摘要:

AbstractIn the rhesus monkey, the caudal portion of the superior temporal sulcus (STS) receives a direct projection from lateral striate cortex, the striate area representing central vision. The present study was undertaken to determine whether STS also receives a direct projection from areas of striate cortex representing peripheral vision, with the intent of defining the entire striate projection zone in STS as well as providing information regarding a possible topographic organization within this secondary visual area. A series of five rhesus monkeys was prepared with unilateral lesions of lateral, posterior, or medial striate cortex, such that, collectively, the lesions in the series included all of striate cortex with little or no invasion of prestriate cortex. The monkeys were sacrificed seven days after surgery and their brains were processed by the Fink‐Heimer procedure. An analysis of the distribution of terminal degeneration within STS indicated: (1) All areas of striate cortex project to a restricted region along the caudal portion of STS. The ventral limit of this region can be demarcated by an imaginary line connecting the ventral tips of the lunate and intraparietal sulci; from this limit the region extends dorsocaudally for approximately 12 mm to the point at which STS frequently bifurcates, sending one spur forward into the inferior parietal lobule. (2) Within this portion of STS there is an orderly mapping of the visual field; progression from central vision to the far periphery is represented by a progression down the posterior bank of STS and continuing along the entire floor, or insula‐like portion, of the sulcus. (3) Projections from striate cortex to STS terminate predominantly in layer IV and the deep part of layer III. (4) There is a distinctive pattern of myelination contained within the striate projection zone of STS. These anatomical findings concerning the striate projection zone of STS. in the rhesus monkey are remarkably similar to those that have been described for the middle temporal visual area (MT) in New World monkeys, and thus support earlier proposals that the two areas are homolog

ISSN:0092-7317    

DOI:10.1002/cne.901880302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe fine structure of the abdominal ganglion of Aplysia californica has been studied in preparations fixed by immersion in aldehydes, either directly or after a survival of a few hours in artificial sea water. The central core of neuropil is surrounded by a rind of neuronal cell bodies floating in a subcapsular space containing a loose mesh work of neuronal and glial processes, separated by wide extracellular spaces. Large primary processes with deeply infolded membranes leave the neuronal perikarya and enter the neuropil where they branch into smaller processes containing either neurofilaments, neurotubules or both. Some have the appearance of initial segments. The neuropil is not a homogenous structure. Rather, four types of zones can be distinguished: (1) zones of fibers of passage coursing together in the neuropil and making few synaptic contacts; (2) zones of neurosecretory fibers containing large granules and dense‐core vesicles, again making few synaptic contacts; (3) zones with a great variety of synaptic contacts between medium size and small profiles; and (4) glomerular zones. The differentiated membranes of the synapses are characterized by a slight increase in density and by being regularly parallel to each other. Presynaptic densities are sometimes quite prominent but specialized dense cytoplasmic opacities have never been seen bordering the postsynaptic membranes, i.e., all synapses are of the symmetrical type. Interlemmal opacities vary considerably in density. In zone 3, the synaptic vesicles are of several sizes, are round, oval or flat, and are either clear or filled with different types of dense material. The population of vesicles within a single profile may consist either of a homogeneous group of similar vesicles, or of various mixtures of two or three kinds of vesicles. In profiles with mixtures of clear and large dense‐core vesicles, it is often only the clear vesicles which agglomerate towards the differentiated membranes. In such cases the large dense‐core vesicles lie as a peripheral halo around the clear vesicles. Here, and especially in other large neuronal profiles not forming contact in the plane of section, they can be seen to associate specifically with mitochondria and glycogen. It is proposed that they do not contain neurotransmitters but are related to mitochondrial activities such as the strorage of ATP or the movement of calcium ions. In profiles with mixtures of clear and small dense‐core vesicles, both types of vesicles often touch the presynaptic membrane, suggesting the release of two transmitters or of a modulator or neurohormone with a transmitter, by a single terminal. Serial synapses are present in this zone. The glomerular zones contain small profiles forming many synaptic contacts, some of which are arranged in such a way as to suggest the existence of “reciprocal” seri

ISSN:0092-7317    

DOI:10.1002/cne.901880303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractTwo types of glial cells have been identified in the neuropil and in the subcapsular space of the abdominal ganglion of Aplysia californica. In the neuropil, a first type of glial cell has a light staining cytoplasm and gives rise to processes which may contain bundles of filaments, a flocculent material or bundles of microtubules and membranous sacs. Synaptic contacts have been seen very rarely on their somata and more frequently on their “filamentous” and “flocculent” processes. A second type of glial cell has a darkly staining cytoplasm and gives rise to dense processes. Synaptic contacts are frequently seen on these processes. In the subcapsular zone, there are also two types of glial cells, one with a clear and the other with a dense cytoplasm. The processes of the clear glial cells contain glycogen‐like particles and sometimes bundles of filaments. These processes surround the bundles of neuronal profiles which form the perisomatic plexus. Such enveloping processes receive synaptic contacts from the neuronal profiles in the bundles. The dense glial cells of the subcapsular zone also receive synaptic contacts, but this is a rare o

ISSN:0092-7317    

DOI:10.1002/cne.901880304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractReceptive field characteristics of single cells in primary visual cortex of rabbit were studied. Seventy‐two percent of cells were found to be orientation selective, and the remainder had concentric, uniform, movement selective or pure direction selective receptive fields. Single cells were also recorded from primary visual cortex of cat to permit a comparison of visual cortical organization in cats and rabbits. Laminar organization of receptive field types was observed in rabbits which was similar in most respects to that described in the cat. Although the major categories of orientation selective cells (simple, complex, hypercomplex) were similar for both cat and rabbit, many differences emerged: (I) tuning of orientation selectivity was narrower in cats than in rabbits; (II) units which preferred oblique orientations were less frequently represented in rabbits than in cats; (III) orientation preferences appeared to be arranged in cluster in rabbit cortex; in rabbits we found no evidence of the columnar organization of orientation selectivity which characterizes cat visual cortex.A comparison of our data with those previously reported for mouse, rat, hamster and opossum visual cortex suggest that mammals in which a significant proportion of visual cortical cells are not orientation selective have in common certain patterns of cortical organization involving a less precise and less specialized representation of stimulus orientatio

ISSN:0092-7317    

DOI:10.1002/cne.901880305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractSpiral ganglion cells in the cochleas of Sprague‐Dawley rats in various age groups were counted in order to assess the extent and location of cell degeneration with age. Cells in every tenth section of serially sectioned plastic embedded cochleas were counted in the light microscope. The median cell number for the 1‐ to 2‐month‐old animals was 15,800 cells. This number was first seen to be significantly reduced ( −14%) in the 23‐ month‐old animals. At 27 to 29 months the ganglion cell number was reduced' by 20%, while at 33 to 34 months there was a 17% loss. Losses were found throughout the length of the ganglion with the greatest losses at the lower basal and apical ends. In the oldest group, these losses amounted to 28% and 33%, respectively.Type II ganglion cells first showed a significant decrease in number in the 27 ‐ to 29‐month‐old group, when a 32% loss was seen. The same loss was seen in the 33‐ to 34‐month‐old group. Unlike the type I cells which are lost throughout the length of the ganglion, type II cells were not significantly reduced in number at the basal end, but decreased by as much as 42% in the

ISSN:0092-7317    

DOI:10.1002/cne.901880306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe cells of origin of the long descending propriospinal tract (LDPT) in the cervical enlargement were studied in cat and monkey by using the retrograde transport of horseradish peroxidase (HRP). Their distribution was confirmed electrophysiologically in cat by recording their antidromic action potentials.In cats and monkeys unilateral injections of HRP were made into the gray matter of the lumbosacral enlargement, but there was some spread to the contralateral side. In cats labeled somas were found in greatest numbers in lamina VIII and medial lamina VII, bilaterally. Labeled cells also were found bilaterally in laminae I, IV–VI, and X, but few were in IV and VI. Those in lamina V were usually in the lateral part of the lamina near the reticulated region. The cross‐sectional areas of 20 neurons from each of laminae I and V–VIII were measured. Cells in lamina I were smallest and the largest were in VII and VIII.In cats with the spinal cord hemisected between the injection site and the cervical enlargement containing the somas, the bilaterality of the LDPT neurons in laminae VII and VIII was confirmed anatomically and physiologically. Contralaterally projecting neurons in laminae VIII and medial VII constituted a majority of LDPT cells in those laminae. The LDPT neurons in the dorsal horn appeared to project mainly ipsilaterally, but the number of labeled dorsal horn cells in these preparations was small.The distribution of antidromically localized cells of the LDPT was found to be in good agreement with the anatomical results. Their conduction velocity was 59 ± 22 m/s (mean ± s. d., n = 245). Histograms of the conduction velocity by laminae are given.In monkey the distribution of labeled somas was similar to that in the cat, except that the concentration of labeled somas in the ventral horn was more medially and dorsally located. Labeled somas were found bilaterally in laminae I, IV – VIII, and X, but more appeared to be ipsilateral to the side of the injection, especially in the dorsal horn. The bilaterality of the LDPT in the monkey was not tested with hemisections of the spinal cord.Neurons of the LDPT are ideally situated for conveying sensory information from the forelimb for eliciting reflexes in the hindlimb, as has been observed after stimulating afferents in the forelimb, and for coordinating, in general, motor functions between the two pairs

ISSN:0092-7317    

DOI:10.1002/cne.901880307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractGroups of pregnant rats were injected with two successive daily doses of3H‐thymidine from gestational days 13 and 14 (E13 + 14) until the day before birth (E21 + 22). With this progressively delayed comprehensive labelling procedure we determined the time of origin of neurons in the nuclei of the epithalamus, thalamus, and ventral thalamus. The zona incerta, subthalamic nucleus, are composed of the earliest arising neurons (E13, or before, to E15). The neurons of the lateral habenular nucleus are produced between days E13–16. The neurons of the medial geniculate and lateral geniculate nuclei, the ventrobasal and ventrolateral complexes, and the nucleus lateralis, pars posterior, arise rapidly on days E14–15; the medial geniculate nucleus with a peak on day E14, the others with a peak on day E15. Neurons of a group of nuclei, with ill‐defined boundaries medial to the sensory relay nuclei, arise apparently on days E15–16, with a peak on day E15; these may represent the intralaminar nuclei. The next group is generated on days E15–16 but with peak formation time on day E16: this includes the anteroventral, anterodorsal, anteromedial and mediodorsal nuclei. The rhomboid, reuniens and paratenial nuclei, and the paraventricular nucleus, pars anterior, arise next (E16–17). The medial habenular nucleus forms last and over a protracted period (E15–19). With their lengthy generation time the lateral and medial habenular nuclei resemble more the nuclei of the hypothalamus than the nuclei of the

ISSN:0092-7317    

DOI:10.1002/cne.901880308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractGroups of pregnant rats were injected with two successive daily doses of3H‐thymidine from gestational days 13 and 14 (E13 + 14) until the day before birth (E21 + 22). Internuclear and intranuclear cytogenetic gradients were examined in radiograms of the thalamus sectioned in the coronal, sagittal and horizontal planes. There was a precise and segregated lateral‐to medial gradient between and within the habenular nuclei. In the ventral thalamus the reticular nucleus had a lateral‐to‐medial gradient, the subthalamic nucleus a laterodorsal‐to‐medioventral gradient. There was a caudal‐to‐rostral gradient between the medial geniculate and dorsal lateral geniculate nuclei, and between the pars posterior and pars anterior of the lateral nucleus. A clear intranuclear gradient could not be detected in the sensory relay nuclei with the exception of the medial geniculate nucleus. A lateral‐to‐medial internuclear gradient was seen between the relay nuclei and the intralaminar nuclei, and between the latter and some of the midline nuclei.On the basis of a consideration of the time of origin and time span of production of neurons of various thalamic nuclei, and taking into account some of the recognizable internuclear and intranuclear gradients, the thalamus was divided into five principal cytogenetic components: the epithalamus, the ventral thalamus, the dorsal thalamus, the medial thalamus, and the posterior thalamus. The epithalamic nuclei form over a protracted period resembling the nuclei of the hypothalamus. The nuclei of the ventral thalamus are generated early and over a relatively long period. The dorsal thalamus consists of the relay nuclei and the intralaminar nuclei; they form rapidly and ahead of the medial thalamus. The medial thalamus was subdivided into the earlier‐forming antero‐medial nuclei and the latest‐forming midline nuclei. The posterior thalamus w

ISSN:0092-7317    

DOI:10.1002/cne.901880309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe development of the thalamus was examined in normal and X‐irradiated embryos from day 13 (E13) to the day before birth (E22). The differentiating, radioresistant neurons of the lateral habenular nucleus, derived from a portion of the superior neuroepithelial lobule (SL1), were settling by day E15 and by this time the habenulopeduncular tract was forming. The neurons of the reticular nucleus, derived from the middle neuroepithelial lobe, began to settle on day E15 but a massive migration was still evident on day E16. Adjacent to the reticular nucleus the internal capsule appeared on day E16; this fiber bundle seemed to be continuous with fibers embedded in the first transitory zone of cells issuing from the dorsal neuroepithelial lobe. Because of the immaturity of the neocortex at this time, it was postulated that thalamocortical fibers of the dorsal thalamus are the earliest components of the internal capsule. By day E17 all the sensory relay nuclei of the thalamus were recognizable and it was assumed that the second transitory zone issuing from the receding dorsal neuroepithelial lobe contained the neurons of the later forming intralaminar nuclei. Suggestive evidence was obtained that the late arising neurons of the medial thalamus (the anterior nuclei, the mediodorsal nucleus, and some or all of the midline nuclei) originate in a portion of the superior neuroepithelial lobule designated as SL2.Our present and previous studies showed that the major divisions of the hypothalamus and thalamus are derived embryonically from distinguishable parts of the third ventricle neuroepithelium. This implies that the third ventricle neuroepithelium has a “mosaic” organization and suggests that the fate of hypothalamic and thalamic neurons may be determined to some extent while their precursors are still prolifer

ISSN:0092-7317    

DOI:10.1002/cne.901880310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901880301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY