bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efferent projections of the deep mesencephalic nucleus (pars medialis) in the rat
Authors: Veazey R. B. , Severin C. M. 
Published: January 2005

AbstractThe projections of the medial part of the deep mesencephalic nucleus (DMN) were traced by autoradiography and retrograde horseradish peroxidase (HRP) techniques. No ascending projections were observed from the medial part of the DMN; however, two groups of descending fibers were observed. One group crossed the midline and coursed to the caudal part of the red nucleus. At this point, these fibers divided into two distinct bundles. One bundle of fibers passed caudally to terminate in the contralateral pontine reticular nucleus, superior olive‐trapezoid body complex, gigantocellular nucleus, and upper cervical spinal cord. The other bundle entered the medial longitudinal fasciculus (MLF) and coursed through the pons and medulla without termination, to enter the cervical spinal cord where terminations were noted in the dorsal horn. The other group of fibers from the medial DMN descended through the ipsilateral pons and medulla, projecting to the pontine reticular nucleus, superior olive‐trapezoid body complex, gigantocellular nucleus, and upper cervical spinal cord. These findings indicate that the medial part of the DMN is likely to be involved in complex sensorimotor events via reticulobulbar and reticulospinal connections.
The nucleus of the solitary tract in the monkey: Projections to the thalamus and brain stem nuclei
Authors: Beckstead Robert M. , Morse Joel R. , Norgren Ralph 
Published: January 2005

AbstractThe 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 originiate 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.
Number and distribution of neurons in leech segmental ganglia
Authors: Macagno E. R. 
Published: January 2005

AbstractThe number of neurons and their distribution were determined for specific segmental ganglia from the nerve cord of four different species of leech. Quantitative data were obtained by using computer‐aided techniques for the analysis of nerve structure from serially sectioned or whole‐mounted tissue. The species studied were Hirudo medicinalis, Macrobdella decora, Haemopis marmorata (family Hirudinidae), and Haementeria ghilianii (family Glossophoniidae).Two sets of ganglia were studied in each species: middle ganglia (9, 10, and 11) and sex ganglia (5 and 6). The middle ganglia, as well as the rest of the 21 segmental ganglia, except 5 and 6, are thought to be quite similar. The sex ganglia are associated with the sexual organs and appear to have more neurons.The data reported here indicate that: a) the number of neurons in a specified ganglion varies by one to two percent from animal to animal of a given species; b) the middle ganglia of a particular leech each have approximately the same number of neurons, with a variation also within two percent; c) the middle ganglia of Hirudo, Macrobdella, and Haementeria have some 20 fewer (about 380); d) the sex ganglia of Hirudo, Macrobdella, and Haemopis have a few hundred more neurons than their middle ganglia, with the exact number varying according to the species, but the sex ganglia in Haementeria have only about 20 more neurons than their middle ganglia; e) the distribution of neuronal somata among glial packets is not symmetric about the midsaggital plane of the animal, and the number of somata in each packet is variable; and f) the geometry of the glial packets is generally invariant, but occasionally packets are found in abnormal positions.
Somatosensory thalamus of a prosimian primate (Galago senegalensis). II. An HRP and Golgi study of the ventral posterolateral nucleus (VPL)
Authors: Pearson J. C. , Haines D. E. 
Published: January 2005

AbstractThe topographic arrangement and cytoarchitecture of cells in the ventral posterolateral nucleus (VPL) of a prosimian primate (Galago senegalensis) were studied using horseradish peroxidase (HRP) and Golgi impregnation techniques. Following cortical implants of HRP, reactive neurons in VPL are organized into medially concave lamellae which extend through the dorsoventral and rostrocaudal dimensions of the nucleus. After implant in forelimb and hindlimb areas of motor‐sensory cortex, labeled cells are confined to the medial (VPLm) and lateral (VPLl) portions of VPL, respectively. HRP‐positive cells in the ventral part of each lamella are organized into clusters which correspond to the clusters of cells and “parcellated‐bursts” of preterminal debris previously described in bushbaby VPL (Pearson and Haines, this volume). HRP‐reactive cells in the ventral intermediate nucleus (Vim) are evenly distributed as contrasted to the tightly clustered groups of somata in the adjacent VPL. This evidence argues in favor of the presence of Vim in dorsal thalamus of this prosimian.Golgi impregnations reveal two main types of relay cells in Galago VPL. Type I cells have multiangular somata, straight distal dendrites, and primary dendritic branch points which are free of appendages. Type II cells have rounded somata, sinuous distal dendrites, and clusters of appendages located at primary branch points. Intermediate cells (i.e., cells with morphological features in between types I and II) are also present in VPL. Comparison of tufted Golgi impregnated cells with neurons labeled with HRP shows definite similarities in somata size and shape, and in the orientation of proximal dendrites. This evidence corroborates the relay nature of the tufted neurons in VPL. Relay cells in Galago VPL have morphological features which are similar to those of relay cells in lateral and medial geniculate nuclei of cat and primate.Type III cells have small round somata, radiate dendrites with elaborate appendages, and axons which appear to be intrinsic to VPL. Consequently, these cells are considered to be interneurons in the VPL of Galago. Glial‐like neurons (type IV cells) were also observed. These have beaded dendritic processes similar to those which presumably represent presynaptic boutons in other species. Consequently, these cells are also assumed to function intrinsically within VPL.
Physiological development of a monosynaptic connection involved in an adult insect behavior
Authors: Heathcote R. David 
Published: January 2005

AbstractLocust flight is an exclusively adult behavior whose neural basis has been extensively studied. The coordinated neural pattern underlying this behavior appears rapidly at the end of postembryonic development. This paper examines the ontogeny of elements of the nervous system involved in the behavior. Alternative extreme hypotheses are: (1) the neurons and synapses involved develop concomitant with the behavior, or (2) they are constructed early in development, and are activated at the appropriate time by, for example, the release of inhibition. These hypotheses were evaluated by selecting a synapse that is important in adult flight, and monitoring its physiological features during postembryonic development.The synapse between the forewing Stretch Receptor (SR) and the First Basalar (BA) motor neuron, two uniquely identified neurons, mediates a monosynaptic reflex which operates only in flight. The EPSP, initiated by SR in BA, was recorded intracellularly during the last four of six postembryonic instars. As early as third instar, the monosynaptic EPSP is present and appears to be as effective as in the adult. It also decrements and summates similarly in younger animals and adults. Therefore, some flight system synapses are present and effective throughout most of postembryonic development, and thus do not develop concomitant with the behavior.
Two‐dimensional maps of the cerebral cortex
Authors: van Essen D. C. , Maunsell J. H. R. 
Published: January 2005

AbstractA procedure is described for constructing two‐dimensional, unfolded representations of the cerebral cortex. The technique is based on information contained in outlines of histological sections, and it allows an entire hemisphere to be represented on a single cortical map. Maps for different hemispheres from individuals of the same species are similar in size, shape, and organization, and their configuration is largely independent of the plane of sectioning used for reconstruction. Many types of information pertaining to the location and organization of different functional subdivisions can be displayed on cortical maps; representative applications of the technique to mapping cerebral cortex in the macaque and the cat are shown. Areal measurements on cortical maps correspond closely (generally within 20%) to actual surface areas in the intact hemisphere. Therefore, the maps can also be used to provide accurate determinations of the absolute and relative extent of various anatomical and functional subdivisions of the cortex.
Development of the human cervical spinal cord with reference to synapse formation in the motro nucleus
Authors: Okado Nobuo 
Published: January 2005

AbstractSynaptic development in the motor neuropil of the cervical spinal cord was quantitatively studied by light and electron microscopy in human embryos and fetuses ranging from five to 19 weeks of ovulation age. The numbers of axodendritic synapses increase substantially at the end of the eighth week. However, axosomatic synapses rapidly proliferate between 10.5 and 13 weeks of ovulation age. The increases in both types of synapses generally coincide with the behavioral chages in human fetuses that have been reported by other investigators. Only synaptic boutons containing spherical vesicles (S‐type synapses) were found in the motor neuropil throughout the stages examined; no synapses with flattened vesicles (F‐type synapses) were encountered. The majority of these synaptic boutons contain only a small number of synaptic vesicles (fewer than 20), although the number tends to increase with maturation. There is no significant maturational change in the size of synaptic vesicles. The present study suggests that synapse formation in the motor neuropil of the human fetus cervical spinal cord may continue up to 19 weeks of ovulation age because immature types of synapse are found in all fetuses. Myelin formation probably begins by the 11th week.
Naturally occurring alterations of cortical layers surrounding the fissura prima of rat cerebellum
Authors: Griffin W. S. T. , Eriksson M. A. E. , Del Cerro M. , Woodward D. J. , Stampfer N. 
Published: January 2005

AbstractWe have regularly observed alterations in the three‐layered arrangement of cerebellar cortex surrounding fissura prima in normal adult and neonatal rats. In 90 of 110 rat brains analyzed, the cortical layers surrounding fissura prima were found to be altered from the four‐layered (neonatal) or three‐layered (adult) arrangement found in the majority of the remainder of cerebellar cortex. This common alteration extended long distances (as much as 320 microns) on either side of the midline, causing fissura prima to become more and more shallow from its lateral to medial extent. In sagittal sections at the lateral edge of the alteration in neonatal cerebellum, the external granular layer and pial cells disappeared, leaving an expanse of molecular layer lying between internal granular layer cells of lobules V and VI. Proceeding medially toward the midsagittal region, the cells of the internal granular layer of lobules V and VI were situated closer together and often merged. In such sections Purkinje cells did not usually remain in a monolayer, but were displaced, and clusters of these cells were sometimes found within the white matter. Various complex configurations of internal granular layer, molecular layer, and Purkinje cell groups surrounding fissura prima were commonplace in regions of cerebellum as far lateral as 320 microns on either side of the midsagittal plane. The greatest dorsoventral extent of such alterations measured was 400 microns. The presence of these previously unreported deviations is unrelated to experimental stress, as they occur spontaneously, possibly due to a vestigeal disorganization left in midline zones after early cell migration phases.
Segmental organization of sympathetic preganglionic neurons in the mammalian spinal cord
Authors: Rubin Eric , Purves Dale 
Published: January 2005

AbstractWe have used retrograde transport of horseradish peroxidase to determine the distribution of the preganglionic cell bodies whose axons join particular rami of the thoracic spinal cord in a series of guinea pigs, and in a small number of hamsters and cats. In contrast to other recent studies, our results show that the neurons sending axons to a ramus are confined to a single segment at the corresponding spinal level. This segmental organization supports the idea that the rostro‐caudal position of preganglionic cell bodies is one determinant of selective synapse formation between preganglionic axons and sympathetic ganglion cells.
Correlation between soma size and dendritic morphology in cat retinal ganglion cells: Evidence of further variation in the γ‐cell class
Authors: Stone Jonathan , Clarke Rosemary 
Published: January 2005

AbstractThe morphology of ganglion cells in the cat's retina has been examined in Golgi‐impregnated whole mounts. The α‐, β, and γ‐cell groups described by Boycott and Wässle ('74) were observed. Also observed were may cells with wide dendritic fields typical of γ‐cells, and medium‐sized somas more usually associated with β‐cells. It is suggested that these cells belong to the γ‐cells group, adding to the variety already described by Boycott and Wässle among γ‐cells.
Distribution of small and medium‐sized ganglion cells in the cat's retina
Authors: Stone Jonathan , Keens Jeremy 
Published: January 2005

AbstractThe distributions of small and medium‐sized ganglion cells in the cat's retina have been studied.The soma size ranges of ganglion cells projecting to the superior colliculus and the A‐laminae of the dorsal lateral geniculate nucleus were determined by the retrograde transport of horseradish peroxidase. Confirming previous work, the results suggest a division of the overall soma population into large, medium and small ranges. The large somas are the cell bodies of α‐ or Y‐cells; the small somas are the cell bodies of γ‐ or W‐cells, most of which project to the superior colliculus; and the medium‐sized somas include the cell bodies of β‐ or X‐cells and of γ‐ or W‐cells, most of which project to the forebrain.The small‐soma (collicular‐projecting) cells have a strongly streaky distribution, i.e., the isodensity lines in a map of their distribution are markedly elongated horizontally. These cells form the principal component of the visual streak, especially in nasal retina. The medium‐soma (forebrain‐projecting) cells also show some streakiness, i.e., their isodensity lines are also elongated horizontally, but less markedly than for small cells. The results also show differences between nasal and temporal retina in the distributions of medium‐sized and small somas.It is suggested that the patterns of distribution of small and medium cells may be reflected in the topography of visual centres of the midbrain and forebrain, respectively.
Patterns of cortico‐cortical connections related to tonotopic maps in cat auditory cortex
Authors: Imig Thomas J. , Reale Richard A. 
Published: January 2005

AbstractTopographic distributions of cortico‐cortical projections from the primary (AI), anterior (A), posterior (P), ventroposterior (VP), and second (AII) auditory fields were studied in relation to tonotopic maps in combined anatomical and electrophysiological experiments. Distributions of axon terminals were determined by autoradiographic labeling with tritiated proline and leucine. Each of fields A, AI, P, and VP is connected with the other three in the same hemisphere as well as with a number of other auditory cortical areas. Additionally, neurons in each of the fields studied were found to project to the lateral bank of the collateral fissure. In general, regions near the injection site receive more densely labeled projections than do more distant targets. Neurons in each field were found to project to one or more areas in the opposite hemisphere. Only similar portions of the best‐frequency representations in fields A, AI, P, and VP are interconnected. A single isotope injection generally produced multiple patches of labeling within each of several cortical fields. Within AI, projections from contralateral fields A and AI and from ipsilateral fields A and P terminate in patches which are often elongated in a direction parallel to the low‐to‐high best‐frequency gradient. A divergence in the projections from one field upon another is apparent in many experiments. Within fields A, AI, P, and VP, patches of label are distributed along a band of cortex oriented parallel to isofrequency lines.
Lumbosacral predominance of vestibulospinal fibre projection in the rat
Authors: Shamboul K. M. 
Published: January 2005

AbstractThe somatotopic organization of the vestibulospinal tract (VST) and the percentages of cells of the lateral vestibular nucleus (LVN) contributing fibres to different regions of the spinal cord of the rat have not been studied before. These problems are investigated using the technique of retrograde cellular degeneration. Varying degrees of spinal cordotomies were performed at upper cervical, thoracic, and lumbar segments in 75 adult rats of Wistar strain. The animals were killed after varying survival periods and the brain stems were processed in the usual way. Chromatolytic neurons were observed in the ipsilateral lateral vestibular nucleus, and no such neurons were seen contralaterally. Following lumbar lesions, reacting neurons were condensed in the caudal two thirds, while with cervical and thoracic lesions, such neurons occupied more cranial levels in the nucleus. It is concluded that vestibulospinal fibres projecting to lumbosacral segments arise from the caudal two thirds of the nucleus, while those projecting to cervical and thoracic segments come from the cranial two thirds, those to the cervicals arise from the most cranial levels. The dense lumbosacral projection was attributed to the role played by the vestibulospinal fibres in maintaining extensor tonus of antigravity musculature, especially in the rat, which can effectively stand on its hindlimbs and use its free forelimbs for handling and examining objects.
Representations of the body surface in postcentral parietal cortex of Macaca fascicularis
Authors: Nelson R. J. , Sur M. , Felleman D. J. , Kaas J. H. 
Published: January 2005

AbstractThe somatotopic organization of the postcentral parietal cortex of the Old World monkey, Macaca fascicularis, was determined with multi‐unit microelectrode recordings. The results lead to the following conclusions: (1) There are at least two complete and systematic representations of the contralateral body surface in the cortex of the postcentral gyrus. One representation is contained within Area 3b, the other within Area 1. (2) While there are important differences in the organization of the two representations, they are basically mirror‐images of each other. (3) Each representation maintains body‐surface adjacency by cortical adjacency in some mediolateral regions. In other regions, two types of discontinuities can be described: first, in which adjacent body surfaces are represented in separate cortical loci; second, in which adjacent cortical regions represent disparate body‐surface regions. The internal organization of each representation is better described as a composite of somatotopic regions (Merzenich et al., '78) than as a serial array of dermatomal bands, or as a “homunculus.” (4) While architectonic Area 2 responds to stimulation of deep body tissue, at least parts of Area 2 also respond to cutaneous stimulation. The organization of the cutaneous representation of the hand in Area 2 is basically a mirror‐image of the hand representation in Area 1. (5) Area 3a is activated by deep body tissue stimulation, suggesting the possibility of a fourth body representation within the traditional “S‐I” region of somatosensory cortex in macaques. In accord with a previous study in a New World monkey (Merzenich et al., '78), we suggest that the cutaneous representation in Area 3b be considered as SI proper, and that the cutaneous representation in Area 1 be termed the posterior cutaneous field. Furthermore, based on the orientation of the representations of the body surface, as well as other factors, we suggest that the representation in Area 3b is homologous to “SmI” (or “SI”) in non‐primates.