摘要:

AbstractEfferent neurons innervating the vestibular labyrinth and cochlea of the pigeon have been identified by means of a variety of retrograde tracers: [3H]‐adenosine (Ad), horseradish peroxidase (HRP), Evan's Blue (EB) and Bisbenzimide (Bb). Discrete injections into individual cristae ampullares of the semicircular canals, into the macula utriculi, or into several of these end organs resulted in similar patterns of neuronal labelling. Efferent vestibular neurons were always found within a small portion of the nucleus reticularis pontis caudalis (RP), ventrolateral to the abducens nucleus on both sides. No systemic difference in the locations of labelled cells was found following injection into different sensory epithelia. Cell counts following injections into individual cristae did not differ significantly from those following injections into all three cristae. The injections into all cristae in both labyrinths yielded cell counts that were much lower than twice the number of cells labelled by injections into the three cristae on one side only. When HRP was injected into the right lateral canal crista and Ad into the right posterior canal crista, a high proportion of neurons was labelled with both compounds (61% of the HRP‐labelled cells and 67% of the Ad‐labelled cells). Injection of EB into all three cristae on the right side and Bb into all three cristae on the left side produced a smaller percentage of doubly labelled cells (10% of the EB‐labelled cells and 6% of the Bb‐labelled cells). It is concluded, therefore, that there is a considerable degree of collateralization within one labyrinth. Fewer collaterals of efferent neurons are directed to both labyrinths. Since each semicircular canal represents head rotation in one direction and one plane, it is unlikely that efferents which contact several different movement sensors can provide sensory motor control that is specific for directions and planes of head movements.Control injections of these tracers into the cochlea yielded labelled cells in a different reticular structure, the nucleus reticularis paragigantocellularis lateralis (Pgc), on both sides, as well as in the RP. It is proposed that the Pgc cells represent cochlear efferents, while the RP neurons are related to the macula lagenae, an otolithic organ of balance in t

ISSN:0092-7317    

DOI:10.1002/cne.901960102

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe largest receptive fields mapped during microelectrode penetrations through the upper strata of the cat's superior colliculus vary substantially in size and shape in different collicular regions. Previous work has shown that when these large fields are plotted in the retinotopic map of the colliculus, their profiles become elliptical and vary little in size and orientation over the central regions of the map. Such profiles are called thereceptive field images(RFIs) in the visual coordinate system of the colliculus. Of particular interest here is the relationship of these RFIs to the region of the colliculus occupied by cells whose receptive fields include a common visual point. We call this region thepoint imagein the colliculus. A straightforward geometric argument indicates that the point image in the upper collicular strata should have the same size, shape, and orientation as the RFIs of the large‐field cells recorded here, if, indeed, these RFIs are translationally invariant as suggested by the earlier studies.The experiments reported here directly assessed the translational invariance of large‐field RFIs in the superior colliculi of individual cats. The results support the previous inference that the profiles are oval with their long axes oriented mediolaterally. The mediolateral and anteroposterior dimensions of the profiles were about 2.7 and 2.0 mm, respectively, wherever they were measured in the central regions of the colliculus. Since the boundaries of the point images in the superficial strata must have similar shape and dimensions, these data indicate that a visual point is “seen” by collicular cells spread through a substantial fraction of the tissue recieving the projection of the contralateral visua

ISSN:0092-7317    

DOI:10.1002/cne.901960103

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractParallel single unit and retrograde tracing experiments were carried out in the anesthetized cat to elucidate the representation of the auditory and somatosensory systems in the external nucleus of the inferior colliculus (ICX).Units responding to tonal stimuli were more commonly encountered in ICX and the adjacent intercollicular area (ICA) than were units with identified tactile receptive fields. Concomitantly, a larger number of retrogradely labeled cells were identified in midbrain auditory structures, following injections of horseradish peroxidase (HRP) into ICX, than were found in the combined dorsal column nuclei.Microelectrode recording revealed that the entire accessible body surface was represented in ICX, and receptive fields of individual units were usually large and mostly located on the contralateral side. HRP‐labeled cells were scattered throughout the contralateral cuneate, gracile, and spinal trigeminal nuclei. tations of tone pips. Responses to complex sound were commonly observed. Binaural stimuli influenced the firing of the majority of auditory units. Labeled auditory neurons following ICX injections were found mainly in the inferior colliculus of both sides. Spread of tracer into the central and pericentral nuclei was associated with labeling of many neurons in hind brain auditory structures.Only vague suggestions of somatotopy or tonotopy were observed in the electrophysiological experiments; similarly, no topographical relationship between HRP injection site and locus of retrograde label in a given projecting nucleus could be discerned.Speculations were made, in the light of the dual convergent sensory representation in ICX, about the role of this structure in acoustico‐motor mechani

ISSN:0092-7317    

DOI:10.1002/cne.901960104

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractWe have investigated the morphology of the giant interneurons (GIs) and the main sensory projections to these interneurons in the American cockroach. These neurons are thought to mediate the animal's escape behavior. We describe here the dendritic branching pattern of each of the 14 GIs (7 bilateral pairs) in the terminal ganglion, the pattern of projection of the cercal sensory nerve, and the overlap of the cercal projections with the dendrites of the GIs. Visualization of the GIs and cercal nerve projection was accomplished by single cell injection and axonal backfilling with cobalt. Comparisons of the same identified GI in different animals show the position of the soma and the locations and orientations of the major processes are characteristic for each GI. The axons of the cercal nerve project to a well‐defined ipsilateral region of the terminal ganglion. After entering the terminal ganglion, the cercal afferents split into lateral and medial tracts. The projections of the lateral cercal tract overlap extensively with the dendritic fields of the GIs. In contrast, the medial tract does not overlap the dendritic fields of the GIs in the posterior portion of the ganglion and shows only a small degree of overlap in the anterior portion. Correlations between physiological properties of the GIs and cercal afferents are discussed in relation to our anatomical finding

ISSN:0092-7317    

DOI:10.1002/cne.901960105

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractFollowing axotomy, motoneurons of the opossum spinal cord display an early “axon reaction” or “chromatolysis” characterized by a redistribution of ribosomes accounting for a widespread basophilia and an apparent reduction in the size of two distinct varieties of Nissl bodies. This alteration is accompanied by zones of increased extracellular glycocalyx demonstrable in light and electron microscopy. In addition, large intracellular periodic acid‐Schiff‐positive vacuolated zones in the neuron periphery possess numerous free ribosomes, glycogen, lipids, and huge vacuolated sacs containing a flocculent matrix material similar to that found within the sacs of granular endoplasmic reticulum. “Artifacts” in the neuronal periphery associated with chromatolysis seen in light microscopy are probably related to polysaccharide alterations and redistribution of granular endopl

ISSN:0092-7317    

DOI:10.1002/cne.901960106

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase (HRP) was used to determine the location in the spinal cord of neurons projecting to the superior cervical ganglion of the rat. HRP was applied to the proximal cut end of the cervical sympathetic trunk, close to its entry into the superior cervical ganglion. After survival times of 3, 6, or 9 days, the animals were sacrificed and their spinal cords were processed to visualize HRP using diaminobenzidine, benzidine dihydrochloride, or tetramethylbenzidine. Labeled neurons were found only ipsilateral to the site of HRP application and were restricted to spinal segments C8‐T5. Ninety percent of these neurons were located in segments T1‐T3. Similar numbers of labeled neurons were found at survival times of 3 and 6 days and the mean number ± S.E.M. for 11 experiments at these two survival times was 1575 ± 89. Nine days after application of HRP the mean number of labeled cells and the density of label per cell were reduced. Labeled neurons were found in four regions of the spinal cord: the intermediolateral nucleus (75%), the lateral funiculus (23%), the central autonomic area (1%), and the intercalated region (1%). The cells of the intermediolateral nucleus did not form a continuous column along the rostrocaudal axis of the spinal cord, but instead were often found in clusters, several clusters being present per spinal se

ISSN:0092-7317    

DOI:10.1002/cne.901960107

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractBipolar neurons in the medial superior olivary (MSO) nucleus of albino rats were studied at various ages (0–75 days) during development in order to elucidate normal neuronal growth patterns. Neurons, visualized in celloidin embedded Golgi/Nissl‐ and frozen Nissl‐stained sections, were analyzed quantitatively for cell size and extent of dendritic arborization. These parameters, from both sets of data, showed a consistent developmental trend with the existence of two major stages in the ontogenetic process: a rapid developmental and a stabilization stage. The first stage, encompassing postnatal days 0 through approximately 14, was characterized by a rapidly increasing cell size, as observed in frozen sections. At the peak of this rapid growth, Golgi‐stained neurons possessed thick dendrites with many appendages, growth cones, and filopodia. The peak in neuronal development coincided with the initiation of ear opening. Morphological features attained a more mature form in the second, stabilizing stage of development, which began at approximately postnatal day 14. This phase was distinguished by a decrement in cell size and dendritic branching. Also, dendrites possessed more regularly distributed varicosities and fewer appendages, growth cones, and filopodia in this period. It was observed that dendritic branching trends paralleled those of cell diameter

ISSN:0092-7317    

DOI:10.1002/cne.901960108

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe time of origin of neurons in the hippocampal region was determined in a series of rhesus monkeys, each of which had been exposed to a pulse of tritiated thymidine (3H‐TdR) at a different time during ontogeny and sacrificed between the second and fifth month after birth. No heavily labeled cells were found in the hippocampal region of animals exposed to3H‐TdR before embryonic day 33 (E33). Exposure to3H‐TdR given at E36 labels a few neurons in the deepest layers of the entorhinal area, and3H‐TdR given at E38 labels a small number of neurons in all hippocampal subdivisions. Although the first neurons are generated almost simultaneously throughout the hippocampal region, the proliferation ceases at a different time in each subdivision. The last neurons destined for the entorhinal area and presubiculum are generated between E70 and E75, whereas the last parasubicular neurons are generated between E75 and E80. The production of neurons that form the subiculum ends about two weeks earlier, between E56 and E65. Within the hippocampus, genesis of pyramidal cells ends between E70 and E80 in area CA1, between E56 and E65 in area CA2, between E65 and E70 in area CA3, and between E75 and E80 in area CA4. In contrast, the genesis of granule cells of the fascia dentata is considerably prolonged. It continues throughout the second half of gestation, declines steadily in the course of the first postnatal month, and tapers off during the next 2 months.There is a distinct inside‐to‐outside spatiotemporal gradient in the parahippocampal formation and in the stratum pyramidale of both the subiculum and hippocampus. In contrast, the spatiotemporal pattern of granule cell origin in the dentate gyrus is outside‐to‐inside. Furthermore, granule cells generated between E36 and E80 are distributed in a distinct suprapyramidal‐to‐infrapyramidal gradient, whereas those generated at later ages are distributed evenly throughout the fascia dentata. Correlation of the present findings with histological data on hippocampal neurogenesis in the human brain demonstrates that the timing and sequence of developmental events as well as spatiotemporal gradients are similar in b

ISSN:0092-7317    

DOI:10.1002/cne.901960109

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe site of origin and route and rate of migration of neurons in the developing hippocampal region of the rhesus monkey were studied with tritiated thymidine (3H‐TdR) autoratiography. Analysis of specimens sacrificed approximately 1 hour after exposure to3H‐TdR shows that the neurons destined for the hippocampus and subiculum are generated exclusively in the ventricular zone lining the medial wall of the lateral cerebral ventricle. In contrast, neurons of the parahippocampal formation are generated in two proliferative zones: The majority of neurons destined for the lamina principalis interna arise from the ventricular zone, whereas most of those destined for the lamina principalis externa originate from the subventricular zone. The neurons of the dentate gyrus are also generated in two locations: in the ventricular zone (between E38 and E85) and within the prospective hilus of the dentate gyrus (from E58 up to approximately 3 months after birth).Analysis of specimens sacrificed at progressively longer intervals after exposure to3H‐TdR indicates that neurons destined for all of the subdivisions of the hippocampal region (except those cells generated in the hilus of the dentate gyrus) migrate through the intermediate zone, bypassing previously generated neurons on their way to the superficial limits of the developing cortical plate. Estimated migration rates are approximately 15 μm/day in the sector of the hippocampal formation, about 100 μm/day in the parahippocampal formation, and about 115 μm/day in the region of adjacent neocortex. Thus simultaneously generated neurons destined for three distinct cytoarchitectonic areas have significantly different rates of cell migration. These differences are unrelated to the length of cell trajectories and may depend on the mechanism of cell translocation and/or the timing of signals that initiate cell movement. The differential rate of migration indicates that the fate of postmitotic cells may be determined before they have reached their final des

ISSN:0092-7317    

DOI:10.1002/cne.901960110

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe central projections of the retinal ganglion cells of the golden hamster were examined using horseradish peroxidase (HRP) as the anterograde tracer molecule. Following monocular injections of HRP into the vitreous, retinfugal fibers were histochemically demonstrated using the chromagen tetramethylbenzidine. This procedure, being more sensitive than the3H‐amino acid radioautographic technique, provided a clear demonstration of previously controversial retinal projections, clearer definition of established projections, and the discovery of new retinal pathways.An inferior accessory optic system was shown to be unequivocally present in this species and to consist of both crossed and uncrossed components. A direct retinal projection to the suprachiasmatic nucleus (SCN) of the hypothalamus was confirmed in this study. But the distribution of terminals as seen by this procedure was substantially different than previously reported; both rostrocaudal and mediolateral asymmetries in the distribution of label between the ipsilateral and contralateral SCN were observed. Substantial differences in the retinal projection to the SCN in the hamster and the rat were also noted. It is suggested that these differences may reflect the different effects photic input has on the neuroendocrine‐gonadal axis in these two species. Finally, labeled retinal axons were followed leaving the optic tract and coursing anteriorly through the plexiform layer of the piriform cortex; other labeled fibers were seen to enter the septal region. The physiological significance of these previously undescribed retinal projections is not kn

ISSN:0092-7317    

DOI:10.1002/cne.901960111

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY