bluuebunny/crossref_metadata_2025_split huggingface dataset:
Topographical organization of the cortical afferent connections of the prefrontal cortex in the cat
Authors: Cavada Carmen , Reinoso‐Suárez Fernando 
Published: May 2005

AbstractThe topographical distribution of the cortical afferent connections of the prefrontal cortex (PFC) in adult cats was studied by using the retrograde axonal transport of horseradish peroxidase technique. Small single injections of the enzyme were made in different locations of the PFC, and the areal location and density of the subsequent neuronal labeling in neocortex and allocortex were evaluated in each case. The comparison of the results obtained in the various cases revealed that (1) four prefrontal sectors (rostral, dorsolateral, ventral, and dorsomedial) can be distinguished, each exhibiting a particular pattern of cortical afferents. (2) All PFC sectors receive projections from the ipsilateral insular (agranular and granular subdivisions) and limbic (infralimbic, prelimbic, anterior limbic, cingular, and retrosplenial areas) cortices. These cortices provide the most abundant cortical projections to the PFC, and their various subdivisions have different preferential targets within the PFC. (3) The premotor cortex and the following neocortical sensory association areas project differentially upon the various ipsilateral PFC sectors: the portion of the somatosensory area SIV in the upper bank of the anterior ectosylvian sulcus, the visual area in the lower bank of the same sulcus, the auditory area AII, the temporal area, the perirhinal cortex, the posterior suprasylvian area, area 20, the posterior ectosylvian area, the suprasylvian fringe, the lateral suprasylvian area (anterolateral and posterolateral subdivisions), area 5, and area 7. (4) The olfactory peduncle, the prepiriform cortex, the cortico‐amygdaloid transition area, the entorhinal cortex, the subiculum (ventral, posteroventral, and posterodorsal sectors), the caudomedial band off the hippocampal formation and the postsubiculum are the allocortical sources of afferents to the PFC. (5) The dorsolateral PFC sector is the target of the largest insular, limbic, and neocortical sensory association projections. The dorsomedial and rostral sectors receive notably less abundant cortical afferents than the dorsolateral sector. Those to the dorsomedial sector arise from the same areas that project to the dorsolateral sector and are more abundant to the dorsal part, where the medial frontal eye field cortex is located. The rostral sector receives projections principally from all other PFC sectors, and from the limbic and insular cortices. The projections from the allocortex reach preferentially the ventral PFC sector. (6) Intraprefrontal connections are most abundant within each PFC sector. Commissural interprefrontal connections are largest from the site homotopic to the HRP injection. Contralateral heterotopic areas also project to the PFC.The present findings are compared to the patterns of distribution of cortical afferents in the PFC reported in macaque monkeys and similarities and differences are considered.
A quantitative study of the relative contribution of different retinal sectors to the innervation of various thalamic and pretectal nuclei in goldfish
Authors: Springer Alan D. , Mednick Adam S. 
Published: May 2005

AbstractThe contribution of retinal ganglion cells situated in different retinal quadrants to the innervation of eight nontectal, retinorecipient targets was examined in goldfish. In some fish, cobaltous‐lysine was used to selectively fill severed intraretinal ganglion cell axons and the number of filled axons within each nucleus was determined. In other fish, either the dorsal or ventral or nasal or temporal retina was ablated and the remaining axons from the intact retina were filled with cobalt. The density of the cobalt‐filled axons within the retinorecipient targets was quantified with a microdensitometer. All of the eight targets received different degrees of innervation when the contributions from dorsal and ventral retina were compared. The suprachiasmatic nucleus received axons from ventral, but not from dorsal, retinal ganglion cells (RGCs), while the nucleus opticus dorsolateralis, nucleus opticus commissurae posterior, and nucleus opticus pretectalis dorsalis received more axons from ventral than from dorsal RGCs. The tuberal region, nucleus corticalis, and the accessory optic nucleus received axons from dorsal, but not from ventral, RGCs. The nucleus opticus pretectalis ventralis received more axons from dorsal then from ventral RGCs. Only one target, nucleus corticalis, appeared to receive more axons from nasal than from temporal RGCs. In general, those nuclei that were closest to the dorsal optic tract were innervated exclusively or predominantly by ventral RGC axons, whereas those nuclei that were closest to the ventral optic tract were innervated exclusively or predominantly by dorsal RGC axons. These data indicate that in this particular vertebrate, the dorsal and ventral retinal regions are not homogeneous with respect to their projections to nontectal nuclei. The possible role that the nontectal nuclei play in determining the course of optic axons is discussed.
Pattern of rat olfactory bulb mitral and tufted cell connections to the anterior olfactory nucleus pars externa
Authors: Scott John W. , Ranier Elizabeth C. , Pemberton Janice L. , Orona Edward , Mouradian Laurie E. 
Published: May 2005

AbstractThe pattern of output of mitral and tufted cells of the rat olfactory bulb (OB) to layer Ia overlying the pars externa (pE) of the anterior olfactory nucleus (AON) has been studied in the rat by iontophoresis of horseradish peroxidase and Phaseolus vulgaris‐leucoagglutinin. These agents labeled mitral and tufted cells and at least the proximal portion of their axons. In most cases we observed small branches from axons of the lateral olfactory tract that appear to terminate in the region of the pE AON, while the main axon could often be traced for considerable distances past these branches. These branches are assumed to terminate in the pE AON because they could not be traced to other terminal regions, because they ramify in layer Ia, and because they usually show small swellings characteristic of axons in terminal regions. Although each ramification could be extensive, we found that the positions of these small branches were related to the positions of the injections within the OB. Dorsal medial injections labeled dorsal branches. Ventral medial injections labeled ventral branches. Injections on the lateral face of the OB labeled intermediate branches. The centers of the regions within which branches were labeled were strongly correlated with the positions of the injection around the circumference. Comparison of the anterior‐posterior axis of the OB produced no such strong correlation. Reconstructions of axons showed that terminal branches arise from both mitral and tufted cells, although at least some mitral cells are shown not to have such branches in the pE AON.Studies of the patterns of dendrites and terminals in the pE AON indicate that this region has the same pattern of layer Ia and Ib terminals seen in other olfactory cortical regions. The pE AON cell layer is intercalated just below the boundary between layers Ia and Ib. Since dendrites of the underlying pars lateralis of the AON (pL AON) penetrate into layer Ia over much of the pE AON, it is necessary to remember that at least part of the pL AON may also receive topographically organized inputs.
The primate mediodorsal (MD) nucleus and its projection to the frontal lobe
Authors: Goldman‐Rakic Patricia S. , Porrino Linda J. 
Published: May 2005

AbstractThe frontal lobe projections of the mediodorsal (MD) nucleus of the thalamus were examined in rhesus monkey by transport of retrograde markers injected into one of nine cytoarchitectonic regions (Walker's areas 6, 8A, 9, 10, 11, 12, 13, 46, and Brodmann's area 4) located in the rostral third of the cerebrum. Each area of prefrontal, premotor, or motor cortex injected was found to receive a topographically unique thalamic input from clusters of cells in specific subdivisions within MD. All of the prefrontal areas examined also receive topographically organized inputs from other thalamic nuclei including, most prominently, the ventral anterior (VA) and medial pulvinar nuclei. Conversely, and in agreement with previous findings, MD projects to areas of the frontal lobe beyond the traditional borders of prefrontal cortex, such as the anterior cingulate and supplementary motor cortex. The topography of thalamocortical neurons revealed in coronal sections through VA, MD, and pulvinar is circumferential. In the medial part of MD, for example, thalamocortical neurons shift from a dorsal to a ventral position for cortical targets lying medial to lateral along the ventral surface of the lobe; neurons in the lateral MD move from a ventral to a dorsal position, for cortical areas situated lateral to medial on the convexity of the hemisphere. The aggregate evidence for topographic specificity is supported further by experiments in which different fluorescent dyes were placed in multiple areas of the frontal lobe in each of three cases. The results show that very few, if any, thalamic neurons project to more than one area of cortex. The widespread cortical targets of MD neurons together with evidence for multiple thalamic inputs to prefrontal areas support a revision of the classical hodological definition of prefrontal cortex as the exclusive cortical recipient of MD projections. Rather, the prefrontal cortex is defined by multiple specific relationships with the thalamus.
Neuronal classes and their relation to functional and laminar organization of the lateral geniculate nucleus: A Golgi study of the prosimian primate, Galago crassicaudatus
Authors: Conley Michael , Birecree Elizabeth , Casagrande V. A. 
Published: May 2005

AbstractThe neuronal organization of the lateral geniculate nucleus of the prosimian primate, Galago crassicaudatus, was studied in Golgi‐Kopsch‐impregnated material. On the basis of cytoarchitecture, electrophysiology, and connections the nucleus is divisible into three pairs of layers—one magnocellular, one parvocellular, and one koniocellular—each part of a separate retinogeniculate and geniculostriate pathway (Itoh et al., '82; Norton and Casagrande, '82).In Macaca and Saimiri, which have equally distinct geniculate subdivisions, it has been reported that, outside of cell size, no one morphological attribute differentiates magnocellular from parvocellular neurons (Campo‐Ortega et al., '68; Wong‐Riley, '72; Saini and Garey, '81; Wilson and Hendrickson, '81). Results presented here are not inconsistent with this conclusion. However, when the results are analyzed from the standpoint of the collective traits that distinguish the cell groups that make up the layers, clear morphological differences are evident.Using this approach we find the following differences between presumed projection neurons and interneurons in each pair of layers. The projection neurons of the magnocellular layers, as a group, exhibit large cell bodies with radially arranged dendrites which often extend beyond laminar borders. The magnocellular interneurons are larger than their counterparts in the other layers and, like the magnocellular projection neurons, exhibit radially arranged dendrites. The former, however, also share characteristics in common with other interneurons such as relatively small somata, few proximal dendrites, and complex distal dendritic appendages. In contrast, the projection neurons and interneurons of the parvocellular layers have smaller somata and more restricted dendritic spreads than their counterparts in the magnocellular layers. Dendritic arbors of parvocellular neurons are typically oriented perpendicular to laminar borders and remain confined to their layer of origin. The koniocellular neurons represent a more diverse population but collectively are distinct in that the dendrites of almost all neurons in these layers run parallel to the layers.The fact that presumed interneurons and projection neurons in a single layer share a number of related dendritic features suggests that both groups together are responsible for the structural and, hence, functional architecture of a layer. We conclude that when the organization of the lateral geniculate nucleus is considered from the standpoint of layers and not individual cell types, the functional differences between layers indicated bydifferential connections, histochemistry, and electrophysiology can be related to distinct morphological differences singular to magnocellular, parvocellular, and koniocellular divisions.
Laminar organization of geniculocortical projections in Galago senegalensis and Aotus trivirgatus
Authors: Diamond I. T. , Conley M. , Itoh K. , Fitzpatrick D. 
Published: May 2005

AbstractThe projections of the lateral geniculate nucleus to striate cortex were traced by anterograde and retrograde transport of WGA‐HRP in two primates, Galago and Aotus. The goal was to determine the laminar organization of the terminals of individual layers of the lateral geniculate nucleus. The results show that in both species the magnocellular layers project to cortical layer IVα, the parvicellular layers project to IVβ, and the intercalated geniculate layers (which term includes layers 4 and 5 in Galago) project to layers III and I. The distribution of terminals in layer III is periodic, which is to say, there are regularly spaced regions of terminals separated by regions devoid of terminals. When the two species are compared to Saimiri, it is clear that the basic organization of the three pathways relaying in the lateral geniculate nucleus is common to all three primates. At the same time, there are some significant species differences. The total pattern of projections in Galago is compressed in comparison to that in the monkey, and this compression seems to be related to the poorer differentiation of cortical layers in the prosimian. For example, layer IIIC is distinct only in the two monkeys and at the same time it is spared from geniculate terminations. Both Galago and Aotus differ from Saimiri in that they lack a projection from the parvicellular geniculate layers to the layer IIIB. These species comparisons are relevant to the questions of the functional significance of the three pathways and the evolution of the primate striate cortex.
The ultrastructure of enkephalin‐immunoreactive neurons in the interpeduncular nucleus of the rat
Authors: Mahalik Thomas J. , Finger Thomas E. 
Published: May 2005

AbstractThe interpeduncular nucleus of the rat is a complex structure, displaying diverse immunocytochemical and ultrastructural features. This nucleus contains opiate receptors, enkephalin‐positive cell bodies and enkephalin‐positive fibers. The ultrastructure of rat interpeduncular enkephalinergic neurons has not been described, nor has the role that these neurons play in the internal organization of the interpeduncular nucleus been established. The purpose of the present study was to describe the ultrastructure of enkephalinlike‐immunoreactive (ELI) cells with particular emphasis on the subnuclear organization of their dendritic and terminal fields.Enkephalinlike‐immunoreactive (ELI) cell bodies are present in the rostral and apical subnuclei of the interpeduncular nucleus (IPN), but are absent from the other subnuclei of the IPN. The rostral subnucleus also contains immunoreactive dendrites that are postsynaptic to nonreactive terminal boutons. Numerous ELI axon terminals were observed in the central and intermediate subnuclei. The results of our study suggest that enkephalinergic interneurons link the rostral IPN with more caudal regions of this nucleus.
Glutamic acid decarboxylase and somatostatin immunoreactivities in rat visual cortex
Authors: Lin Chia‐Sheng , Lu S. M. , Schmechel D. E. 
Published: May 2005

AbstractAntibodies to glutamic acid decarboxylase (GAD) and somatostatin (SS) were used to determine the laminar distribution and morphology of GAD‐and SS‐immunoreactive neurons and terminals in rat visual cortex. The present study demonstrates that GAD‐immunoreactive neurons constitute several morphologically distinct subclasses of neurons in rat visual cortex. These subclasses of neurons can be distinguished by differences in soma size, soma shape, dendritic branching patterns, axonal arborizations, and location in the neuropil.GAD‐immunoreactive neurons are found throughout all layers of visual cortex. They have nonpyramidal morphology and constitute roughly 15% of the total neuronal population. The laminar pattern of GAD‐immunoreactive puncta is uneven, with a prominent band of terminals in layer IV. Numerous large GAD‐positive puncta surround the somata and proximal dendrites of pyramidal cells in layers II, III, and V.SS‐immunoreactive neurons constitute a less numerous and more restricted population of nonpyramidal neurons. Their somata are located mainly in layers II, III, V, and VI. Very few, if any, SS‐immunoreactive neurons are found in layers I and IV. SS‐immunoreactive terminals are arranged along vertical and diagonal collateral branches that have a beaded appearance.Finally, many neurons in the supra‐ and infragranular layers and in the white matter are immunoreactive to both glutamic acid decarboxylase and somatostatin. This coexistence of immunoreactivity to both GAD and SS may characterize a broad subclass of cortical nonpyramidal neurons.
Axonal growth cones in the developing amphibian spinal cord
Authors: Nordlander Ruth H. 
Published: May 2005

AbstractAxonal growth cones in the spinal cord of embryonic and larval Xenopus (stages 24–48) were filled with the anatomical tracer horseradish peroxidase (HRP). Growth cones of lateral and ventral marginal zones, including those of descending spinal and supraspinal pathways, were labeled by application of tracer to the caudal medulla or to one of several levels of the spinal cord. Central axons of sensory neurons were filled via their peripheral processes. Growth cone configuration varied widely but fell into five general categories: complex with both filopodia and veils, filopodia only, lamellipodia only, clavate, and fusiform. Several general patterns emerged from the distribution of these various configurations. Growth cones of younger animals generally were more complex than those of older ones. Growth cones closer to the leading edge of descending fiber bundles were more elaborate than those that followed. Growth cones of the dorsolateral fascicle, which carries ascending central processes of Rohon‐Beard and sensory ganglion neurons, were very simple and followed a straight course rostrally, whereas those of descending axons of the lateral fiber areas were more complex and sometimes spread over almost the entire lateral marginal zone. Growth cones of Rohon‐Beard central ascending axons were fusiform or clavate, while those of sensory ganglion axons showed several fine filopodia at their tips. Growth cones of both types of sensory axons change configuration as they approached the hindbrain, becoming more complex. This study demonstrates that the configurations of growth cones belonging to the same axonal pathway vary with age and with position along their routes, and that growth cones of different neuron classes exhibit characteristic ranges of morphological variation.
Synapse formation in the olfactory cortex by regenerating optic axons: Ultrastructural evidence for polyspecific chemoaffinity
Authors: Scalia Frank 
Published: May 2005

AbstractThe optic nerve was severed at its entry into the optic chiasma and implanted into the striatal region of the ipsilateral cerebral hemisphere in adult frogs (Rana pipiens). Regenerating retinal ganglion cell axons, observed by the autoradiographic tracing method and by horseradish peroxidase (HRP) fiber filling, grew anteriorly along the olfactory tracts and posteriorly along the ipsilateral lateral forebrain bundle and stria medullaris. Many of the regenerating axons ultimately joined the ipsilateral optic tract. The optic axons formed terminal plexuses in the olfactory cortex, lateral geniculate complex, pretectum, tectum, and basal optical nucleus but not in the amygdala or other cerebral territories not postsynaptic to the olfactory bulb, nor in the cell groups associated with the lateral forebrain bundle or stria medullaris. Optic axon terminals labeled with HRP were observed by electron microscopy in the ipsilateral olfactory cortex and in the normal projection areas of the optic nerve, although they were misplaced to the ipsilateral side. They contained clear, spherical synaptic vesicles and pale mitochondria and made Gray type I, asymmetric contacts on dendrites. The retinal projection to the olfactory cortex was formed early in regeneration and was maintained to some degree for periods up to 39 weeks. It was absent in a specimen surviving 50 weeks. Retinal innervation appeared earlier in the lateral geniculate complex and pretectum than in the tectum.These observations suggest that regenerating retinal ganglion cell axons have an affinity for neurons in the olfactory cortex, as well as for the neurons in the optic pathway to which they are normally postsynaptic. Unless the apparent selectivity of the aberrant projection is regulated by principles other than those that bring about the reinnervation of the normal optic centers, the data further suggest that the nature of the molecular mechanisms conveying synaptic specificity must be broad enough to permit the formation of limited sets of alternative synaptic connections. The ability to innervate selectively targets other than those normally specified is termed, here, polyspecificity. Since polyspecificity refers to the the affinity of retinal ganglion axons, as a class, for target, structures considered as unit aggregates, it is conceptually different from the graded affinity of ganglion cells in different regions of the retina for target neurons in different regions of the tectum. Hierarchically interactive mechanisms capable of regulating the expression of affinity molecules during development are discussed as a means for restricting the formation or stabilization of nonstandard connection hypothetically made possible by polyspecificity.