bluuebunny/crossref_metadata_2025_split huggingface dataset:
Projections from the amygdaloid complex to the cerebral cortex and thalamus in the rat and cat
Authors: Krettek J. E. , Price J. L. 
Published: December 2004

AbstractProjections asre described from the basolateral, lateral and anterior cortical nuclei of the amygdaloid complex, and from the prepiriform cortex, to several discrete areas of the cerebral cortex in the rat and cat and to th mediodorsasl thalamic nucleus in the rat. These projections are very well‐defined in their origin, and in their area and laminar pattern of termination.The basolateral amygdaloid nucleus can be divided into anterior and posterior divisions, based on cytoarchitectonic and connectional distinctions. In both the rat and cat the posterior division projects to the prelimbic area (area32) and the infralimbic area (area 25) on the medial surface of the hemisphere. The anterior division projects more lightly to these areas, but also sends fibers to the dorsal and posterior agrangular insular areas and the perirhinal area on the lateral surface. Furtheremore, in the cat the perirhinal area is divided into two areas(area 35 and 36) and the anterior division projects to both of these and also to a ventral part of the grangular insular area; this last area is adjacent to, but separate from the auditory insular area and the second cortical taste area. In most of these areas, the fibers from the basolateral nucleus terminate predominantly in two bands: one in the deep part of layer I and layer II, and a heavier band in layer V (in the rat) or layers V and VI (in the cat).The lateral amygdaloid nucleus projects heavily to the perirhinal area, and also to the posterior agranular insular area. These fibers terminate predominantly in the midle layers of the cortex, although the cellular lamination in these two areas is relatively indistinct. The anterior cortical amygdaloid nucleus and the prepiriform cortex both project to th infralimbic area and the ventral agranular insular area, and the anterior cortical nucleus also projects to the posterior agranular area and the perirhinal area. In all of these areas, the fibers from these olfactory‐relasted structures terminate in the middle of layer I.In the rat, the two divisions of the basolateral nucleus also project to the medial segment of the mediodorsasl thalamic nucleus, with the anterior division projecting mainly to the posterior part of this segment and the posterior division to the anterior part. The endopiriform nucleus, deep to the prepiriform cortex, projects to the central segment of the mediodorsasl nucleus, since little or no projection could be demonstrated from the prepiriform cortex itself. Projections to the mediodorsal nucleus have not been found in the cat.
Unmyelinated and small myelinated axons in rat ventral roots
Authors: Coggeshall Richard E. , Emery Dennis G. , Ito Haruhide , Maynard Christine W. 
Published: December 2004

AbstractThe present study is an analysis of the ventral roots in the rat. The smallest myelinated fibers are found in segments T1‐L2 and L6‐S1. These fibers are regarded as preganglionic efferents and the L6‐S1 outflow is more cranial than the sacral parasympathetic outflow in other animals. Large numbers of unmyelinated axons are seen in segments T1‐L2 and L6‐S1, the same segments that contain the smallest myelinated fibers. This data will be used as a baseline for determining the functional categories of the unmyelinated axons.
Retinotectal projection of the adult winter flounder (Pseudopleuronectes americanus)
Authors: Luckenbill‐Edds L. , Sharma S. C. 
Published: December 2004

AbstractThe winter flounder shifts the orientation of its body 900 at metamorphosis so that its left side is functionally ventral and its right side functionally dorsal. Concomitantly the left eye migrates onto the right side. The net result of these complex metamorphic changes is that the dorsoventral axes of the visual fields are perpendicular to the body rather than parallel as in most other teleosts. The developing faltfish may provide a resource for studying the formation of neural connections, for the change in orientation may necessitate some shift in connections in visumotor pathways. As a baseline for developmental studies, we have established the retinotectal projection in adult winter flounder by means of anatomical tracing techniques (autoradiography and degeneration staining) and electrophysiological mapping techniques. The histological pattern of retinal afferents to the tectum is similar to that of other teleosts; afferents are confined to the superficial white and gray zone, with a few fibers coursing in the deep white zone. Electrophysiological mapping shows that the visuotectal projection is complete over the entire extent of the tectum, symmetrical for right and left fields and patterned normally.
Descending inputs to octopus cell area of the cat cochlear nucleus: An electron microscopic study
Authors: Kane Eileen S. 
Published: December 2004

AbstractLarge, unilateral lesions of the superior olivary complex (SOC) were made in 18 adult cats. Terminal degeneration was studied electron microscopically in the octopus cell area (OCA) of the caudal cochlear nuclei both ipsilateral and contralateral to lesions, after 1 to 14 postoperative days. Three synaptic types (OCA types 1, 2, and 3) have been previously described upon octopus cell somas and dendrites and types 1 and 2 identified as cochlear in origin. The present study shows a new synasptic ending (OCA type 4) on small octopus cell dendrites as well as dendrodentritic contacts. Following SOC ablations, type 4 endings degenerated in the OCA ipsilateral to the lesion. In the OCA contralateral to the same lesion, however, degeneration was found in type 3 terminals ending upon more proximal octopus cell dendrites and upon somas. Ipsilateral terminal degeneration occured between two and four postoperative days, was rere by seven days, and was gone by 14 days after these lesions. However, contralateral terminal degenaration was rare until four days, was most abundant after seven days, and was still present after 14 postoperative days. The different synaptic types and time courses of degeneration in the ipsilateral versus the contralateral OCA, suggested that type 4 endings originate from an ipsilateral source, ssuch as the lesioned periolivary region, while type 3 endings originate either from the contralateral SOC or from higher contralateral nuclei. Other evidence for these sources and possible functions of these descending inputs asre briefly discussed.
The organization of the pulvinar in the grey squirrel (Sciurus carolinensis). II. Synaptic organization and comparisons with the dorsal lateral geniculate nucleus
Authors: Robson J. A. , Hall W. C. 
Published: December 2004

AbstractThe purpose of these experiments was to compare the synaptic organization of the subdivisions of the pulvinar defined in the preceding paper (Robson and Hall, '77) with each other and with the organization present in the dorsal lateral geniculate nucleus. The electron microscope was used to analyze normal synaptic arrangements and degenerating axonal terminals resulting from lesions. The dorsal lateral geniculate nucleus in the grey squirrel contains synaptic clusters similar to those described previously for other species. These clusters are characterized by large optic tract terminals which form multiple contacts onto large dendritic processes and other processes containing flat or pleomorphic vesicles. The geniculate lamina adjacent to the optic tract receives projections from the superior colliculus as well are from the retina. The terminals of the superior colliculus axons are small and medium sized and lie outside of the synaptic clusters. The retinal terminals are in the clusters. In the pulvinar, the rostro‐medial subdivision contains synaptic clusters which resemble those in the lateral geniculate nucleus. These clusters contain large axon terminals which make multiple contacts onto large dendrites. However, these terminals are not contributed by an ascending sensory pathway but by axons from strait cortex. The rostro‐lateral and caudal subdivisions of the pulvinar also contain synaptic clusters, but these clusters consist of a segment of a large dendrite which is ensheathed by medium‐sized terminals. Since only a few of these medium sized terminals in any one cluster degenerate after tectal lesions, and none degenerate after cortical lesions, it is suggested that the morphological arrangement of these clusters may permit the convergence of axons from several sources, some of which are unidentified, onto the same dendritic segment.
Corticocortical fiber connections of the rabbit visual cortex: A fiber degeneration study
Authors: Towns Lex C. , Giolli Roland A. , Haste David A. 
Published: December 2004

AbstractCorticocortical fiber projections of the striate and occipital cortex of the rabbit, as defined by Rose ('31) have been determined by fiber degeneration methods following the production of cortical lesions within each of 24 rabbits. We have assumed that the striate and occipital cortices correspond respectively to the visual cortical areas 1 and 2 (V1 and V2) which have been demarcated electrophysiologically by Thornpson et al. ('50).A study of the ipsilateral fiber projections of the striate and occipital cortex of the rabbit reveals three distinct sets of associational corticocortical connections.(1) Neurons located in layers I‐III of all regions of the striate cortex and the occipital cortex send fibers to terminate predominantly in layer V, but also in layers IV and VI, immediately beneath the cells of origin; however, the cells in the supragranular layers have not been found to send fibers to any other region of cerebral cortex. (2) The binocular portions of V1 and V2 appear to be interconnected ipsilaterally since cells in layers IV‐VI of the lateral striate cortex have been shown to project to all layers of a restricted, adjacent portion of the medial occipital cortex; and the cells in layers TV‐VIof medial occipital cortex send a similar, restricted projection to the adjacent lateral striate cortex. (3) Nerve cells in layers IV‐VI of the lateral striate cortex (binocular Vl) send a restricted projection to the lateral portion of the occipital cortex. (4) After all lesions of the striate and/ or occipital cortices, degenerating fibers are seen radiating away from the lesion in layer I; the origin of these degenerating fibers could not be determined.The following observations have been made concerning the origins and terminations of commissural corticorticalfihers. (1) After ablation of most of the visual cortex of one side, commissural fibcrs are secn to terminate in all cortical layers in two narrow bands of visual cortex: one band occupies both sides of the striate‐occipital boundary; the second band is found in the lateral portion of occipital cortex. (2) More punctate lesions reveal that commissural fibers arise from layers IV‐VI of the lateral striate cortex and medial occipital cortex (binocular portions of V1 and V2 respectively) and end in hornotopic areas of the contralateral cortex.
The organization of thalamocortical relay neurons in the rat ventrobasal complex studied by the retrograde transport of horseradish peroxidase
Authors: Saporta Samuel , Kruger Lawrence 
Published: December 2004

AbstractThe organization of thalamocortical relay neurons in the thalamic ventrobasal complex (VB) of the rat was investigated by the use of the retrograde axonal transport of horseradish peroxidase (HRP). Injections of HRP into somatosensory cortex (SI) resulted in a distinctive gradient of neuronal and non‐neuronal HRP reaction product. Electrophysiologically characterized points of SI injected with small volumes of HRP labeled a sector of neurons in VB ipsilateral to the injection. This zone of labeled neurons consisted of a complex curvilinear array or lamina with a rostral hollow or solid expansion of densely packed HRP positive neurons which continues caudally as a less dense tapering wing. Despite this complex arrangement, an approximate pattern of somatotopy was determined indicating the direction of shifts in peripheral receptive fields moving in any axis of VB. The number of labeled neurons projecting upon a point in SI was also determined. Injections of the cortical vibrissae, face and forepaw representations labeled a greater number of neurons in VB per unit area of cortex than did injections in the hindlimb or body representations. The total number of HRP positive neurons in VB increased proportionately with areal increase of the HRP injections into overlapping cortical representations. The number of HRP positive neurons in the rostral half of the laminae increased almost linearly with the area of injection, while the number of HRP positive neurons in the caudal half of the laminae showed relatively smaller increases.
The ultrastructure of a cerebellar analogue in octopus
Authors: Woodhams P. L. 
Published: December 2004

AbstractThe peduncle lobe of Octopus, a centre concerned with regulating motor behaviour primarily on the basis of visual cues, though it also receives a “labyrinthine” or statocyst input, has been examined for the first time in the electron microsope. In the lower part of the lobe, the basal zone, there are large “motor” cells up to 20 μm across with a rounded, pale nucleus and a large perikaryon; there are also smaller cells, 4‐10 μm in diameter with a dark irregularly‐shaped nucleus. The latter receive synapses from afferent fibres to the lobe, and those from the principal afferent source, the ipsilateral optic lobe, have been characterised as large terminals with many small clear vesicles. Other optico‐peduncular afferents and the small‐cell fibres themselves run directly up to the second part of the lobe, the peduncle spine, which contains exclusively small granular cells about 5 μm in diameter. The fibres of these spine cells form a conspicuous and characteristic array of parallel fibres in the neuropil and they bear a striking resemblance to those of vertebrate cerebellar granule cells: serial synaptic relays are present along their length. These findings, together with earlier evidence about the effects on motor behaviour of lesions to the lobe, suggest a close functional and morphological analogy to a folium of the vertebrate cerebellum. The hypothesis is discussed that parallel fibres, with their narrow diameter and hence long conduction time, are an essential feature of fine motor control systems, and that their primary function is one of providing critical time delays in the millisecond range.
Direct and indirect preoculomotor pathways of the brainstem: An autoradiographic study of the pontine reticular formation in the cat
Authors: Graybiel Ann M. 
Published: December 2004

AbstractThe efferent connections of the paramedian pontine reticular formation have been studied in the cat in autoradiographic experiments designed to analyze direct and indirect preoculomotor pathways. Injections of tritium‐labelled amino acids were placed (1) near the border between the oral and caudal subdivisions of the nucleus pontis centralis, (2) in more rostral and dorsal parts of the pontine tegmentum, (3) at the pontomesencephalic border, and (4) at the pontomedullary border.Tegmental injections of the first group were unique in labelling a direct ipsilateral pathway to the abducens nucleus and nucleus prepositus hypoglossi. More rostral injections failed to produce discrete labelling of the nuclei of the extraocular muscles but labelled nearby tegmentum and central gray substance. Caudal deposits, involving the pontomedullary reticular formation at its junction with the abducens, perihypoglossal and vestibular nuclei, labelled a decussating fiber system reaching the contralateral abducens nucleus, nucleus prepositus hypoglossi and parts of the vestibular complex. In a single additional case, an injection placed in the oculomotor complex produced heavy labelling of the abducens nuclei.All tegmental injections labelled discrete reticulo‐reticular and other variably complex longitudinal pathways. Most injections of (a) the pontomedullary and (b) the pontomesencephalic zones elicited labelling of the pretectum including the nucleus of the optic tract. An incidental finding in the latter group was dense labelling of the pars compacta of the substantia nigra, subthalamic nucleus, and (1 case) entopeduncular nucleus; in one case of each of these groups, labelled fibers were traced to the external pallidum.These observations suggest that, with respect to its efferent oculomotor affiliations, the paramedian pontine tegmentum may be divided into compartments whose supranuclear connections are distinct but for the most part heavily weighted toward influencing the abducens nucleus and periabducens region. Considered within the framework of behavioral and physiological studies of the so‐called pontine gaze center, and studies of pontine afferents, the findings are interpreted as suggesting a functional differentiation of these tegmental zones with respect to their influence on eye‐head coordination.
A comparison of the early development of axodendritic and axosomatic synapses upon embryonic mouse spinal motor neurons
Authors: Vaughn James E. , Sims Terry , Nakashima Mariko 
Published: December 2004

AbstractThe early embryonic development of axodendritic and axosomatic synapses upon motor neurons has been investigated in mouse spinal cord. This investigation had two main objectives: (a) to determine the earliest embryonic day on which recognizable synaptic contacts occur upon motor neurons, and (b) to compare the development of synaptic contacts upon the dendrites and somata of motor neurons during the early synaptogenic period. The broad goal of this investigation was to determine whether the location of early‐forming synapses upon motor neurons is consistent with the possibility that axosomatic synapses might be involved in the primary induction of motor neuronal dendrogenesis.Embryonic day 11 (E11) was the earliest developmental time at which synaptic contacts were observed in developing mouse spinal cord. All of these synaptic contacts appeared to be located upon motor neuronal dendrites within the lateral and ventral marginal zones. The number of synaptic contacts observed on E11 was too small to be detected by the quantitative sampling procedure used in this investigation, but the procedure was sufficiently sensitive to detect synaptic contacts on embryonic day 12. Both axodendritic and axosomatic synapses were found upon E12 motor neurons, but there were about four times as many synaptic contacts per unit length of dendritic membrane as there were per equivalent length of somal membrane. Furthermore, dendritic membranes continued to exhibit a higher density of synaptic contacts on all of the remaining embryonic days (i.e., 13–16) examined in this investigation. These quantitative data and the E11 observations indicate that axosomatic synaptic contacts are not a necessary prelude to the formation of motor neuronal dendrites. Therefore, it is suggested that axosomatic synapses do not play an obligatory role in the primary induction of motor neuronal dendrogenesis.The experimental findings of other investigators, however, have provided reasons to suspect that early‐forming axosomatic synapses may somehow facilitate dendritic development once it has been induced. This possibility is discussed in terms of our observation that early‐forming axosomatic synapses rather commonly occur at sites which may represent somal growth regions. This relationship leads us to suggest that early axosomatic synapses may facilitate dendritic development by signalling the motor somata that the formation of a synaptogenic axonal field is underway. Furthermore, we speculate that the positioning of early axosomatic contacts might be providing directive cues as to the location of the developing synaptogenic field. Thus a directive facilitation of dendritic growth is suggested as a function of early axosomatic synapses rather than one involved with the primary induction of dendrogenesis.
Time dependence of terminal degeneration in spino‐cerebellar mossy fiber rosettes in the chicken and the application of terminal degeneration in successive degeneration experiments
Authors: Vielvoye G. J. , Voogd J. 
Published: December 2004

AbstractMossy fiber rosettes in the granular layer of the cerebellar cortex were studied after sections of the lateral funculus of the spinal cord of the chicken and silver impregnation with the Fink‐Heimer ('67) method I. After a survival time of two or three days two types of degenerated rosettes were found. The first type is characterized by digitiform protrusions, the second type of rosette is spherical. Both types are covered by small argyrophilic particles which disappear when the degeneration proceeds. With longer survival times the rosettes become swollen and finally desintergrate and loss their argyrophilia. After a survival time of 30 days only debris of rosettes can be found.These observations were used to determine the cerebellar cortical projection of mossy fibers originating from segments of the spinal cord isolated in “successive degeneration” experiments consisting of a chronic cordotomy followed by an acute cordotomy rostral to the first one.
Extraocular muscle representation in the brainstem of the carp
Authors: Luiten P. G. M. , Dijkstra‐de Vlieger H. P. 
Published: December 2004

AbstractThe representation of the extraocular muscles in the oculomotor nuclei in the brainstem of the carp was studied with the horseradish peroxidase technique. Some normal anatomical features of the various oculomotor nuclei are described. Following intramuscular HRP injections in the eye muscles and applying survival times of up to 25 days labeled perikarya were found in the various nuclei of the oculomotor complex. Rectus inferior, rectus internus, and obliquus inferior are represented in the ipsilateral nucleus oculomotorius, while the rectus superior was found to be innervated from the contralateral n III. The efferent cells innervating the obliquus superior are located mainly in the contralateral nucleus trochlearis and for a low percentage in the ipsilateral counterpart of the n IV. The rectus externus is represented in the rostral and caudal subnuclei of the ipsilateral nucleus abducens. These results show a remarkable resemblance with data on mammalian extraocular muscle representation, although the overlap of the various cell populations is larger in fish.