摘要:

AbstractAxonal transport methods were used to determine the extent and organisation of neocortical projections from the Suprageniculate (SG) and posterior (PO) thalamic nuclei in the brush‐tailed possum. Our findings show that SG projects extensively to the auditory cortex, overlapping the cortical projection field of the modial geniculatc nucleus, and to the immediately neighbouring association cortex. Though the input relationships of SG appear similar to those reported for other mammals, placental and marsupial, a strong SG projection to auditory cortex has not been reported previously. Neocortical relationships of PO are characterised by an orderly point‐to‐point projection to all but the most rostral parts of the motor‐somaesthetic cortex. There is also a substantial projection to the entire posterior parietal association cortex. The PO‐neocortex projection is reciprocally organised. The PO‐neocortical projection in the possum is similar to that reported in the Virginia opossum, rat, and several other mammals. There is a major difference in organisation in comparison with certain monkeys where the PO projection is much more restricted and does not involve the motor and som‐aesthetic cortex. We conclude that PO is similarly organised in many, though not all, mammals, including the marsupials, rodents, insectivores, and prosimian primates. The possum SG, on the other hand, is clearly distinct from other mammals in its extensive projection to auditory cortex, though we cannot say at present whether this a general property of marsupial mammals or a peculiarity restricted to this species and possibly its cl

ISSN:0092-7317    

DOI:10.1002/cne.902170402

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

年代:1983

数据来源: WILEY

摘要:

AbstractEarlier studies showed that embryonic retina, cortex, or tectum transplanted adjacent to the superior colliculus of newborn host rats differentiated many of the histological features appropriate for the donor region and developed interconnections with the host nervous system. In the study presented here, the same regions were transplanted to the brain of adult host rats and the development of these transplants was compared to those into newborn hosts. Retina, rostral tectum, or occipital cortex was dissected from donor rat embryos on gestational day 14 or 15. A portion of cortex was aspirated in 2‐;menth‐old host rats to expose the right superior colliculus, and one of the donor tissues was placed adjacent to the colliculus in each host. Two to 4 months after transplantation, transplant histology and neuronal interconnections between the transplant and host nervous system were studied by using Nissl and neurofibrillar stains and3H‐proline and HRP tract tracing techniques.Four main points can be drawn from these results. First, 80% of the transplants survived in adult hosts –a percentage comparable to that found in newborn hosts. Second, each of the types of tissues transplanted differentiated histological characteristics appropriate for its site of origin, although the degree of differentiation was always much less than in transplants to newborns. Third, the transplants developed only relatively local projections into the host cortex and superior colliculus. This contrasts with the extensive projections found from the transplants into the brain of newborn hosts. Fourth, no definitive projections from the host retina or brain were identified to any of the transplants into adults, whereas both cortical and tectal transplants into newborns received projections from t

ISSN:0092-7317    

DOI:10.1002/cne.902170403

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

年代:1983

数据来源: WILEY

摘要:

AbstractRetrograde axonal transport techniques were used to identify the afferent connections of the lateral agranular field (AG) of the rat frontal cortex. This cytoarchitectonically distinct cortical field forms the bulk of the primary motor cortex (MI) as defined by intracqrtical microstimulation studies (Donoghue and Wise, 1982). Following injections of horseradish peroxidase (HRP) or wheat germ agglutinin conjugated to HRP into AG1, retrogradely labeled cells are found in the forebrain, thalamus, and brainstem. Within the cerebral cortex labeled neurons are mainly present in the first somatic sensory area (SI), the second somatic sensory area (SII), and the medial agranular field, which lies medial and rostral to AG1. In SI, labeled cells are found primarily in a cytoarchitecturally distinct region called the dysgranular field of SI. Labeled neurons are present in layers II and III, Va, and the deepest part of layer VI in this field and in SII. Labeled cells are also present in layers Va and VI of the densely granular field of SI, which is the part of SI that is strongly activated by cutaneous inputs. Commissural inputs to AG/ arise from layers II‐VI of the contralateral AG1 and thalamic inputs arise from the ventrolateral, ventromedial, posterior medial, and central lateral nuclei. Additional afferent fibers originate from neurons in the basal forebrain, the ventral thalamus, the midbrain raphe nuclei, and the locus coeruleus. This combination of inputs to AG1 from somatic sensory and frontal cortical fields, thalamic motor centers, and several other subcortical areas implies that AG1 forms a subdivision of sensorimotor cortex that is important in centrally directed movements as well as those that are guided by somatic sensory feedbac

ISSN:0092-7317    

DOI:10.1002/cne.902170404

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

年代:1983

数据来源: WILEY

摘要:

AbstractGolgi‐impregnated and methionine‐enkephalin (ME)‐ and substance P (SP)‐immunoreactive neurons were studied throughout the feline nucleus tractus solitarii. The majority of Golgi‐impregnated neurons in the NTS range in size from 5 to 18 μm. A noticeable exception is the large (15–30 μm) neurons of the ventrolateral subdivision. The Golgi‐impregnated neurons possess dendritic trees which remain within the nucleus and even at times within the particular subdivisions. Golgi‐impregnated neurons had a variety of spine forms: pedunculated, sessile, filiform, and complex. A number of neurons exhibited axons originating from the cell and they could be followed for distances up to 100 μm.ME‐ and SP‐immunoreactive neurons were found in commissural, medial, lateral, and parvocellular subdivisions while ME‐immunoreactive neurons were situated additionally in the intermediate and ventrolateral subdivisions. Both types of immunostained neurons were similar in size (6–20 μm) and shape of dendritic arbor. One population of ME‐immunoreactive neurons resembled the large ventrolateral neurons of the Golgi impregnations. Neither type of immunostained neuron possessed the extensive dendritic arbor, numbers of spines, or axons of the Golgi–impregnated neurons. The presence of ME‐ and SP‐immunoreactive neurons in regions which are associated with autonornic regulation suggests that these two pe

ISSN:0092-7317    

DOI:10.1002/cne.902170405

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe present study was conducted to examine the spatial organization of locus coeruleus (LC) neurons that project to rat cerebral cortex. Long‐Evans hooded rats received unilateral pressure injections of horseradish peroxi‐dase (HRP) in either frontal (n = 6) or sensorimotor (n = 11) or occipital (n = 7) cortex to determine the intranuclear location of LC neurons which project to specific neocortical regions. Coronal and sagittal sections (40–100 μm) through the LC were examined by light microscopy after carrying out the tetramethyl benzidine reaction and staining with neutral red. The locations of retrogradely labeled cells were recorded on a three‐dimensional biological coordinate system maintained by a computer linked to the light microscope. LC neurons labeled from cerebrocortical injections of HRP were primarily located in the ipsilateral and to a lesser extent (fewer than 5% of total labeled cells) in the contralateral nucleus. Coeruleocortical projection neurons were concentrated in the caudal three‐fifths of the dorsal division of the ipsilateral LC. Within this portion of the nucleus, HRP‐filled neurons were distributed so that individual groups of cells projecting to occipital or sensorimotor or frontal cortex were coarsely aligned in a dorsal to ventral array, respectively. Moreover, in the sagittal plane of the nucleus the pattern of labeling was spatially graded so that the subset of neurons projecting to the occipital cortex was displaced more caudally in the LC than the groups of cells sending axons to sensorimotor or frontal cortex. Only the frontal area of the cortex received a projection from both dorsal and ventral divisions of the ipsilateral LC. Computer‐assisted analysis of the data further suggested that neocortical projection neurons in the dorsal LC are loosely organized into two groups which run rostrocaudally through the core of the caudal nucleus. The zone of labeling resulting from injections confined to the neocortical gray matter overlapped with but was not coextensive with that observed following injections into the caudate, hippocampus, and cerebellum. These results suggest that partially overlapping subsets of LC cells might independently influence separate populations of neurons within noradrenergic terminal fields of

ISSN:0092-7317    

DOI:10.1002/cne.902170406

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

年代:1983

数据来源: WILEY

摘要:

AbstractIn amphibians, the spinomedullary region of the central nervous system is compressed rostrocaudally because of the absence of a neck. In Ranid frogs, the hypoglossal nerve emerges as the ventral ramus of the second spinal nerve. The first spinal nerve, though present in tadpoles, is absent as a separate nerve in adults. To investigate the central nervous system components of the hypoglossal nerve inRana pipiens, we soaked identified, transected branches of this nerve in horseradish peroxidase, a retrograde and antercgrade tracer. We found that the hypoglossal nerve in these frogs originates from two efferent nuclei located in the caudal medulla, a medial and a lateral one. Afferent fibers, primarily from the tongue, are also found in the hypoglossal nerve and travel in the dorsolateral funiculus of the spinal cord, descending to thoracic levels of the cord. Efferents to intrinsic tongue muscles and the genioglossus muscle originate in the medial medullary nucleus. Efferents to the sternohyoid muscle, which travel through the hypoglossal nerve, originate in the lateral medullary nucleus. Since in mammals the sternohyoid muscle is innervated by the first spinal nerve, we have obtained experimental evidence that the hypoglossal nerve inRana pipienscontains components of this spinal nerve.

ISSN:0092-7317    

DOI:10.1002/cne.902170407

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

年代:1983

数据来源: WILEY

摘要:

AbstractWe describe here the morphology of the inferior olive and the localization of labeled cells after HRP injections into various lobules of vermis and hemisphere of the cerebellum of the sheep. The medial part of the caudal half of the medial accessory olive projects to a medial zone in the anterior lobe, the simple lobule, and the lobules VII and VIII. The lateral part of the medial accessory olive projects to more lateral parts of these lobules with the exception of lobule VII. The group β projects in a differential manner to the lateral parts of the lobules VII and VIII and the medial parts of the lobules IX and X. The dorsomedial cell column projects to lobules VIII, IX, and X; the connections of the dorsal cap are restricted to lobule X.Fibers from the caudal limb of the dorsal accessory olive terminate in the B zone, the simple lobule, and in lobule VIII. The rostral half of the medial accessory olive projects to lobule IX and to the hemisphere. The other projections of the accessory olives and the principal olive to the hemisphere are similar to those reported for the cat. An accessory cell group in the sheep, located between the principal and the dorsal accessory olive, has connections with the caudal vermis and the hemisphere

ISSN:0092-7317    

DOI:10.1002/cne.902170408

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

年代:1983

数据来源: WILEY

摘要:

AbstractRoughly 10% of the neurons in layer, IVah.of cat area 17 accumulate exogenous3H‐gamma‐aminobutyric acid (GABA) but how many types of neuron comprise this population was unknown. We characterized these neurons by partial reconstruction of their somas from serial electron microscope autoradiograms and distinguished four types. GABA 1 was large (>16.5 μm) and dark with a dense distribution of synaptic terminals, substantial geniculate input to the soma, and a moderate accumulation of GABA. GABA 2 was small (<13 μm) and pale, also with a dense distribution of terminals but without evidence of somatic geniculate input, and a moderate accumulation of GABA. GABA 3 was radially fusiform (20μm × 8 μm) with varicose dendrites, a sparse distribution of synaptic terminals, and a heavy accumulation of GAB A. GAB A 4 was medium in size (15 μm) with a moderate distribution of synaptic terminals and a heavy accumulation of GABA. Reasons are presented for believing that each of these four categories of GABA‐accumulating neuron represents a fundamenta

ISSN:0092-7317    

DOI:10.1002/cne.902170409

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe maturation of dendrites in the cat's dorsal lateral geniculate nucleus was studied in Golgi Kopsch preparations of kittens from 3 days to 8 weeks postnatal. During the first postnatal week, more than a month after their birthdate, cells are immature and lack dendrites, bearing only multiple somatic processes or a few short thick extensions. Cells enter an active phase of dendritic extension during the second postnatal week. Growth cone‐like structures and filopodia occur at the ends of dendrites and also at dendritic branch points. Assignment to general cell classes based on dendritic disposition is possible only after this period, and characteristic grapelike appendages are obvious after the third week. Mature cells in the lateral geniculate nucleus are not considered spiny, yet spines and hairs are ubiquitous on most cells once dendrites elongate and remain numerous on peripheral dendrites even after the soma and proximal dendrites become smooth, by 4–6 weeks. The decline of spine levels continues after this period.All cells go through a similar but nonsynchronous sequence of maturation. Large cells may mature first, but no correlation was noted between rate of maturation and laminar location or retinal representation. In the second and thirdpostnatal weeks, although the terminal arbors of retinal axonspre‐synaptic to geniculate cells have already attained their final topography and laminar placement, the shape and synaptic relations of axon terminal swellings remain immature (Mason, 1982a,b) through the most active phase of dendritic outgrowth. After 3 weeks, both retinal axons and target geniculate cell dendrites finalize the shapes of characteristic appendages and synaptic relations in tandem. Potential interactions between immature axon terminal arbors and dendrite‐bare geniculate cells during dendrite outgrowth and subsequent remodeling of structural details are di

ISSN:0092-7317    

DOI:10.1002/cne.902170410

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

年代:1983

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902170401

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

年代:1983

数据来源: WILEY