Projection fibers from the main sensory trigeminal nucleus and the supratrigeminal region
TL;DR: Fiber projections from the main sensory trigeminal nucleus and the supratrigeminal region in the cat and monkey have been studied by the Nauta, Fink‐Heimer and Marchi methods.
Abstract: Fiber projections from the main sensory trigeminal nucleus and the supratrigeminal region (reticular formation dorsal and rostrodorsal to the motor trigeminal nucleus) in the cat and monkey have been studied by the Nauta, Fink-Heimer and Marchi methods.
Following experimental lesions in the main sensory trigeminal nucleus and its vicinity, the crossed ventral and the uncrossed dorsal trigeminal tracts were traced rostrally to the posteromedial ventral nucleus of the thalamus. The uncrossed dorsal trigeminal tract ascended through Forel's tegmental fascicle (tractus fasciculorum tegmenti Foreli). However, Forel's tegmental fascicle was composed mainly of the ascending reticular fibers terminating in the intralaminar nuclei of the thalamus and in the subthalamus. Commissural components distributing chidfly to the motor trigeminal nucleus of the opposite side appeared to arise from the supratrigeminal region as well as from the main sensory trigeminal nucleus. A fiber bundle, arising from the reticular zones surrounding the motor trigeminal nucleus, descended through the lateral reticular formation immediately ventromedial to the spinal trigeminal nucleus down to lower levels of the medulla oblongata.
The functional significance of the supratrigeminal region as an interneuron system intercalated between the trigeminal sensory and the cranial motor systems is discussed.
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TL;DR: By means of a combination of electrophysiological and anatomical procedures, the projections of the anterior portion of the solitary nucleus were traced to the parabrachial nuclei in the pons, structures hitherto not considered to be included in the taste pathway.
Abstract: By means of a combination of electrophysiological and anatomical procedures, the projections of the anterior portion of the solitary nucleus were traced to the parabrachial nuclei in the pons, structures hitherto not considered to be included in the taste pathway. Responses to taste stimuli were recorded from this pontine area. Lesions in the pontine taste area resulted in degeneration of fibers reaching the lingual area in the thalamus.
263 citations
TL;DR: Projections to the lateral diencephalon from the dorsal column nuclei, lateral cervical n, and spinal cord in cats and monkeys, and from the spinal portion of the trigeminal n in the cat were compared using a double‐orthograde labeling strategy.
Abstract: Projections to the lateral diencephalon from the dorsal column nuclei (DCN), lateral cervical n. (LCN), and spinal cord (ST) in cats and monkeys, and from the spinal portion of the trigeminal n. (sTN) in the cat were compared using a double-orthograde labeling strategy. This strategy combines autoradiographic and degeneration tracing methods in the same animal and permits direct comparisons of the terminal labeling patterns of two different pathways in each experiment.
The results suggest that the major part of the lateral diencephalon which receives input from the somatic sensory pathways in both the cat and the monkey is arranged in a core-shell fashion. The core consists of the group of nuclei which together constitute the ventrobasal complex (VB). The shell consists of a group of nuclei which together tend to surround VB nearly completely. This group includes the posterior group (PO), the ventral posteroinferior n. (VPI), and the border region between VB and the ventrolateral n. (VB-VL). In addition to the core and shell regions, two other regions in the lateral diencephalon receive input from the somatic sensory pathways. These regions are the ventromedial part of the magnocellular portion of the medial geniculate n. (MGNm) and caudomedial portion of the zona incerta (ZI).
The cytoarchitectural and hodological patterns of the core region differ from those of the shell region. In both the monkey and the cat, the core region (VB) has a relatively homogeneous cytoarchitectural appearance and is filled by dense inputs from DCN, LCN, and sTN in the cat and from DCN, LCN, and ST (and probably from sTN) in the monkey. Direct comparisons of the terminals of fibers from different pathways demonstrate that although there is some convergence on the same neurons within VB, the major tendency is for each of the inputs to form its densest terminations on different neurons. This partial segregation manifests itself in two ways. First, each pathway has its own preferred territory within VB where its terminations are the densest. Second, the terminal fields of the inputs usually have a clustered appearance which is characterized by dense patches of terminals separated by regions in which the terminations appear quite sparse. The dense patches from different pathways do not occur in relation to the same groups of neurons.
In contrast, most portions of the shell region have a lower cell density than that of the core and a heterogeneous cytoarchitectonic appearance which can often be described as transitional in character between its neighboring areas. In both species, different parts of the shell region receive sparse and scattered input from those pathways which project densely and precisely to areas immediately adjacent to that part of the shell. Very few of the terminals of these different inputs appear to converge on the same groups of neurons.
The two otehr recipient targets of somatic senory input (i.e., MGNm, ZI) each has its own characteristic connective pattern that differs from taht of either the core or the shell region.
The connective patterns in the cat and monkey are quite similar. The mian differences are in the projections of parts of the ST ans LCN pathways. The nature of these differences suggest taht it might be useful from a functional perspective to consider the LCN and ST pathways together as part of the same spinal system, rather than as separate functional entities. The LCN pathyway could then be viewed as having perhaps been dervied from different parts of a single population of diencephalic-projecting neurons in the spinal cord of the two species.
When these anatomical results are considered together with the available electrophysiological evidence, it appears that the response properties and functions of some portions of the somatic senory regions within the diencephalon can be generally predicted from knowledge of the particular pathways whose axons terminate within these regions. Such predictions can be made, however, only when the input pathways have markedly different functions (e.g., vestibular, auditory, cutaneous). At present, more precise kinds of predicitions are precluded by the similarity that exists between the functional properties of many of the units in teh DCN, sTN, LCN, and ST pathways, and the luck of knowledge of the sorting processes which occur as fibers in each of these pathways diverge to terminate in different parts of the brain.
261 citations
TL;DR: The sections in this article are: Neuroanatomy of Masticatory System, General Conclusions, and Role of Sensorimotor Cortex in Mastication and Voluntary Jaw Movements.
Abstract: The sections in this article are:
1
General Features of Mandibular Motor System
1.1
Muscles of Mandible
1.2
Summary Neuroanatomy of Masticatory System
2
Mastication
2.1
Characteristics of Normal Mastication
2.2
Reflexes Possibly Involved with Chewing
2.3
Evidence Concerning Contribution of Jaw Reflexes to Mastication
2.4
Subcortical Mastication Pattern Generator
3
Initiation and Control of Mandibular Movements
3.1
Role of Sensorimotor Cortex in Mastication and Voluntary Jaw Movements
3.2
Peripheral Systems and Voluntary Isometric Jaw Muscle Contraction
3.3
Trigeminal Relationships in Cerebellum
4
Summary of General Conclusions
192 citations
TL;DR: The projections of the locus coeruleus and adjacent pontine tegmentum have been studied using anatomical and physiological methods in the cat and fibers could not be consistently traced to the cerebral cortex, and were not seen at all in the cerebellum.
Abstract: The projections of the locus coeruleus and adjacent pontine tegmentum have been studied using anatomical and physiological methods in the cat. Axonal trajectories were traced using either the Fink-Heimer I method following electrolytic lesions, or the autoradiographic method after injection of tritiated proline into the nucleus. Results with both methods were similar. Axons of locus coeruleus neurons ascended ipsilaterally through the mesencephalon lateral to the medial longitudinal fasciculus, ventrolateral to the central gray. In the caudal diencephalon, the ascending fibers entered the centrum medianum-parafascicular complex where they diverged into two fascicles; a dorsal fascicle which terminated in the intralaminar nuclei of the thalamus, and a ventral fascicle which gave off fibers to the ventrobasal complex and reticular nucleus of the thalamus while continuing ventrolaterally into the lateral hypothalamus medial to the internal capsule. Fibers of the ventral fascicle ascended in the lateral hypothalamus and zona incerta and were traced through the preoptic region into the septum. Fibers could not be consistently traced to the cerebral cortex, and were not seen at all in the cerebellum.
Throughout the ascending course of the path from the locus coeruleus, axons were given off to the pretectal area, the medial and lateral geniculate nuclei, and the amygdala; fibers passed contralaterally through the posterior commissure, the midline thalamus, and the supraoptic commissure. Fibers descending from the locus coeruleus surrounded the intramedullary portion of the facial nerve and further caudally were observed ventrolateral to the hypoglossal and dorsal vagal nuclei.
The axonal trajectories visualized with degeneration and autoradiographic methods followed closely those previously shown for reticular formation neurons, but were also similar to locus coeruleus projections revealed by histofluorescence methods. After injections of horseradish peroxidase into the centrum medianum-parafascicular complex, lateral hypothalamus or preoptic region, labeled neurons were located in the locus coeruleus, nucleus subcoeruleus, and lateral parabrachial nucleus. Reticular formation neurons were not labeled. Neurons in locus coeruleus and adjacent pontine tegmentum could be antidromically activated by stimulation in the rostral midbrain or caudal diencephalon.
Our data indicate that both adrenergic and non-adrenergic neurons of the dorsolateral pontine tegmentum have similar projections.
186 citations
TL;DR: It was investigated in cats whether monosynaptic projections from lumbosacral neurons to the M‐region indeed exist, and it was demonstrated that the lateral part of the periaqueductal gray contains neurons projecting to theM‐region.
Abstract: Information concerning the rate of bladder filling is determined by receptors in the bladder wall and conveyed via afferent fibers in the pelvic nerve to sensory neurons in the lumbosacral cord. It was assumed that this information is relayed from the lumbosacral cord to a medial cell group in the dorsolateral pontine tegmentum, called the M-region, the pontine micturition center, or Barrington's nucleus. The M-region, in turn, projects via long descending pathways to the sacral parasympathetic motoneurons. In the present electron microscopic study, it was investigated in cats whether monosynaptic projections from lumbosacral neurons to the M-region indeed exist. Wheat-germ agglutinin-horseradish peroxidase injections were made into the lumbosacral, cord. Many retrogradely labeled dendrites and somata were found in the M-region, but no labeled terminals were found on retrogradely labeled dendrites or somata. Only a small number of anterogradely labeled terminals, which were filled with mainly round vesicles, contacted unlabeled dendrites in the M-region. In contrast, many more anterogradely labeled terminals, which were filled with mainly round and, to a limited extent, dense core vesicles and with asymmetrical synapses, were found on dendrites in the lateral part of the periaqueductal gray (PAG). Previously (Blok and Holstege [1994] Neurosci. Lett. 166:93-96), it was demonstrated that the lateral part of the FAG contains neurons projecting to the M-region. A concept for the central organization of the micturition reflex is presented in which ascending projections from the lumbosacral cord convey information on bladder filling to the FAG. When the bladder contains so much urine that voiding is necessary, the FAG, in turn, triggers the M-region. The M-region, however, also receives afferents from the preoptic area, which might be involved in the final decision to start micturition. (C) 1995 Wiley-Liss, Inc.
185 citations
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TL;DR: The original, non-suppressive Natua method for impregenation of terminal degeneration has been modified by the introduction of a potassium permanganate-uranyl nitrate sequence, resulting in a selective impregnation of degenarated axons inclusive of their synaptic thickenings.
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Book•
01 Jan 1987
TL;DR: There are excellent regional atlases for both the cat and the monkey, but these are the first to cover the brain stem and basal telenccphalon in such a complete fashion and should prove of particular value to people working in the caudal brain stem.
Abstract: Stereotaxic Atlas of the Monkey Brain. By Ray S. Snider and John C. Lee. Price, $12.50 (each). Illustrated, University of Chicago Press, 5750 Ellis Ave., Chicago 37, 1962. These hard-cover atlases consist of photographs of Nissl and Weil sections at 0.5 mm. intervals. There are no line drawings or outlining of structures, but the quality of the staining and photographs is excellent and all structures are easily recognized. If one desires more precise delineation of such things as the thalamic nuclei or the subdivisions of the amygdala, he should be prepared to obtain this information by a study of his own slides and reference to research articles on the region in question. Measurements obtained from a large number of brains were utilized in establishing the criteria for the "normal" brain. In addition, the Weil and Nissl sections at each level were taken from two different animals to give some indication of the average range of variability. The tissue was cut at 40\g=m\by frozen section technique to assure minimal shrinkage. The cat sections were photographed at \m=x\13 magnification and extend from A19.5 to P11.0. The height and width of the sections are sufficient to include most of the structures one would want to reach by stereotaxic means. The rostral sections cover the region from just above the corpus callosum to the bottom of the brain. Some sections extend as far as 16.5 mm. lateral to the midline; the entire hippocampus, amygdala, and pyriform cortex arc shown. Enough of the cerebellum is included with the caudal brain stem to show the deep cerebellar nuclei. The monkey (Macaca mulatta) sections were photographed at X9 magnification and extend from A20.0 to P10.0. Despite the lower magnification, these cross-sections arc not as complete in extent as in the cat because of the larger size of the monkey brain. Nevertheless, most of the frequently sought structures are shown, and anything outside the scope of the photograph could be easily extrapolated by reference to actual sections. In summary, these two atlases admirably fulfill a long-standing need ; there are excellent regional atlases for both the cat and the monkey, but these are the first to cover the brain stem and basal telenccphalon in such a complete fashion. For this reason they should prove of particular value to people working in the caudal brain stem. W. D. Hagamen, M.D.
1,369 citations
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