bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organization of retinogeniculate projections in turtles of the genera Pseudemys and Chrysemys
Authors: Ulinski Philip S. , Nautiyal Jaishanker 
Published: January 2005

AbstractOrganization of retinal projections to the dorsal lateral geniculate complex in turtles has been studied by means of light and electron microscopic axon tracing techniques.Orthograde degeneration studies with Fink‐Heimer methods following restricted retinal lesions show the entire retina has a topologically organized projection to the contralateral dorsal lateral geniculate complex. The nasotemporal axis of the retina projects along the rostrocaudal axis of the geniculate complex; the dorsoventral axis of the retina projects along the dorsoventral axis of the geniculate complex. The projection to the ipsilateral dorsal lateral geniculate complex originates from the ventral, temporal and nasal edges of the retina. The nasotemporal axis of the ipsilateral retina projects along the rostrocaudal axis of the geniculate complex. It was not possible to determine the orientation of the dorsoventral axis of the ipsilateral retina on the geniculate complex.Light microscopic autoradiographic tracing experiments and electron microscopic degeneration experiments show the retinogeniculate projection has a laminar organization. Retinogeniculate terminals are found in both the neuropile and cell plate throughout all three subnuclei of the dorsal lateral geniculate complex but have a distinctive distribution in each sub‐nucleus. In the subnucleus ovalis, they are frequent in both the neuropile and cell plate which forms the rostra1 pole of the complex. In the dorsal subnucleus, they are most prevalent in the outer part of the neuropile layer, less frequent in the inner part of the neuropile, and rare in the cell plate. In the ventral subnucleus, they are frequent in the outer part of the neuropile but are also common in the inner part of the neuropile and cell plate.These observations point to several principles of geniculate organization in turtles. First, the complex receives projections from the entire contralateral retina and a segment of the ipsilateral retina. It thus has monocular and binocular segments that together receive a topologically organized representation of the binocular visual space and the contralateral monocular visual space. Second, the three geniculate subnuclei receive information from different, specialized regions of the retina and visual space. Subnucleus ovalis receives information from the frontal binocular visual field. The ventral subnucleus receives information from the caudal binocular field. The dorsal subnucleus receives input from the contralateral monocular field. Third, there is a lamination of retinal inputs in the geniculate complex which differs in character within the three subnuclei. It apparently results in particular distributions of retinal and cortical inputs along the receptive surfaces of geniculate neurons.
Connections of area 8 with area 6 in the brain of the macaque monkey
Authors: Arikuni Tomio , Watanabe Kyoko , Kubota Kisou 
Published: January 2005

AbstractThe corticocortical connections between the arcuate area (Walker's areas 8A and 45 or Brodmann's area 8) and the premotor and supplementary motor areas (Vogts' area 6) in the brain of the macaque monkey were studied microscopically with wheat germ agglutinin‐conjugated horseradish peroxidase (WGA‐HRP), which was injected into Brodmann's area 8 primarily to elucidate the projections of area 8 into area 6. In addition, in the same material, the pattern of connections between the arcuate area and area 46 of the prefrontal cortex was studied. On the basis of the findings of the present study, an anatomical cortical hierarchy for areas 8, 6, and 46 is discussed.Anterogradely labeled axon terminals and retrogradely labeled cells appeared in the premotor area, in the supplementary motor area, and in area 46 on the side of injection; sites containing labeled axon terminals also contained labeled cells. In other words, the examined connections were reciprocal. In the labeled areas, labeled terminals and cells coexisted, and most formed radial columns. However, no labeling of cells and terminals was seen in the motor area (Brodmann's area 4).After injection of WGA‐HRP into area 8A, labeled terminals and cells appeared predominantly in the superior premotor area (a region of the premotor area above the arcuate spur, Vogt and Vogt's upper areas 6aα and 6aß), forming one, two, or three bands of label in the anteroposterior direction, whereas labeling occurred to a lesser extent in the inferior premotor area (a region of the premotor area below the arcuate spur, Vogt and Vogt's areas 4c, lower 6aα and 6b). In contrast, injection of WGA‐HRP into area 45 resulted in the predominant labeling of the inferior premotor area with scant labeling in the superior premotor area.In the premotor area, labeled terminals were distributed over the entire cortical depth, although few were found in the lower half of layer III, and labeled cells were distributed mainly in layer III. In area 46 of the banks of the principal sulcus in the prefrontal cortex, labeled terminals were distributed in all cortical layers or over the entire cortical depth with a lower concentration in layer IV; labeled cells were found mostly in layers III and V, with a relatively high density in layer V.
Neural associations of the substantia innominata in the rat: Afferent connections
Authors: Grove Elizabeth A. 
Published: January 2005

AbstractThe afferent connections of the substantia innominata (SI) in the rat were determined employing the anterograde axonal transport of Phaseolus vulgaris leucoagglutinin (PHA‐L) and the retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP), in combination with histochemical procedures to characterize the neuropil of the SI and identify cholinergic cells. Both neurochemical and connectional data establish that the SI is organized into a dorsal and a ventral division. Each of these divisions is strongly affiliated with a different region of the amygdala, and, together with its amygdalar affiliate, forms part of one of two largely distinct constellations of interconnected forebrain and brainstem cell groups.The dorsal SI receives selective innervation from the lateral part of the bed nucleus of the stria terminalis, the central and basolateral nuclei of the amygdala, the fundus of the striatum, distinctive perifornical and caudolateral zones of the lateral hypothalamus, and caudal brainstem structures including the dorsal raphe nucleus, parabrachial nucleus, and nucleus of the solitary tract. Projections preferentially directed to the ventral SI arise from the medial part of the bed nucleus of the stria terminalis, the rostral two‐thirds of the medial nucleus of the amygdala, a large region of the rat amygdala that lies ventral to the central nucleus, the medial preoptic area, anterior hypothalamus, medialmost lateral hypothalamus, and the ventromedial hypothalamus. Both SI divisions appear to receive afferents from the dorsomedial and posterior hypothalamus, supramammillary region, ventral tegmental area, and the peripeduncular area of the midbrain. Projections to the SI whose selectivity was not determined originate from medial prefrontal, insular, perirhinal, and entorhinal cortex and from midline thalamic nuclei. Findings from both PHA‐L and WGA‐HRP experiments additionally indicate that cell groups preferentially innervating a single SI division maintain numerous projections to one another, thus forming a tightly linked assembly of structures.In the rat, cholinergic neurons that are scattered throughout the SI and in parts of the globus pallidus make up a cell population equivalent to the primate basal nucleus of Meynert (Mesulam et al.: Neuroscience 10:1185–1201, '83). PHA‐L‐filled axons, labelled from lectin deposits in the dorsal raphe nucleus, peripeduncular area, ventral tegmental area, or caudomedial hypothalamus were occasionally seen to approach individual cholinergic neurons in the SI, and to contact the surface of such cells with axonal varicosities (putative synaptic boutons). Pending confirmation in an electron microscopic study, such findings suggest that several sources of innervation of the SI may provide afferents to the cholinergic cells in the region.
The ventral lateral geniculate nucleus in the cat: Thalamic and commissural connections revealed by the use of WGA‐HRP transport
Authors: Nakamura Hiroyuki , Kawamura Syosuke 
Published: January 2005

AbstractThe present investigation was carried out to clarify the topographical details of both the origin and terminal site of the thalamic projections and the commissural connections of the ventral lateral geniculate nucleus (LGNv) in the cat by using bidirectional transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP).Thalamic projections: Unilateral injections of WGA‐HRP into the LGNv produced orthograde labeling in the intralaminar nuclei bilaterally and in the lateralis posterior (LP) and the pulvinar (Pul) nucleus ipsilaterally. In the intralaminar nuclei the rostral part of the nucleus centralis lateralis (CL) was most densely labeled by orthogradely transported material, particularly in its dorsal and lateral large‐celled portion. Other intralaminar nuclei—such as the nucleus paracentralis, centralis medialis, and centralis dorsalis—also were labeled bilaterally with ipsilateral predominance, but no labeling was detected in the caudal portion of the CL and the centromedian and parafascicular nuclei. In the Pul, labeling of terminal ramifications was found to be concentrated in a region just medial to th so‐called retinorecipient zone of the Pul as a slim band of labeling inclining dorsoventrally. In the LP, fine labeled fibers were located in the lateral portion of the LP.Commissural connections: Commissural fibers crossed in the dorsal part of the posterior commissure and reached the most caudal part of the contralateral LGNv. Labeling in the contralateral LGNv was concentrated in the dorsomedial part of the medial zone that extends medially to the middle portion of the cerebral peduncle. Origins of the commissural connections arose mostly from the medial zone that roughly corresponds to the commissural terminal zone and partly from aberrant cells dispersed among optic tract fibers.From these results, together with the previous studies, it is concluded that although the cat's LGNv has connections with diverse structures in the central nervous system, the origin and terminal site of the connections are partially segregated within the nucleus, which suggests that the LGNv may contain functional subsystems.
Projections of digit afferents to the cuneate nucleus in the raccoon before and after partial deafferentation
Authors: Rasmusson Douglas D. 
Published: January 2005

AbstractWithin the cuneate nucleus of the raccoon, the representations of individual forepaw digits are anatomically separated by densely myelinated laminae. This unique arrangement was utilized to determine whether the terminations of cutaneous afferents from individual digits are precisely restricted to the appropriate region of the cuneate nucleus or overlap with afferents from adjacent digits. By using the transganglionic transport of horseradish peroxidase (HRP), it was found that, for each digit, the terminal labeling was restricted to the appropriate 150–250‐μm‐wide column that extended rostrocaudally throughout the nucleus. The topographical arrangement of digit input corresponded to the known electrophysiology, with the terminal column for the fifth digit located most medially within the nucleus and those for digits 4 to 1 successively more laterally. Within a column, the density of labeling was greater over cell clusters than between clusters. These results indicate that afferents from adjacent digits do not overlap in the cuneate nucleus. In six animals, the fifth digit was amputated, and 2–4 months later, HRP was injected into the nerves of the fourth digit to determine whether its afferents had sprouted into the denervated fifth‐digit column. The projection pattern from the fourth digit in each of these animals was the same as in normal animals and the same as in the intact contralateral side. These results indicate that the reorganization seen in the cerebral cortex following peripheral deafferentation cannot be attributed to changes in the afferent fiber projections to the cuneate nucleus.
Laminar distribution and morphology of gamma‐aminobutyric acid (GABA)‐immunoreactive neurons in the medial and dorsomedial areas of the cerebral cortex of the lizard Podarcis hispanica
Authors: Schwerdtfeger Walter K. , Lorente Maria‐José 
Published: January 2005

AbstractThe morphology and laminar distribution of immunolabeled neurons in the medial and dorsomedial telencephalic cortices of the lizard Podarcis hispanica were examined in vibratome sections after preembedding γ‐aminobutyric acid (GABA)‐immunocytochemistry. In both cortical areas and at all rostrocaudal levels, GABA‐immunoreactive neurons were found in all cortical layers, with the largest number (74%) of GABA‐positive cells in layer 3. GABA‐positive neurons were classified into pyramidlike, vertical‐fusiform, multipolar, and horizontal neurons. Cells that could be so classified were counted in each cortical lamina.In the medial cortex, multipolar and horizontal‐bipolar cells dominated layer 1. Layer 2 displayed mainly horizontal and pyramidlike cells at its outer margin and pyramidlike cells at its inner margin. In layer 3, horizontal cells were the prevalent group. In the dorsomedial cortex, layer 1 mainly contained small multipolar neurons (35% of layer‐1 cells) in its outer third and vertical‐fusiform neurons (37% of layer‐1 cells) in its inner two thirds. In layer 2, 47% of the few GABA‐positive perikarya were pyramidlike. The largest population of neurons in layer 3 was that formed by multipolar cells (45% of layer‐3 cells).Ultrastructural examination revealed that GABA‐immunoreactive neurons possessed indented euchromatic nuclei with a central nucleolus. Their cytoplasm contained numerous mitochondria and a very well‐developed granular endoplasmic reticulum. Their somata were contacted by numerous unstained boutons making asymmetric contacts and by a few symmetric synapses of GABA‐positive terminals. Dendrites of GABA‐immunoreactive cells were thin, with irregular outlines, and generally aspinous. Like the somata, dendrites were contacted by many unstained asymmetric synapses. Some dendritic profiles also received symmetric contacts from GABA‐positive boutons.GABA‐positive terminal‐like puncta were found throughout the layers, with a maximal concentration in layer 2. Electron microscopy confirmed that nearly all of the puncta represent GABA‐positive terminal boutons.Comparison of GABA‐immunoreactive cells in Podarcis with those found in the mammalian hippocampus suggests that these cells may be inhibitory neurons, as in the hippocampus of mammals.
Intrinsic connections of rat primary visual cortex: Laminar organization of axonal projections
Authors: Burkhalter Andreas 
Published: January 2005

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 organization of visual cortex.
Developmental plasticity of the rubrospinal tract in the North American opossum
Authors: Xu Xiao Ming , Martin George F. 
Published: January 2005

AbstractWe have shown previously that rubral axons can grow caudal to a lesion of their pathway at thoracic levels of the spinal cord in the developing opossum, Didelphis virginiana. In the present report we expand on that observation and present evidence which suggests that the critical period for plasticity of the rubrospinal tract ends earlier at cervical than at thoracic levels. In addition, we show that most rubrospinal neurons die as a result of axotomy during early stages of the critical period. The opossum was chosen for study because the development of its rubrospinal tract occurs after birth.In one set of experiments the area containing the rubrospinal tract was lesioned at cervical or thoracic levels and after 30 days or more, retrograde transport techniques were used to determine if rubral axons had grown caudal to the lesion. When the lesions were made at rostral cervical levels between estimated postnatal day 26 and maturity, neurons could not be labeled in the contralateral red nucleus by injections of retrograde markers ipsilateral to the lesion and caudal to it. We were not able to obtain adequate survival after cervical lesions made prior to estimated postnatal day 26. When the lesions were made at mid to caudal thoracic levels between estimated postnatal days 19 and 26, neurons could be labeled in the contralateral red nucleus. When comparable lesions were made at estimated postnatal day 40, there was usually a decrease in the number of labeled neurons, and when they were made at estimated postnatal day 54, none was labeled. In selected cases, operated at estimated postnatal day 19, cell counts provided evidence for loss of neurons in the red nucleus contralateral to the lesion.In orthograde transport experiments performed on animals with thoracic lesions of the rubrospinal tract made between estimated postnatal days 18 and 33, rubral axons could be labeled caudal to the lesion, and they seemed to take the most direct route around it. Although they sometimes assumed abnormal positions caudal to the lesion, rubral axons appeared to reach areas of the gray matter appropriate to them. When lesions were made at estimated postnatal day 54 or in older animals, labeled axons could be traced to the lesion site but not caudal to it.In still other experiments rubrospinal neurons were labeled by caudal thoracic or rostral lumbar injections of Fast Blue at estimated postnatal day 26 and 3–4 days later the injected animals were subjected to a lesion of the rubrospinal tract three segments rostral to the injection and ipsilateral to it. They were killed 30–34 days after the lesion so that the red nucleus contralateral to it could be examined for labeled neurons. The results showed that only a few rubrospinal neurons survived axotomy, suggesting that the growth of new axons around the lesion is a major factor in plasticity.
Evidence for an alteration of the tonotopic map in the gerbil cochlea during development
Authors: Sanes Dan H. , Merickel Michael , Rubel Edwin W 
Published: January 2005

AbstractWe have investigated developmental alterations in the tonotopic projection of the gerbil lateral superior olive. Single neurons were characterized in the frequency domain and the recording site marked with fast green. Transverse tissue sections from the auditory brainstem of each animal were visualized with a video‐equipped microscope, and the image was digitized for subsequent alignment. The three‐dimensional display indicated little variation in the rostrocaudal axis, allowing us to collapse the data into a two‐dimensional tonotopic map. The tonotopic map was found to change with age such that the characterstic frequency of neurons in a given anatomical location became successively higher during development. These results are consistent with the hypothesis that the place code gradually shifts in the developing cochlea.
Target dependence of hypoglossal motor neurons during development and in maturity
Authors: Snider W. D. , Thanedar S. 
Published: January 2005

AbstractWe have investigated the target dependence of hypoglossal motor neurons in postnatal rats by transecting the hypoglossal nerve and preventing reinnervation of the tongue. After transection in early postnatal life, approximately 60% of hypoglossal motor neurons die and surviving neurons are markedly atrophic compared to contralateral controls. In maturity, there is also substantial neuronal atrophy and about 30% of motor neurons appear to die after the procedure. However, most hypoglossal neurons in adults survive transection for periods up to 1 year. The adult response is present by 3 weeks of age.The time course of neuronal atrophy and death after permanent target deprivation was investigated in adult animals. One month after the hypoglossal nerve was deflected, there was marked axonal atrophy, although somatic atrophy was minimal. By 3 months after the procedure substantial neuronal atrophy and apparent cell loss (about 30%) had occurred. There was little change between 3 and 6 months.We conclude that hypoglossal motor neurons are influenced by connections with their targets in postnatal life. Even in maturity, neurons require target connections for maintenance of axonal and somatic morphology. However, the majority of motor neurons in adult animals can survive target deprivation for prolonged periods.