摘要:

AbstractThe organization of local projections within the rat primary visual cortex (area 17) was investigated by tracing fibers with HRP in in vitro brain slices. The projections from different layers showed distinct laminar patterns. Layer 4 made a strong, topographically precise, projection to lower layer 2/3; weaker projections extended laterally and terminated diffusely in layer 2/3 but also ran vertically to layers 5 and 6. The connections of lower and upper layer 2/3 were reciprocal and point‐to‐point. Within layer 2/3, a large number of fibers ran horizontally and terminated at variable distances from the injection site without making terminal clusters. The main output from layer 2/3 was to layer 5. The most prominent projections from the upper half of layer 5 were to layers 2/3 and 6; lower layer 5, in contrast, made wide‐ranging, clustered projections to layer 1, the bottom of layer 2/3, and the top of layers 4 and 5. The patches were 130–160 μm wide and spaced apart by 230–260 μm. The main projection that arose from the superficial layer 6 terminated in layer 4 above the injection site. In contrast, lower layer 6 made clustered projections to the layer 3/4 border, extending up to 2 mm in the coronal plane. The patches were 190–220 μm wide and spaced apart by 320–390 μm. Additional projections went to the layer 5/6 border and layers 1 and 2.These results indicate that geniculocortical input is processed through interlaminar connections that are topographically precise, widespread, or patchy. These connectivity patterns suggest a role for these connections in the transformation of functional maps between layers; focused projections preserve the architecture of the layers of origin, and diverging or patchy projections rearrange this organization and form new maps in the target layers (Lund:Annu. Rev. Neurosci. 11:253–288, '88). However, only a few interlaminar connections show one of these patterns in isolation, making it difficult to assign a single function to a particular connection. We, therefore, tentatively conclude that projections terminating in layers 1–4, with the possible exception of the connection between upper layer 6 and layer 4, transform functional maps. In contrast, the topographically precise projections from upper to lower layers preserve functional maps. The specific role of these connections in the construction of receptive field properties, however, is not known. But it is interesting that some of these local connections are clustered and show an organization which is a common feature of intracortical connections in species with a columnar organiza

ISSN:0092-7317    

DOI:10.1002/cne.902790202

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractWe have previously reported that a proportion of ganglion cells die during optic nerve regeneration in the adult frogHyla moorei(Humphrey and Beazley, '85). Here we assess the effect of preventing optic nerve regeneration on this cell loss. The optic nerve was crushed unilaterally and regeneration was allowed to progress unimpeded in one experimental series but was prevented by ligating or capping the nerve in another.We estimated total cell numbers in the ganglion cell layer from cresylstained wholemounts, comparing each experimental retina with its unoperated partner. At 70–78 days postcrush, mean cell numbers had fallen by 31.5% for frogs with unimpeded regeneration (N = 9), a significantly greater reduction than the 21.5% (N = 8) loss for the impeded regeneration series (p<0.001). Thereafter, cell numbers were stable for frogs with unimpeded regeneration. Cell death continued in the series with impeded regeneration, and losses exceeded those of frogs with unimpeded regeneration from 110 days postcrush. When regeneration was impeded, ganglion cell somas underwent an intense cell soma reaction and became arranged in rows radiating from the optic nerve head.Our findings indicate that some ganglion cells are transiently spared when regeneration of their axons is prevented. The abnormally extensive contacts formed between somas may delay ganglion cell loss. However, the eventual death of most ganglion cells shows them to be target‐independent in the long t

ISSN:0092-7317    

DOI:10.1002/cne.902790203

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractTransganglionic degeneration and transganglionic transport of HRP were used for investigation of the spinal cord and brainstem projections from the superficial, cutaneous (SR) and deep, muscular (DR) branches of the radial nerve. The HRP study included a numerical and size analysis of labelled dorsal root ganglion (DRG) cells.In degeneration experiments the SR nerve was found to project somatotopically to laminae III–IV, but degeneration was also found in lamina I and inconsistently in lamina II. Transection of the DR nerve was found to give rise to a small amount of degeneration, which in “sham” operations was established to result from the skin injury during dissection of the DR nerve.With the HRP method, the SR nerve was found to project somatotopically to laminae I–IV, whereas the DR nerve projected more diffusely to the medial part of laminae V–VII. HRP application to the SR and DR nerves resulted in labelling of a mean of 1,024 and 310 DRG cells, respectively. These labelled neurons had a median cell area of 381 and 562 μm2for the SR and DR nerves, respectively, and both small and large cells were labelled in both types of experiments. In the lower brainstem, projections from the SR nerve were found only in the ipsilateral dorsal part of the main cuneate nucleus (MCN) with both methods. Brainstem projections from the DR nerve that were found only with the HRP method were found in the ipsilateral ventral part of the MCN together with a projection to the ipsilateral external cuneate nucleus. No projections were found to the central cervical nucleus.The present results indicate that cutaneous compared to muscular primary sensory neurons are much more prone to react with transganglionic degeneration after peripheral nerve transection. Furthermore, in the rat the SR nerve projects somatotopically, whereas the DR nerve does not. Both nerve branches are connected to small and large spinal ganglion cells, although the median cell area is larger in muscul

ISSN:0092-7317    

DOI:10.1002/cne.902790204

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe Van der Loos modification of the Golgi‐Cox method and morphometric analyses were used to study the neuronal types in the striatum of adult (3, 6, and 10 months) and aged (20, 25, and 30 months) C57BL/6N mice. In adult mice six types of striatal neurons were distinguished primarily on the basis of the morphology of their cell body and dendrites. Each of these types was compared with morphologically similar neurons from previous Golgi classifications in other species and discussed within the framework of recent immunocytochemical work.With similar methods the age‐related changes occurring on the dendrites of three of the six striatal types were also analyzed. In the mediumsized neuron with spine‐laden dendrites, various dendritic tree shapes and sizes were distinguished in all age groups studied. Qualitative observations as well as measurements of total dendritic length per cell suggested that the dendrites in this type may both grow and regress throughout the life span, although signs of dendritic atrophy and regression were observed only in the aged groups. In the other two types of neuron, one a medium aspiny cell with thin varicose dendrites and the other a large spiny neuron with many dendrites, measurements of total dendritic lengths revealed sustained growth of the tree well into advanced age, followed by moderate regression in the oldest groups. The present findings also indicate that the dendrites of each type of striatal neuron follow unique temporal patterns of growth and regression during the life span of the

ISSN:0092-7317    

DOI:10.1002/cne.902790205

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe number of neurons per mm3of tissue (number per volume) and the number under 1 mm2of cortical surface (number per column) have been estimated for each lamina of seven cytoarchitectural areas of the cat cortex by using a method of size frequency distribution. The areas studied consisted of four visual areas (the binocular and monocular portions of area 17: 17B and 17M; area 18; and the posteromedial lateral suprasylvian area: PMLS), a somatosensory area (3B), and two motor areas (4γ and 6aα).For both series of measurements, significant differences could be demonstrated among the seven areas studied (one‐way ANOVA;P<.001). The number of neurons pervolumein the binocular and monocular regions of area 17 (≈︁ 49,000/mm3) is 85% greater than that of each of the other regions (≈︁ 27,000) with aP<.01 on an a posteriori Tukey test, but there are no significant differences between the latter areas. The number of neurons percolumnis greater in the binocular portion of area 17 (78,000 under 1 mm2of cortical surface) than in any other area (P<.01). Other sensory areas (17M, 18, PMLS, and 3B) have fewer neurons per column (P<.01) and the numbers do not vary significantly between these regions (range from 56,100 to 61,900). Areas 4γ and 6aα have still fewer neurons ( ≈︁ 44,000;P<.01, exceptP<.05 when compared to PMLS). Thus, the seven areas studied fall under three different categories. Motor areas have the smallest number of neurons per column, sensory areas have more, and the greatest number is found in the binocular region of area 17. It appears that these differences are principally (but not exclusively) due to variations in the number of neurons in layer IV: These variations are largely responsible for the differences that we have found between the binocular portion of area 17 and other sensory areas as well as between the binocular portion of area 17 and other sensory areas as well as between the latter and motor areas. We thus cannot confirm the view of Rockel et al. (Brain 103:221–244, ';80) that there is a basic uniformity of the number of neurons per unit of cortical surface in different cortic

ISSN:0092-7317    

DOI:10.1002/cne.902790206

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractPrevious studies indicate that the distribution of corticoamygdaloid neurons in the rat prelimbic (PL) and infralimbic (IL) cortices overlaps with the distribution of neurons projecting to the contralateral medial prefrontal cortex (MPC), insular cortex, mediodorsal thalamus, and dorsal medulla. In view of the poorly differentiated cytoarchitecture of PL and IL, and their designation as cortical regions transitional between the allocortex and isocortex, the present study sought to determine whether several cortical and subcortical projections from these areas arise as collaterals of corticoamygdaloid neurons. Injections of the fluorescent dyes Fast Blue (FB) or bisbenzimide (BB) were made into the amygdaloid complex and the following areas: agranular and granular insular cortices; mediodorsal thalamic nucleus (MD); nucleus tractus solitarii/dorsal medulla (NTS); contralateral amygdaloid complex; and ipsilateral and contralateral MPC. Neurons projecting to the ipsilateral amygdaloid complex were located mainly in layers II and V with fewer cells in layer III. Concomitant injections into the insular cortex, MD, and NTS labeled populations of neurons arranged in laminae that partially overlapped with, but were essentially separate from, corticoamygdaloid neurons. Projections to the insular cortex arose from layers II and V; those to MD arose from layers V and VI. Corticobulbar projections from IL originated from neurons arranged in a thin lamina in the deep part of layer V. Very few neurons projecting to both the amygdaloid complex and any of these areas were observed. Bilateral injections of FB and BB into the amygdaloid complex producted very few double‐labeled cells in PL and IL. Further, in layer V, ipsilaterally projecting corticoamygdaloid neurons tended to be located more deeply than contralaterally projecting neurons. Combined injections of BB and FB into the amygdaloid complex and the contralateral (but not ipsilateral) MPC resulted in significant numbers of double‐labeled neurons in layers II, III, and V of PL and IL. Control injections of fluorescent dyes into the cerebrospinal fluid labeled few neurons in the superficial layers of PL and IL and a combined injection into the amygdaloid complex (FB) and subarachnoid space (BB) resulted in a very small number of double‐labeled cells in layer II only. The results suggest that a significant proportion of neurons in PL and IL projecting to the amygdaloid complex issue collaterals innervating the contralateral MPC. Evidence is discussed that suggests that the interhemispheric collaterals of MPC corticoamygdaloid neurons may serve to correlate the amygdaloid outputs of the MPC bilate

ISSN:0092-7317    

DOI:10.1002/cne.902790207

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe organization of the cortical monoamine systems, dopamine (DA), and noradrenaline (NA), which have been studied extensively in the rat and more recently in the monkey, had not yet been investigated directly in the human brain. We report here the first systematic account of the regional and laminar distributions of the catecholamine fibers in the human cerebral cortex, using immunohistochemistry of the catecholamine biosynthetic enzymes, tyrosine hydroxylase (TH), and dopamine‐β‐hydroxylase (DBH) in 13 cytoarchitectonic areas (4, 6, 9, 3b, 5, 40, 17, 18, 23, 24, 29, insula, and hippocampus) sampled postmortem.The noradrenergic (NA) innervation, mapped with DBH‐immunoreactivity (DBH‐IR), displayed a characteristic density gradient in the neocortex (highest in the primary sensorimotor areas, decreasing rostrally and caudally) that contrasted with the more uniform density in the limbic cortices (24, 23, 29, insula, hippocampus). NA axons were present in all cortical layers and were least numerous in layer I. The DBH‐IR fibers were only partly TH‐immunostained (10–50%, on double‐labeled sections), suggesting a heterogeneity of the cortical NA axons.The putative dopaminergic (DA) fibers were identified by comparing alternate or double‐immunolabeled (DBH‐TH) sections, as the TH‐IR fibers which contain no DBH‐IR. A DA‐like innervation was present in all cortical areas, with major regional differences in density and laminar distribution, which closely paralleled cytoarchitectural buildups: (1) the DA‐like innervation was densest in the agranular areas, primary and secondary motor areas, anterior cingulate, and insula; it distributed throughout layers I–VI; (2) density was lower in the granular cortices, areas 9 (prefrontal cortex), 23, 3b, 5, 40, and 18, displaying a bilaminar pattern in layers I and V–VI. In all areas, DA‐like fibers were most abundant in the molecular layer, with a predominant distribution in its deepest part. Convoluted and coily fibers represented a unique morphologic aspect of the CA innervation in the human cortex.These findings are in agreement with findings in nonhuman primates and demonstrate major evolutionary changes in the organization of the cortical aminergic input as compared with rodents. The most striking features are the expansion of the DA innervation to the whole cortex and the peak of highest density in the motor areas. The regional differentiation of NA innervation is also accentuated. Slight differences were found in the laminar distributions of the amines in humans and primates. These data seem quite promising and open new research fields in n

ISSN:0092-7317    

DOI:10.1002/cne.902790208

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe motor innervation of the major flight muscles powering the fore‐ and hindwings of the cricketTeleogryllus oceanicuswas investigated. The morphology of the motor neurons was determined by filling them via their axons in the periphery with either Lucifer Yellow or cobalt chloride followed by silver intensification. Details of the location of branches of motor neurons within the ganglion were obtained by serially sectioning ganglia containing filled neurons. For each flight muscle at least two motor neurons were found. The somata of motor neurons were located in two clusters in the ganglion, the anterior lateral cluster and the posterior lateral cluster. Motor neurons in the same cluster had similar morphologies. Most of the arborizations of these motor neurons were in the dorsal neuropil with a few branches in the lateral intermediate neuropil. The morphology of flight motor neurons was compared with the morphology of leg motor neurons in consideration of the possible functional organization of the ganglion. A comparison was made between motor neurons innervating homologous muscles of the cricket and the locust to determine the extent of the difference between the flight systems of these two group

ISSN:0092-7317    

DOI:10.1002/cne.902790209

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractPrevious histochemical studies have suggested that reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase exists in distinct subsets of neurons that neither belong to a single transmitter type nor embrace all the neurons using a single transmitter. As a step toward establishing the role of this enzyme, the distribution of NADPH‐diaphorase‐positive neurons and fibers in the cat central nervous system was mapped by using a direct histochemical method.Heavily stained NADPH‐diaphorase‐positive neurons with many prominent cell processes were observed in the cerebral cortex, white matter, caudate nucleus, putamen, nucleus accumbens, septal nucleus, amygdala, anterior, lateral and posterior hypothalamic areas, dorsolateral part of the periaqueductal gray, superior colliculus, central tegmental field (Berman) (pedunculopontine tegmental area), dorsal tegmental nucleus, nucleus coeruleus, mesencephalic and pontine reticular formation, gigantocellular and magnocellular tegmental fields, nucleus facialis, and motor nucleus of the vagus. Moderately stained neurons with two or three prominent cell processes were observed in the nucleus of the diagonal band of Broca, globus pallidus, and substantia innominata. Medium‐size, moderately stained neurons that had round large nuclei and no visible cell processes were found in the subthalamic nucleus, pontine gray, trapezoid body, and infratrigeminal, cochlear, and vestibular nuclei. Very dense NADPH‐diaphorase‐positive nerve terminal fields were seen in the olfactory tubercle, cortex, caudate nucleus, putamen, dentate gyrus, and interpeduncular nucleus. Intensely stained NADPH‐diaphorase‐positive nerve fibers were found in the stria terminalis, marginal region of the central tegmental field, dorsal tegmental nucleus, and spinal trigeminal tract as well as around the brachium conjunctivum. Although the staining of neurons and tracts was highly selective, they did not correspond to any single known neuronal or neurotransmitter type. Positive staining occurred in discrete subsets of neurons known to be associated with a variety of peptides and classical neurotransmitters. The functional significance of high NADPH diaphorase ac

ISSN:0092-7317    

DOI:10.1002/cne.902790210

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractConnections of a telencephalic vocal‐control nucleus, the lateral magnocellular nucleus of the anterior neostriatum (lMAN), were studied in adult male zebra finches. Anterograde transport of horseradish peroxidase (alone or conjugated to wheat germ agglutinin) revealed that neurons in lMAN project to another forebrain song‐control nucleus, the robust nucleus of the archistriatum (RA). RA is known to project onto the hypoglossal motor neurons that innervate the vocal organ. Retrograde transport of HRP from lMAN labeled a large thalamic nucleus, the medial portion of the dorsolateral nucleus of the thalamus (DLM). DLM in turn receives input from another nucleus of the song‐control system, area X of the parolfactory lobe. We confirmed results of previous studies showing that area X receives a projection from the ventral area of Tsai (AVT) in the midbrain. In addition, we replicated results of previous experiments with canaries showing that the song‐control nucleus HVc (caudal nucleus of the ventral hyperstriatum) receives input from three sources: the medial magnocellular nucleus of the anterior neostriatum (mMAN), the interfacial nucleus (NIf), and the uvae‐form nucleus (Uva) of the thalamus. HVc neurons project to area X and to RA. In summary, there is a path from AVT in the midbrain, to area X, to DLM, and then to lMAN; HVc projects to X and hence indirectly to lMAN. We do not yet know the afferent connections of AVT. Thus, lMAN receives indirect input from a variety of other sources, including other regions known to be involved with voca

ISSN:0092-7317    

DOI:10.1002/cne.902790211

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY