摘要:

AbstractFolowing unilateral HRP injections in the optic tectum ofRan pipiens, HRP ‐ positive cells were seen in three pretectal nuclei: bilaterally in the dorsal posterior nucleus; in the dorsal half of the ipsilateral posterior nucleus; and ipsilaterally in the large‐celled pretectal nucleus. HRP ‐positive cells were also seen ipsilaterally in the anterodorsal, posterodorsal and posteroventral tegmental fields, the nucleus isthmi, and the dorsal gray columns of the cervical spinal cord; bilaterally in the suprapeduncular nucleus, a paramedian cell group dorsal to the interpeduncular nucleus; and in the deep layers of the contralateral tectum. In addition, evidence for a bilateral ventral preopto‐tectal projection was seen in half the experimental animals. No tectal afferents from telencephalic or rostral thalamic areas were seen. Both the ascending and descending tectal efferent fibers were also filled with reaction product. The pale reaction indicative of terminating tectal efferents was seen in the dorsal pretectum, partially overlapping the lateral nucleus and uncinate neuropil; in the core of nucleus isthmi; and in the superio

ISSN:0092-7317    

DOI:10.1002/cne.901730202

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe development of the entorhinal, ipsilateral associational, and commissural afferents to the dentate gyrus have been studied autoradiographically, following the injection of small amounts of tritiated proline into the medial and lateral parts of the entorhinal cortex, and into fields CA3cand CA4of the hippocampus, ia series of rats, on the third, sixth, and twelfth postnatal days. Clear labeling of the entorhinal afferents was found at the third postnatal day, and from the earliest stage studied the afferents from the two parts of the entorhinal cortex appear to be spatially segregated within thestratum moleculareof the dentate gyrus: the fibers from the lateral entorhinal areà occupying the outermost one‐third, or so, of this stratum, while those from the medial entorhinal cortex occupy its middle zone. The ipsilateral hippocampo‐dentate associational pathway is present at the third postnatal day, but the commissural projection (which shares wiht it the inner part of the stratum moleculare) could not be labeled until the sixth postnatal day. By the twelfth day the characteristic adult pattern of distribution of the terminals of the two hippocampo‐dentate pathways is established. although this pattern is best accounted for on the basis of a temporal competition for the available synaptic sites on the proximal parts of the dendrites of the granule cells, the spatial segregation of these two fiber systems from those arising in the entorhinal cortex, is probably due to the selective fasciculation of fibers in each group of afferents and to their early cytochemical speci

ISSN:0092-7317    

DOI:10.1002/cne.901730203

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractVisual information reaches the dorsal thalamus by two distinct routes in most reptiles. Retinal efferents terminate directly in the dorsal lateral geniculate nucleus (DLGN). Retinal information is also channeled indirectly through the tectum to nucleus rotundus. Retinal projections to DLGN and tectum are also well esablished in snakes, but the status of the tecto‐rotundal link of the indirect visual pathway is uncertain.Thus, tectal efferents were studied with Fink‐Heimer methods in banded water snakes (Natrix sipedon). The tectum gives rise to crossed and uncrossed projections to the brainstem reticular formation. Commissural connections are effected with the contralateral tectum via the tectal and osterior commissures. tectum projects densely to the ipsilateral basal optic nucleus. Bilateral ascending projections reach the pretectal area, nucleus lentiformis mesencephali, lateral habenular nuclei, and posterodorsal nuclei. Ascending projections reach the ventral lateral geniculate and suprapeduncular nuclei. there is a diffuse projection to the central part of the caudal thalamus and a dense, bilaternal projection to the DLGN.These results indicate that the relation of the tectum to the dorsal thalamus is different in snakes than in other reptiles. Nucleus rotundus is either absent or poorly differentiated and there is a strong convergence of the direct and indirect visual pathways at D

ISSN:0092-7317    

DOI:10.1002/cne.901730204

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe retina of the normal pigmented mink has been studied by light and electron microscopy. This retina resembles the typical vertebrate retina in its pastterns of lamination and synaptic interconnectivity. Rod and cone outer segments and receptor spherule and pedicle endings are found. At least two different types of horizontal cell processes are seen with the electron microscope, suggestive of rabbit A and B types. Ribbon and conventional synapses are found in both plexiform layers; conventional synapes are also present in the inner nuclear layer. Quantitative studies of the inner plexiform layer revealed amacrine:bipolar synapse ratios (3.3:1) similar to those of the cat and monkey. Other quantitative parameters also resembled those previously reported for species with retinas that predominantly contain concentric‐type receptive field

ISSN:0092-7317    

DOI:10.1002/cne.901730205

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractMost cells of the dorsal lateral geniculate nucleus of rats are generated of fetal days 12 to 14. Their axons invade the telencephalon on fetal day 16 and run in the intermediate zone just below the cortical plate, reaching the visual area on fetal day 18. The axons do not invade the cortical plate significantly until close to birth (day 22 of gestation) and reach their zone of terminal distribution between postnatal days 1 and 4. In subsequent days the projection becomes progressively more heavily distributed in layers IV and I, and synapses of thalamic origin can be identified in these layers. While cells destined for layers IV cross the intermediaste zone at the time that thalamic axons first arrive, this coincidence of growth does not seem to be a factor which determines the specificity of patterns of thalamocortical connections since the cells reach layer IV several days before the axons. It is unclear why the axons should wait several days in the region immediately below the cortical plate before invading, although there is a parallel in previous studies on the development of the chick retinotectal pathway (Crossland et al., '75).

ISSN:0092-7317    

DOI:10.1002/cne.901730206

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe winter flounder shifts the orientation of its body 900at 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.

ISSN:0092-7317    

DOI:10.1002/cne.901730207

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe distribution of monoamine‐containing neurons in the CNS of the developing and adult axolotl,Ambystoma mexicanum, has been investigated using the histochemical fluorescence technique of Falck and Hillarp combined with microspectrofluorimetry. The earliest catecholamine‐containing neurons to be detected are located in the ventral ependymal zone of the spinal cord at the time of hatching (Stage 41). Between stages 43 and 46, catecholamine fluorescence can be detected in neurons in the following regions: nucleus preopticus, the hypothalamic‐infundibular region, and the brain stem reticular fomation. 5‐HT‐containing neurons are only observed in the midbrain raphe region and are first detected at stage 44. In contrast to these early monoamine fluorescing groups, catecholamine‐containing neurons are not routinely detectable in the nucleus interpeduncularis until six months of age. All monoamine‐containing neuronal groups detected in developing axolotls are also present in both sexes of the adult. However, the fluorescence intensity is less in monoamine‐containing neurons observed in adults than in early developing subjects.All catecholamine‐containing neuronal groups, with the exception of those located in the midbrain region (nucleus interpeduncularis, reticular zone) have fluorescent processes that contact the cerebrospinal fluid (CSF). The presence of CSF‐containing processes in the hypothalamic and spinal cord regions suggest that the CSF may act as a medium through which bioactive substances are transported from one brain region to another. Intense catecholamine fluorescence is observed in cells of the notochord prior to the detection of monoamine‐containing neurons in the CNS. A possible involvement of catecholamines in the inductive effects of the notochord during dev

ISSN:0092-7317    

DOI:10.1002/cne.901730208

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

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.

ISSN:0092-7317    

DOI:10.1002/cne.901730209

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe posterior neocortex in the gray squirrel,Sciurus carolinensis, includes an extensive region which receives projections from the pulvinar. Previous studies have demonstrated that this cortical region can be subdivided on the basis of differences in cytoarchitecture and electrophysiologically defined representations of the visual field. The main purpose of the present paper was to determine whether these cortical subdivisions could be related to corresponding subdivisions in the pulvinar. The methods used to trace connections included anterograde degeneration, anterograde axonal transport of tritiated amino acids and the retrograde axonal transport of horseradish peroxidase. The results indicate that the pulvinar in this species contains at least three main subdivisions which can be distinguished by their cytoarchitecture and their patterns of connections. A caudal subdivision contains large, evenly‐spaced neurons and receives bilateral input from the superficial, retinal‐recipient layers of the superior colliculus. This caudal subdivision has reciprocal interconnections with a cytorchitectonically ditinct area in the temporal cortex. A rostro‐lateral subdivision contains smaller, more lightly stained neurons which tend to form cluster. This subdivision receives only ipsilateral tectal input and projects to occipital area 18. This subdivision does not receive input form areas 17, 18, and 19, or form the temporal cortex. Finally, a rostro‐medial subdivision is cytoarchitectonically similar to the rostro‐lateral subdivision but receives little, if any, input form the superior colliculus. This rostro‐medial area does, however, receive corticofugal projections form occipital areas 17, 18, and 19, and projects to area 19. These patterns of connections suggest that each of these subdivisions has close associations with the visual system. The question of whether similar subdivisions are present in the visual thalamus of other species i

ISSN:0092-7317    

DOI:10.1002/cne.901730210

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

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 se

ISSN:0092-7317    

DOI:10.1002/cne.901730211

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY