bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neck muscle afferent projections to the brainstem of the monkey: Implications for the neural control of gaze
Authors: Edney Daniel P. , Porter John D. 
Published: January 2005

AbstractBrainstem projections of first‐order afferent neurons that innervate the suboccipital muscles of the monkey have been determined by using the technique of transganglionic transport of wheat‐germ‐agglutinin‐conjugated horseradish peroxidase (WGA/HRP) and HRP. Neck muscle afferents distribute to several distinct regions located within the caudal brainstem and rostral spinal cord. Terminal labeling was heaviest within the ventral portion of the ipsilateral lateral cuneate nucleus. Muscle afferent terminals also distributed to ventrolateral portions of the pars triangularis division of the cuneate nucleus. Projections were consistent with the known somatotopic (i.e., both place and modality) organization of the cuneate nucleus. Moreover, neck muscle projections to the cuneate nucleus were, in part, coincident with those previously demonstrated for the extraocular muscles (Porter: J. Comp. Neurol. 247:133–143, '86). Sparse terminal projections were noted in the central cervical nucleus. In addition, light terminal labeling was present in group x of the vestibular complex and in an ill‐defined region along the lateral margin of the brainstem.Present observations, which provide the first complete description of the central distribution of neck muscle afferent neurons in the primate, may contribute to the known substrate for eye/head coordination.
Differential origin of brainstem serotoninergic projections to the midbrain periaqueductal gray and superior colliculus of the rat
Authors: Beitz A. J. , Clements J. R. , Mullett M. A. , Ecklund L. J. 
Published: January 2005

AbstractPrevious studies have shown that both the midbrain periaqueductal gray (PAG) and the superior colliculus receive a significant serotoninergic (5‐HT) innervation. In the present study the origins of these 5‐HT projections to the rodent PAG and superior colliculus were analyzed by using a combined immunohistochemical‐retrograde transport technique. Thirteen brainstem regions were found to contain double‐labelled 5‐HT‐like immunoreactive neurons following HRP injections into the PAG while only four brainstem nuclei contained double‐labelled neurons following superior collicular injections. After HRP deposits into the ventral PAG, the largest percentage of double‐labelled neurons was identified in nucleus raphe magnus, pars alpha of the nucleus gigantocellularis, and the paragigantocellular nucleus. The dorsal PAG, on the other hand, received the largest percentage of its 5‐HT projections from nuclei raphe dorsalis, raphe obscurus, raphe pontis, and raphe medianis. The 5‐HT input to the superior colliculus was found to arise exclusively from nuclei raphe dorsalis, raphe medianis, and raphe pontis and from the contralateral periaqueductal gray. Raphe nuclei were found to contribute serotoninergic projections to both the PAG and the superior colliculus while reticular nuclei contributed 5‐HT projections only to the PAG. Injections of the fluorescent retrograde tracers true blue and nuclear yellow were then made into the PAG and superior colliculus to ascertain if neurons located in raphe nuclei that projected to both structures provided axon collaterals to both areas. Generally, less than 10% of raphe neurons projecting to the superior collicuius were identified as providing axon collaterals to the PAG.The present results demonstrate major quantitative and qualitative differences in the origin of 5‐HT projections to the ventral PAG and superior colliculus. The origin of 5‐HT input to the dorsal PAG, on the other hand, showed many similarities to the origin of 5‐HT innervation of the superior colliculus. These data also indicate that approximately 35% of raphe neurons provide nonserotoninergic projections to the PAG and superior colliculus.
Times of generation of glutamic acid decarboxylase immunoreactive neurons in mouse somatosensory cortex
Authors: Fairén Alfonso , Cobas Alberto , Fonseca Montserrat 
Published: January 2005

AbstractThe birth dates of neurons showing glutamic acid decarboxylase (GAD) immunoreactivity have been determined in mouse somatosensory cortex. Pregnant C57B1 mice received pulse injections of (3H)thymidine from E10 through E17 (EO being the day of mating). The distributions of thymidinelabeled, GAD‐positive and nonimmunoreactive (non‐GAD) cells as a function of depth under the pial surface were recorded in adult animals. The maximum rate of generation of GAD‐positive neurons occurred at E14, whereas the generation of non‐GAD neurons reached its maximum rate at E13. Except for those in layer I, GAD‐positive neurons followed an inside‐out sequence of positioning. GAD‐positive neurons born at E12 and E13 were located in layers VI—IV. GAD‐positive neurons born at E14 were found throughout the cortical thickness, with a maximum in layer IV. The GAD‐positive neurons labeled after pulses at E15 or E16 or E17 were limited to the superficial strata, forming a band that became narrower as it moved toward the pial surface with increase in age of pulse labeling. GAD‐positive neurons in layer I were generated at a constant rate during the whole embryonic period analyzed. Non‐GAD neurons also followed an inside‐out spatiotemporal gradient. Two partially overlapping phases were distinguished in non‐GAD neurogenesis. During the first phase (from E12 to E14) neurons populating adult layers VI and V originated, while neurons located in layers IV through I were generated during the second phase (from E13 to E17). Since GAD‐immunoreactive neurons form a heterogeneous population, we envisage further studies in order to test whether differences exist in birth dates among the classes.
Organization of the reciprocal connections between the subiculum and the enthorhinal cortex in the cat: II. An electrophysiological study
Authors: Van Groen T. , Da Silva F. H. Lopes 
Published: January 2005

AbstractThe projection of the entorhinal cortex (EC) to the subiculum (SUB) and the projection in the opposite direction from the SUB to the EC have studied in the cat by using electrophysiological methods. Field potentials elicited by EC stimulation were recorded in the SUB. Different topographic distributions of the amplitude of the average evoked potentials (AEPs) were obtained dependig on the place of stimulation along a lateromedial axis in the EC. Stimulation of the lateral EC elicited the largest AEPs in the septal part of the SUB whereas stimulation of the medical EC evoked maximal responses in the temporal part of the SUB. Field potentials evoked by subicular stimulation were measured in the EC; the topographic distribution of the AEPs was dependent on the place of stimulation along the subicular septotemporal axis. Septal SUB stimulation elicited the largest field potentials in the laterocaudal part of the EC whereas temporal SUB stimulation evoked maximal responses in the mediocaudal part of the EC. These findings indicate that a topographical organization exists in the EC‐SUB connections and that these connections are reciprocal. Unit activity both orthodromicaally and antidromically elicited by SUB stimulation was recorded in the EC. Mean conduction velocities were estimated and found to vary around 1 m/second−1. The physiological evidence is discussed along with the anatomical data reported in the accompanying paper.
Role of competitive interactions in the postnatal development of X and Y retinogeniculate axons
Authors: Garraghty P. E. , Sur M. , Sherman S. M. 
Published: January 2005

AbstractThe cat's retinogeniculate pathway is largely composed of X and Y axons, which represent two distinct neuronal streams organized in parallel. Our earlier data, summarized in the previous paper, suggest that the postnatal development of retinogeniculate axon arbors is characterized by competitive interactions between the X and Y axons. Thus, during development, X arbors in lamina A or A1 are initially broad or exuberant before the Y arbors begin to develop adultlike arbors; the X arbors then shrink to their adult form as the Y arbors grow and establish their mature complement of connections; monocular lid suture prevents the rapid growth of Y arbors, which in turn prevents the pruning of X arbors; and monocular enucleation at birth allows X arbors from the remaining eye to retain their exuberance although completely confined to their appropriate lamina A or A1, whereas the Y arbors develop aberrant extensions into adjacent, previously denervated laminae. We now provide additional evidence for the role of competition between retinogeniculate X and Y axons during development. The addition of visual deprivation by lid suture of the remaining eye to monocular enucleation at birth causes no apparent change in the morphology of X arbors in laminae A and A1. In contrast, the Y arbors of such cats continue to form extensive translaminar sprouts in the previously denervated laminae despite severely reduced terminations in the lamina A or A1 normally innervated by the remaining eye. We interpret these new data, in conjunction with our earlier data, as follows. If retinogeniculate X and Y arbors compete for synaptic space during postnatal development, terminations of Y axon can be affected by lid suture only in geniculate laminae where terminations of X axons are also present. Thus, Y axon arbors are severely reduced in deprived lamina A or A1 following lid suture whether or not the other eye is removed. Where X arbors are not present, such as in lamina C or the laminae inappropriate for the remaining eye after removal of the other, the lid suture has no obvious effect on development of the Y arbors.
Role of target tissue in regulating the development of retinal ganglion cells in the albino rat: Effects of kainate lesions in the superior colliculus
Authors: Carpenter Paul , Sefton Ann Jervie , Dreher Bogdan , Lim Wei‐Leng 
Published: January 2005

AbstractKainic acid or ibotenic acid was injected unilaterally into the major target regions of the axons of retinal ganglion cells—the superior colliculus (SC) or dorsal lateral geniculate nucleus (DLG)—of rat pups ranging in age from postnatal day 0 to postnatal day 10 (PO – P10). While the collicular or geniculate neurons within the injection site died within 48 hours of the injection, damage to axons and terminals of extrinsic origin within the injection region was not apparent. The neuronal degeneration induced by the neurotoxins, observed at both the light and electron microscopic levels, resembled the neuronal degeneration that occurs in the colliculus during normal development. Macrophages were identified in the regions containing degenerating cells.Two to three weeks after the injections of neurotoxin, massive injections of the enzyme, horseradish peroxidase (HRP), were made into the retinorecipient nuclei. After about 24‐hour survival time the numbers of retinal ganglion cells were estimated by counting the number of neurons containing HRP reaction products in sample areas distributed in a regular rectangular array across the entire retinal surface.In the animals in which the neurotoxin was injected into the SC during the first 4 postnatal days, there was a substantial reduction (on average 41.5%; the range: 27.5–65.5%) in the normal number (mean value of 113,000—Potts et al.: Dev. Brain Res. 3:481–486, '82) of retinal ganglion cells surviving the period of naturally occurring ganglion cell death in the retinae contralateral to the injected SC. By contrast, injections of neurotoxins into the DLG and/or the optic tract of newborn rats did not result in a significant reduction in the numbers of retinal ganglion cells surviving the period of naturally occurring ganglion cell death. The period of sensitivity of retinal ganglion cells to the injection of neurotoxin into the colliculi extends from birth to about the end of the first postnatal week; the greatest sensitivity seems to be restricted to the first 3–4 postnatal days.In the retinae in which the total number (and density) of ganglion cells was substantially reduced by the selective destruction of their target cells, the centroperipheral difference in the somal diameters of the ganglion cells (apparent in normal animals) was abolished, both amongst the whole population of ganglion cells and amongst the ganglion cells with the largest somata, relatively thick axons, and large‐gauge primary dendrites (Class I cells). The number and distribution of the Class I cells in the depleted retinae were, however, unaltered. The abolition of the centro‐peripheral difference in somal sizes results mainly from an increase in the somal size of the centrally located ganglion cells.
Afferent and efferent projections of the inferior area 6 in the macaque monkey
Authors: Matelli Massimo , Camarda Rosolino , Glickstein Mitchell , Rizzolatti Giacomo 
Published: January 2005

AbstractThe rostral part of the agranular frontal cortex (area 6) can be subdivided on the basis of its cytoarchitecture, enzymatic properties, and connections into two large sectors: a superior region, lying medial to the spur of the arcuate sulcus, and an inferior region, lying lateral to it. In this study we traced the afferent and efferent connections of the inferior region of area 6 by injecting small amounts of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) and fluorescent tracers (fast blue and diamidino yellow) into restricted parts of inferior area 6 and in physiologically determined fields of area 4.There is an ordered topographic pattern of connections between inferior area 6 and area 4. The region near the spur of the arcuate sulcus (hand field) projects to the area 4 hand field while the lateral part of inferior area 6 (mouth field) is connected with the corresponding field in area 4. The organization of the connections between the two fields is, however, different. The hand fields in area 6 and 4 have direct reciprocal projections, whereas the mouth field in the postarcuate cortex relays information to area 4 via a zone intermediate between the arcuate and the central sulcus. This zone corresponds to the cytochrome oxidase area F4 (Matelli, Luppino, and Rizzolatti:Behav. Brain Res. 18: 125–137, '85). The inferior area 6 also has topographically organized connections with the supplementary motor area.The inferior area 6 receives and sends fibers to a series of discrete cortical areas located in the lower cortical moiety (Sanides: The Structure and Function of the Nervous Tissue, Vol. 5. New York: Academic Press, pp 329–453, '72). These areas that form a broad ring around the central sulcus are the ventral bank of the principal sulcus and the adjacent area 46, the precentral operculum (PrOC), area SII (Jones and Burton: J. Comp. Neurol. 168:197–248, '76), the parietal operculum, and the rostral part of the inferior parietal lobule including the lower bank of the intraparietal suclus. Finall, the inferior area 6 has sparse but consistent connections with insular and cingulate cortices. The functional significance of this complex pattern of connections is discussed.
Immunoreactivity in Limulus. II. Studies of serotoninlike immunoreactivity, endogenous serotonin, and serotonin synthesis in the brain and lateral eye
Authors: Chamberlain Steven C. , Pepper John , Battelle Barbara‐Anne , Wyse Gordon A. , Lewandowski Thomas J. 
Published: January 2005

AbstractSerotoninlike immunoreactivity was examined by the fluorescein‐iso‐thiocyanate‐labeled secondary antibody technique in the lateral eye and brain of Limulus. Endogenous serotonin was measured with high‐perfor‐mance liquid chromatography and electrochemical detection. The synthesis of [3H]serotonin from [3H]tryptophan was measured in the presence and absence of reserpine. Fibers with serotoninlike immunoreactivity were found in the proximal stalks of the corpora pedunculata, in the neuropil of the central body, in the neuropils of the visual centers (lamina, medulla, and ocellar gnaglion), in the optic tract that connects the ocellar ganglion with the posterior medial medulla, and in the central neuropil of the brain. Immunoreactive somata were found in four groups in the brain. Up to 50 somata were scattered through each side of the dorsal medial group that lies centered on the dorsal surface within the curve of the centra body. These neurons innervate the central body neuropil and send processes into the central neuropil. Three of four reactive somata formed the ventral pole of each medullar group. These may provide the innervation of the proximal stalk of the corpora pedunculata. Five to ten reactive neurons were observed anteriorly in the ventral posterior lateral group #2 on each side that send processes into the central neuropil. Ten to 15 reactive somata were found on either side of the midline in the dorsal anterior part of the ventral medial group that contribute processes to the central neuropil. The remainder of the brain was not immunoreactive. No immunoreactive fibers or somata were found in the lateral eye or in the lateral optic nerve. Serotoninlike and substance P‐like immunoreactivities were not found to be colocalized anywhere in the brain. Significant amounts of endogenous serotonin were detected in the lamina and medulla whose neuropils are rich in immunoreactive fibers and in the central body and dorsal medial group that are also rich in immunoreactive somata and fibers. No endogenous serotonin was detected in either the lateral eye of the lateral optic nerve. The lamina, medulla, and central body and dorsal medial group also synthesized and stored [3H]serotonin from [3H]tryptophan. It is likely that serotonin is a neurotransmitter in the brain, but not in the lateral eye of the horseshoe crab. In particular, it appears that serotoninergic neurons may play a role in central visual processing.
Morphology of physiologically identified thalamocortical relay neurons in the rat ventrobasal thalamus
Authors: Harris Roger M. 
Published: January 2005

AbstractThe anatomical structure of physiologically identified neurons of the rat ventrobasal thalamus was studied in order to determine if there are morphologically distinct subsets of neurons that correlate with the somatosensory submodalities processed by these cells. Intracellular recordings were used to determine the modality and receptive field of a neuron, after which horseradish peroxidase was iontophoretically injected into the cell, allowing it to be histologically visualized. Computer‐assisted measurements of the labeled cells were made to quantitatively analyze the dendritic structure. Cells were divided into physiological groups stimulated by whiskers, glabrous skin, furry skin, noxious stimulation, or joint rotation. Qualitatively, all cells appeared similar, with the same types of branching patterns. Dendritic spines and long, sinuous appendages were found on all distal dendrites. Quantitatively, no statistically significant differences in dendritic structure were found between functionally defined groups with the aid of a number of parameters, including a fitted dendritic ellipse. There was a weak correlation between somal cross‐sectional area and receptive field size, suggesting larger cells processed larger receptive fields. In summary, the ventrobasal thalamus of the rat, in contrast to that of higher mammals, appears to contain only one major cell type and to have a very simple neuronal circuitry.
Retinal crowding alters the morphology of alpha ganglion cells
Authors: Kirby Michael A. , Chalupa Leo M. 
Published: January 2005

AbstractIt has been hypothesized that the dendritic field size of individual retinal ganglion cells is regulated early in development by interactions among neighboring cells (Wässle and Reiman, Proc. R. Soc. Lond. B. 200:441–461, 1978). An opportunity to test this hypothesis is provided by the consequences of prenatal enucleation that results in an increased density of ganglion cells in the remaining retina (Chalupa et al., Neuroscience 12:1139–1146, 1984). In the present study we compared dendritic field diameters of alpha ganglion cells in normal retinas to those of adult cats that were monocularly enucleated before birth (on embryonic days 42 and 51) and 6 days after birth. In each animal ganglion cells were labeled by central injections of horseradish peroxidase. The retinas were incubated according to a modified Hanker‐Yates procedure and whole‐mounted. All cells were sampled from the temporal retina along a corridor estalished by a line drawn through the optic disk and the area centralis. Alpha cells were differentiated into ON and OFF subtypes on the basis of their level of stratification in the inner plexiform layer (Peichl and Wässle, Proc. R. Soc. Lond. B. 212:139–156, 1981). Dendritic field and soma diameters were determined from complete cell drawings by calculating the mean of the two longest orthogonal diameters.Our main findings are: (1) Early monocular enucleation does not disrupt the mosaics of ON and OFF alpha ganglion cells in the remaining retina of adult animals. (2) Within the retinal corridor sampled, the density of alpha cells was substantially greater than normal in the remaining retina of the prenatal enucleates at all eccentricities except the far periphery. (3) Except at the far periphery, the dendritic field diameters of the prenatally enucleated animals were significantly smaller than normal when compared at equivalent eccentricities. However, when compared at equivalent cell densities, dendritic field dimensions in the prenatally enucleated and normal animals were found to be similar. (4) In the prenatal enucleates the somas of these neurons were also significantly smaller than normal. (5) If the monocular enucleation was postnatal, however, the density and the dendritic field diameters of alpha cells did not differ appreciably from normal.These results indicate that the morphology of retinal ganglion cells can be influenced by increasing the density of developing ganglion cells. The reduced size of dendritic fields and somas in the remaining retina of prenatally enucleated animals may reflect increased cellular interactions due to ganglion cell “crowding.” It is suggested that both intraretinal interactions and competition among axon terminals contribute to establishing the adult retinal ganglion cell organization.