were recorded from the nucleus of the solitary tract (NST) of the Rat. Neurons responding to stimulation of receptor subpopulations in the anterior oral cavity (anterior tongue or nasoincisor ducts) were located more rostrally in the NST than neurons responding to stimulation of receptor subpopulations in the posterior oral cavity (soft palate or foliate papillae). Half of the sampled neurons responded exclusively to stimulation of one receptor subpopulation with the remaining neurons responsive to stimulation of two or more receptor subpopulations. The most common pattern of convergence observed was between responses arising from stimulation of the taste buds on the anterior tongue and those associated with the nasoincisor ducts of the hard palate. The sensitivity of NST neurons to anterior tongue and nasoincisor duct stimulation with the 4 standard taste stimuli was determined. When stimulating the anterior tongue, the order of effectiveness was NaCl greater than HCl greater than sucrose greater than quinine hydrochloride (QHCl). When the nasoincisor ducts were tested, however, the order of stimulus effectiveness was strikingly different: sucrose was the best stimulus, followed by HCl, NaCl, and QHCl. If both the anterior tongue and nasoincisor ducts are included, stimulation of taste receptors in the anterior oral cavity of the rat produces good responses to stimuli representing 3 of the 4 classical taste qualities: sweet, salty, and sour.

Animals↗
PubMed1986

Projections of thalamic gustatory and lingual areas in the monkey, Macaca fascicularis.

The efferent projections of the parvicellular division of the ventroposteromedial nucleus of the thalamus (VMPpc; thalamic taste area) were traced to cortex in Macaca fascicularis by using tritiated amino acid autoradiography. Labeled fascicles could be traced from VPMpc to two discrete regions of cortex. The primary efferent projection was located on ipsilateral insular-opercular cortex adjacent to the superior limiting sulcus and extended as far rostrally as the posterior lateral orbitofrontal cortex. An additional projection was located within primary somatosensory (SI) cortex subjacent to the anterior subcentral sulcus. Following autoradiographic injections in VPM, the trigeminal somatosensory relay, a dense terminal plexus was labeled on SI cortex of both pre- and postcentral gyri, but not within insular-opercular cortex. The autoradiographic data were verified by injecting each cortical projection area with horseradish peroxidase (HRP) and observing the pattern of retrogradely labeled somata within the thalamus. Injections in the precentral gyrus near the anterior subcentral sulcus retrogradely labeled neurons within VPMpc, whereas injections further caudally near the floor of the central sulcus labeled neurons within VPM. Injections of HRP within opercular, insular, or posterior lateral orbitofrontal cortex retrogradely labeled neurons within VPMpc.

Animals↗
PubMed1986

Electromyographic analysis of the ingestion and rejection of sapid stimuli in the rat.

Previous behavior studies (Grill & Norgren, 1978) demonstrated that gustatory stimuli produce stereotyped orofacial movements that constitute the observable concomitants of ingestion and rejection. For further clarification of the relation between these orofacial movements (the buccal phase of ingestion) and the act of swallowing (the pharyngeal phase), electromyographic responses to intraoral sapid stimulation were recorded from a subset of orofacial and pharyngeal muscles in a freely moving chronic preparation. Activity in a jaw opening muscle (anterior digastric), a facial muscle (zygomatic), tongue protruder (genioglossus), tongue retractor (styloglossus), and a pharyngeal constrictor used in swallowing (thyropharyngeus) differentiated between ingestive sequences to water (W), sucrose (S), and NaCl (N) and a rejection response elicited by quinine monohydrochloride (Q). Ingestion responses to W, S, and N consisted of rhythmic alterations between genioglossus and styloglossus activity (intraoral licks) accompanied by episodic bursts of pharyngeal constrictor activity (swallowing). Both bout duration and the number of swallows increased at higher concentrations of S and N. In contrast, Q stimulation elicited a rejection response, characterized by several licks and followed by long duration contractions of the zygomatic and anterior digastric muscles (gapes). During gapes, styloglossus activity rather than genioglossus activity was simultaneous with that of the anterior digastric. At higher concentrations of Q, the latency to gape decreased and the latency to swallow increased. The earliest components of the response to S, N, or Q were virtually indistinguishable from one another, results suggesting that tactile (fluid) stimulation initiates the ingestive sequence and that gustatory stimuli modulate this ongoing activity.

Animals↗
PubMed1985

Integrated lateral hypothalamic neural responses to natural and artificial rewards and cue signals in the rat.

Effects of natural and intracranial electrical rewarding stimuli and cue signals were investigated while recording from single neurons in the rat lateral hypothalamus. The rat obtained both rewards using identical behavior, viz. licking. When both rewarding stimuli influenced a neuron, the responses were usually similar, i.e. both excitatory or both inhibitory. Only neurons that responded to either or both rewards acquired responses to tone cues, and these acquired responses were in the same direction as reward responses. The data indicate that the same single neuron in the lateral hypothalamus might be implicated in reward processes and learning.

Acoustic Stimulation↗
PubMed1984

Central projections of gustatory nerves in the rat.

The central distributions of gustatory and non-gustatory branches of cranial nerves V, VII, IX, and X were examined after application of horseradish peroxidase to the cut nerve. The nerves conveying gustatory information, chorda tympani (CT), greater superficial petrosal (GSP), lingual-tonsilar branch of IX (LT-IX), superior laryngeal branch of X (SL), distributed primarily to the lateral division of the nucleus of the solitary tract (NST) from its rostral pole to the obex. The CT and GSP distributions were coextensive and terminated most densely in the rostral pole of NST. The LT-IX distribution concentrated between this major CT/GSP distribution and the area postrema with a caudal extension into the interstitial nucleus of NST. This nerve also had a substantial projection, not found in other gustatory nerves, into the dorsolateral aspect of the medial NST. The SL distribution overlapped LT-IX in the caudal medulla. The lingual and inferior alveolar nerves, two oral trigeminal branches, projected to regions of NST innervated by the gustatory nerves. The cervical vagus nerve distributed primarily to the medial NST in the caudal half of the nucleus and exhibited only minimal overlap with gustatory nerve distributions. The nucleus of the solitary tract appears to have two major functional divisions--an anterior-lateral oral-gustatory half, and a posterior-medial visceral afferent half.

Afferent Pathways↗
PubMed1983

Afferent projections to the oral motor nuclei in the rat.

Projections to the trigeminal, facial, ambiguus, and hypoglossal motor nuclei were determined by using horseradish peroxidase histochemistry. Most of the afferent projections to these motor nuclei were from the brainstem reticular formation, frequently in areas adjacent to other synergetic motor nuclei. The reticular formation lateral to the hypoglossal nucleus and reticular structures surrounding the trigeminal motor nucleus projected to each of these other brainstem motor nuclei involved in oral-facial function. Afferent projections to these motor nuclei also were organized along the rostrocaudal axis. Within the reticular formation most of the afferent projections to the trigeminal motor nucleus originated rostral to the majority of neurons projecting to the hypoglossal and ambiguus nuclei, which in turn were rostral to the primary source of reticular afferents to the facial nucleus. In comparison, projections from the sensory trigeminal nuclei and nucleus of the solitary tract were sparse. The interneuron pools that project to the orofacial motoneurons provide one further link in understanding the brainstem substrates for integrating oral and ingestive behaviors.

Afferent Pathways↗
PubMed1983

Afferent interactions of cranial nerves involved in ingestion.

Substantial behavioral evidence implicates visceral afferent activity in the regulation of feeding behavior. One mechanism often suggested for this influence involves visceral afferent activity interacting with oral or gustatory afferent activity. This brief review summarizes the anatomical and electrophysiological evidence that indicates that such interactions might in fact take place. The available evidence for interactions between visceral and gustatory afferent messages is far from convincing, but perhaps only because the issue has seldom been addressed. The most direct tests suggested by the hypothesis advanced remain to be carried out.

Afferent Pathways↗
PubMed1982

The central projections of the trigeminal, facial, glossopharyngeal and vagus nerves: an autoradiographic study in the rat.

The central distributions of primary afferent axons in the facial, trigeminal (mandibular branch), glossopharyngeal, and vagal nerves of the rat have been re-examined using the autoradiographic tracing technique after injections of [3H]proline or [3H]leucine into their peripheral ganglia. Within the nucleus of the solitary tract (NST), the labeled terminals from VII, V, IX and X form a continuous distribution that spans the length of this nucleus. Sensory axons in VII terminate mainly within the lateral division of the rostral NST, although some of the terminals extend further caudally within the nucleus. Immediately caudal to the rostral NST, the distribution continues with major contributions from V and IX. Both are confined mainly to the lateral division of the NST, although some of the fibers in IX terminate within the medial division. Injections into the inferior ganglion of X confirm the extensive distribution of vagal axons as they ramify significantly within the lateral division, and virtually monopolize the medial division of the NST. Thus, the major zone of convergency for these 4 cranial nerves is the lateral division of the nucleus from the level of the entering fascicles of IX caudally to the level of the area postrema. Furthermore, only X has a crossed projection as vagal axons invade the commissural nucleus and the medial division of the contralateral NST. Vagal fibers also enter the area postrema bilaterally. Finally, some afferent fibers from VII, IX and X descend in the dorsal part of the spinal trigeminal tract and terminate within the marginal subdivision of the spinal trigeminal nucleus pars caudalis, as well as the dorsal horn of the cervical spinal cord.

Animals↗
PubMed1981

Taste aversions conditioned with intravenous copper sulfate: attenuation by ablation of the area postrema.

Borison and Wang identified the area postrema as the locus of chemoreceptors that mediate emetic reflexes elicited by blood-borne toxins. In the present experiments we have extended a systematic investigation of the afferent pathways mediating taste aversions by examining the effects of area postrema lesions on the aversions that follow either intravenous or intragastric administration of copper sulfate. Intrajugular cannulas were implanted in rats after ablation of the area postrema (Group AP-L) and in operated controls (Group AP-C). Every third day rats were offered a saccharin solution and immediately afterward were injected intravenously with 0.05 ml isotonic CuSO4. A group of pseudo-conditioned rats (Group SAC-C) was injected with CuSO4 approximately 24 h after ingestion of saccharin. Compared to controls animals, rats with area postrema damage acquired significantly weaker aversions to saccharin when it was paired repeatedly with intravenous CuSO4. After three conditioning trials, the rats in Group AP-L that were most resistant to acquisition of a taste aversion (Group AP-L) were again offered saccharin, but ingestion in this case was followed immediately by intragastric injection of CuSO4. After a single conditioning trial rats in Group AP-L demonstrated a robust aversion. The results are discussed in terms of the parallels in afferent systems between emetic physiology and some instances of taste aversion conditioning.

Afferent Pathways↗
PubMed1981

Relation of consummatory responses and preabsorptive insulin release to palatability and learned taste aversions.

The oral stimulation arising from food in the mouth produces a stereotyped sequence of ingestive consummatory responses in rats and a rapid release of insulin prior to the absorption of nutrients into the blood. Conversely, when noxious taste stimuli are infused into the mouth, a different, aversive set of consummatory responses is evoked, and no insulin is released. These experiments demonstrate that pairing a sapid taste solution with LiCl suffices to reverse the consummatory response sequence to subsequent presentations of that taste from ingestion to aversion and to abolish the preabsorptive release of insulin to that taste. This indicates an experience-produced shift in the palatability of the taste. It was further shown that a palatable but categorically noncaloric taste elicits behavioral ingestion but no insulin release, and it is concluded that separate but related control systems operate to produce consummatory behavior and ingestive neuroendocrine responses.

Animals↗
PubMed1980

The nucleus of the solitary tract in the monkey: projections to the thalamus and brain stem nuclei.

The projections of the nucleus of the solitary tract (NST) were studied by autoradiographic anterograde fiber-tracing and horseradish peroxidase (HRP) retrograde cell-labeling. Tritiated proline and leucine were deposited in electrophysiologically identified regions of NST. Injections of NST at levels caudal to where the vagus enters the nucleus, from which responses were evoked by stimulation of cranial nerves IX and X, revealed topographically organized bilateral projections to, most prominently, the ventrolateral medullary reticular formation which contains neurons of the ambiguus complex, and to the lateral and medial parabrachial nuclei, including a small portion of the medially adjacent central gray substance. Labeled fibers in the ventrolateral reticular formation were present from the nucleus retroambigualis rostralward to the retrofacial nucleus, with the densest concentration located over the nucleus ambiguus proper. The parabrachial projection was confirmed using HRP and shown to originate from cells in the medial subdivision of NST. Due to the problem of fibers en passant, it was not possible to interpret conclusively the cell-labeling seen around the solitary tract after HRP injections made in the region of the nucleus ambiguus. Labeled fibers were also traced from caudal NST to the dorsal motor nucleus of the vagus, but their origin could not be determined with certainty. Other labeled axons, traced to circumscribed parts of the inferior olivary complex and via the contralateral medial lemniscus to VPL of the thalamus, were shown in HRP experiments to originate from the dorsal column nuclei rather than NST. No labeled fibers were traced into the spinal cord, nor were any cells labeled in NST after large HRP deposits in upper cervical segments. Isotope deposits at levels of NST rostral to the entrance of the vagus, from which responses were evoked by rapid stimulation of the tongue, revealed an ipsilateral projection which ascends as a component of the central tegmental tract to the parvicellular part of the ventral posteromedial thalamic nucleus (VPMpc). After small HRP deposits in VPMpc, labeled cells in NST were restricted to the rostral part of the lateral subdivision. No labeled axons were traced from rostral NST to the ambiguus complex or parabrachial area. Injections of 3H-amino acids at intermediate levels of NST resulted in fiber-labeling in VPMpc, the parabrachial area, and the ambiguus complex.

Animals↗
PubMed1980

Central origins of cranial nerve parasympathetic neurons in the rat.

The location of central neurons that contribute preganglionic parasympathetic axons to cranial nerves VII, IX, and X in rats has been identified using horseradish peroxidase (HRP) tracing methods. Collectively, these neurons form an uninterrupted dorsal column that extends over the entire length of the medulla. The cephalic end of this column turns ventrally with neurons scattered in the parvicellular reticular formation between the rostral pole of the nucleus of the solitary tract (NST) and the facial motor nucleus. Applying HRP crystals to the cut cervical vagus labels neurons in the classically defined dorsal motor nucleus. Rostrally, this distribution continues along the medial edge of NST, ending just caudal to neurons exiting in the lingual-tonsilar branch of IX. At the rostral pole of the NST and ventral to it, neurons occur that serve the lingual-tonsilar and tympanic branches of IX, as well as the chorda tympani and greater superficial petrosal (GSP) branches of VII. Central neurons of the chorda tympani and tympanic nerves spread ventrally from NST into a sparse but largely coextensive distribution in the reticular formation lateral to the ascending radiations of the facial motor nucleus. Immediately ventral to this distribution, a dense accumulation of GSP efferent neurons appears rostrolateral to the facial motor nucleus. Although they vary considerably in number and packing density, the neurons of the dorsal efferent column and those extending from it into the reticular formation have similar morphological characteristics. The somata are medium-sized, fusiform, or multipolar, but with usually no more than five or six major processes.

Animals↗
PubMed1980

A study of the auditory evoked magnetic field of the human brain.

Small but reproducible and consistent auditory evoked magnetic fields have been obtained for 6 male subjects. These fields exhibit features with a clear spatial symmetry which can be accounted for by assuming that their source consists of two vertically oriented neuronal complexes symmetrically located deep in the temporal lobes. This assignment, which is also consistent with the available electrical data, places the sources within the auditory cortex near the sylvian fissure. Our results suggest that auditory evoked magnetic fields may provide assistance in unravelling the source structure that produces the auditory evoked response, both electrical and magnetic.

Auditory Cortex↗
PubMed1979

An autoradiographic examination of the central distribution of the trigeminal, facial, glossopharyngeal, and vagal nerves in the monkey.

The central distributions of primary afferent axons in cranial nerves V, VII, IX, and X have been re-examined autoradiographically after 3H-proline injections into their peripheral ganglia. Fiber-labeling after subtotal injections of the trigeminal ganglion, besides confirming earlier classical descriptions, suggests that trigeminal fibers of the ophthalmic and mandibular (but not maxillary) branches enter the ventrolateral part of the nucleus of the solitary tract (NST). Injection of VII's geniculate ganglion labels fibers which both ascend and descend upon reaching NST. The ascending fibers distribute in a compact and circumscribed zone immediately dorsal to the spinal V nucleus as far rostral as the caudal pole of the principal trigeminal nucleus. The descending fibers distribute to the lateral NST rostral to the level at which X joins the solitary tract. For a short distance caudal to this level, sparse label is confined to a small part of lateral NST ventral to the solitary tract, which corresponds to the zone receiving direct trigeminal afferents. Fiber-labeling after injections of the ganglia of nerves IX and X suggest the following. Although, upon reaching NST, a few fibers of either IX or X ascend as far rostrally as had those of VII, both have a much larger descending component which distributes to more caudal levels of NST. Most of IX's axons appear to end in the lateral NST; only a few travel as far as the obex. Fibers of X, on the other hand, are abundant in the medial and commissural parts of NST. Moreover, only X appears to have a crossed projection in the commissural nucleus and caudal portion of the contralateral NST. A few fibers of vagal origin also appear to enter the area postrema. Whereas fibers of X appear to constitute the solitary tract, few if any fibers of VII or IX travel within that fascicle. A significant descending components of labeled fibers appears in the spinal V tract when the superior ganglion of either IX or X is injected. These fibers distribute mainly in the pars caudalis of the spinal V nucleus and, to a lesser degree, the cuneate nucleus.

Animals↗
PubMed1979

Cells of origin of motor axons in the subdiaphragmatic vagus of the rat.

The central cell groups that give rise to the motor axons that travel in the subdiaphragmatic vagus were re-examined in the rat by transecting the dorsal or ventral vagus near the stomach and incubating the nerve stump in crystalline horseradish peroxidase (HRP). An exceedingly large percentage of cells was labeled throughout the dorsal motor nucleus of the vagus (mX), with labeled cells extending even beyond the rostro-caudal limits of the nucleus usually assigned on the basis of cytoarchitecture alone. Different patterns of cell-labeling could be correlated with one or the other of the two vagal branches. Incubation of the ventral branch labeled cells only in the left mX, while incubation of the dorsal branch labeled cells on both sides, although more extensively on the right. HRP-positive somata were also observed bilaterally in the nucleus ambiguus (NA) after incubation of either branch of the subdiaphragmatic vagus; this finding is in contrast to previous accounts in which motor fibers from NA were considered to project only to cervical and thoracic structures. These results suggest that mX and NA are responsible for a substantial component of abdominal innervation in the rat.

Animals↗