bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organization of eighth nerve afferent projections from individual endorgans of the inner ear in the teleost, Astronotus ocellatus
Authors: Meredith Gloria E. , Butler Ann B. 
Published: May 2005

AbstractEighth nerve fibers from the saccule, utricle, lagena, and the anterior, horizontal, and posterior semicircular canals of a cichlid fish were traced to the octavolateralis region of the brainstem using HRP and degeneration methods. The anterior, magnocellular, descending, and posterior nuclei of the octavus column receive inputs from all endorgans, whereas the tangential nucleus receives projections only from the utricle and semicircular canals. The most rostral projection from each endorgan is found in the eminen‐tia granularis of the vestibulolateral lobe of the cerebellum. Sparse terminals are found in the medial reticular formation from the utricle and semicircular canals, and utricular and saccular rami terminate in the vicinity of the lateral dendrite of the Mauthner cell.Utricular and semicircular canal projections consistently overlap centrally as do saccular and lagenar inputs. Afferent fibers from all endorgans end within relatively distinct regions throughout the octavus column of nuclei. Saccular and lagenar inputs lie dorsal to the semicircular canal terminations. Utricular endings are complex, however, in that they overlap dorsally with saccular and lagenar terminals and ventrally with the semicircular canal inputs. Cerebellar inputs are found only in the eminentia granularis of the vestibulolateral lobe, and the densest terminals are from the utricle and the Semicircuhr canals; the sparsest are from the saccule.Previous studies in fish have indicated that generally the utricle and semicircular canals are concerned with the maintenance of static and dynamic equilibrium whereas the saccule and lagena are concerned with auditory reception. There is recent evidence, however, for multiple functions within individual endorgans. Our anatomical findings suggest that in Astronotus each otolithic endorgan carries more than one modality; that the semicircular canals are concerned solely with an equilibrium function; and that acoustic information is processed dorsally and vestibular information ventrally along the octavus column of nuclei. No single nucleus appears to be solely auditory in function and only the tangential nucleus, situated ventrally in the octavus column, appears to be solely vestibular.
Fine structure and organization of the infrared receptor relays: Lateral descending nucleus of V in Boidae and nucleus reticularis caloris in the rattlesnake
Authors: Meszler Richard M. 
Published: May 2005

AbstractThe morphology of the lateral descending nucleus of V (LTTD) in three species of Boidae and nucleus reticularis caloris (RC) of the rattlesnake have been studied with the light and electron microscope. First‐ and second‐order relays in the infrared receptor pathway to the tectum are contained within LTTD in the Boidae, whereas in the rattlesnakes the secondary relay to tec‐tipetal neurons is in nucleus RC. The lateral descending nucleus in the boids contains small and large neurons. The larger cells project to the optic tectum and morphologically are quite similar to those of nucleus RC.It has been determined at the ultrastructural level that LTTD of the three species of boids studied have very similar morphology and organization. A marginal neuropil, located near the lateral descending tract, consists of terminals of thin unmyelinated axons in synaptic contact with thin den‐drites. Deeper within the nucleus primary afferent terminals containing clear spherical vesicles form synaptic clusters with dendrites and are post‐synaptic to other axon terminals containing pleomorphic vesicles. The large, tectipetal neurons are postsynaptic to two morphological types of synapses, one with clear spherical vesicles, asymmetric membranes, and subsynaptic web and the other with flattened vesicles and symmetrical membranes. Similar synapses are also present on the cells of nucleus RC in the rattlesnake.There is a close similarity in function, structure, and synaptic organization between the LTTD of boids and the LTTD plus nucleus RC of pit vipers, suggesting similar or identical evolutionary origin.
Columnar organization of corticocortical projections in squirrel and rhesus monkeys: Similarity of column width in species differing in cortical volume
Authors: Bugbee Nellie M. , Goldman‐Rakic Patricia S. 
Published: May 2005

AbstractTo compare the size and pattern of the terminal distribution of cortico‐cortical projections in two primate species with brains of different size, triti‐ated amino acids were injected into the prefrontal cortex of New World squirrel monkeys (Saimiri sciureus) and Old World rhesus monkeys (Macaca mulatta), and their brains were processed for light microscopic autoradiog‐raphy. In both species, prefrontal efferents are directed to a number of cortical targets in the same and opposite hemispheres, where in coronal sections, they generally terminate as radially oriented columns. In the rhesus monkey, the median width of the columns in transverse sections is 685 μ. In squirrel monkey, corresponding columns have a median width of 555 μ. Considering that the volume of the neocortex in rhesus monkey is approximately 4.5 × larger than that of squirrel monkey, the dimensions of cortical columns in the two species are surprisingly similar. This finding suggests that phylogenetic expansion in cortical surface area is accompanied by an increase in the number, rather than the width, of afferent fiber columns. The increase in number of modular units may be relevant to the increasing computational and information processing capacity of the cerebral cortex in the course of evolution.
Structural basis of orientation sensitivity of cat retinal ganglion cells
Authors: Leventhal Audie G. , Schall Jeffrey D. 
Published: May 2005

AbstractWe investigated the structural basis of the physiological orientation sensitivity of retinal ganglion cells (Levick and Thibos, '82). The dendritic fields of 840 retinal ganglion cells labeled by injections of horseradish peroxidase into the dorsal lateral geniculate nucleus (LGNd) or optic tracts of normal cats, Siamese cats, and cat deprived of patterned visual experience from birth by monocular lid‐suture (MD) were studied. Mathematical techniques designed to analyze direction were used to find the dendritic field orientation of each cell. Statistical techniques designed for angular data were used to determine the relationship between dendritic field orientation and angular position on the retina (polar angle). Our results indicate that 88% of retinal ganglion cells have oriented dendritic fields and that dendritic field orientation is related systematically to retinal position. In all regions of retina more than 0.5 mm from the area centralis the dendritic fields of retinal ganglion cells are oriented radially, i.e., like the spokes of a wheel having the area centralis at its hub. This relationship was present in all animals and cell types studied and was strongest for cells located close to the horizontal meridian (visual streak) of the retina. Retinal ganglion cells appear to be sensitive to stimulus orientation because they have oriented dendritic fields.
Neuronal composition and development in lamina 4C of monkey striate cortex
Authors: Mates Sharon L. , Lund Jennifer S. 
Published: May 2005

AbstractLamina 4C (Lund, '73) of the monkey, Macaca nemestrina, visual striate cortex occupies a key position as a principal recipient zone of axons from the lateral geniculate nucleus (LGN). Synaptic maturation in lamina 4C is of particular interest since it involves a competitive interaction between thalamic axons for postsynaptic territory: an interaction which is strongly influenced by afferent activity (Hubel et al., '77). As an initial step toward understanding the normal process of synapse maturation in 4C, this study examines Golgi material to define the adult neuron populations of subdivisions 4Cα (receiving afferents from magnocellular LGN) and 4Cβ (receiving afferents from parvocellular LGN). Three groups of spine‐bearing neurons are described‐one relatively confined to either α or β subdivision, the other two bridging the depth of 4C; four groups of smooth dendritic neurons interact with the spine‐bearing population. Electron microscopy of normal and Golgi‐impregnated tissue is used to define key features of synapse populations on these neurons. From embryonic day 159 through adulthood the smooth and spiny neurons occur in the same constant proportions in the neuropil (5% smooth, 95 % spiny). Changes in the distribution of synapses on the spiny neurons are analyzed qualitatively; type 1 axon terminals (asymmetric apposition ‐round vesicles) shift from dendritic shafts to spine tips during maturation. Each spine is found to bear a type 1 contact at all ages; these results allow us to conclude that the figures of Boothe et al. ('79) on changes in spine populations during maturation can now be interpreted as changes in type 1 synapse populations. It is shown that type 2 synapses (symmetric appositions ‐pieomorphic vesicles) arise from axons of the smooth dendritic neurons. These synapses are found to increase in number on the spiny cell somata in early postnatal development, and this is followed by a decrease in number to the adult level.
Spine formation and maturation of type 1 synapses on spiny stellate neurons in primate visual cortex
Authors: Mates Sharon L. , Lund Jennifer S. 
Published: May 2005

AbstractThis study continues an investigation (Mates and Lund, '83a) of neuronal development in lamina 4C of macaque monkey striate visual cortex. The maturational history of the type 1 synaptic contacts on spine‐bearing stellate neurons, which comprise 95% of the neurons of the lamina, is described. It is shown that type 1 contacts are initially found on the dendritic shafts; these contacts appear to be carried out on spine outgrowths. This leads to the adult condition where type 1 contacts are found only on the spine tips. A similar phenomenon has been reported for pyramidal neurons of the rat (reported during the course of this study by Miller and Peters, '81). In later maturation the spine and its type 1 contact may be lost; profiles found in the neuropil illustrate a process of shrinkage and detachment of both the type 1 axon terminals and postsynaptic dendritic spines in normal maturation. These findings provide an explanation for the marked increase and decrease in spine populations observed to occur on these neurons during normal maturation in an earlier study by Boothe et al. ('79).
The nucleus praeeminentialis: A Golgi study of a feedback center in the electrosensory system of gymnotid fish
Authors: Sas Emilia , Maler Leonard 
Published: May 2005

AbstractThe cytoarchitecture of the dorsal nucleus praeeminentialis in two families of weakly electric fish (Eigenmannia viriscens and Apteronotus albifrons) was examined in both Nissl and Golgi material, and an attempt was made to correlate this information with our data from HRP studies on the afferent and efferent connections of this nucleus.The n. praeeminentialis is an isthmic structure located dorsolateral to the lateral lemniscus and anterior to the eminentia granularis‐a subdivision of the archicerebellum of fish. The n. praeeminentialis can be divided into a large dorsal portion concerned with electroreception and a small ventral portion involved with the lateral line mechanoreception. The dorsal n. praeeminentialis consists of three parts: a pars medialis, a large pars principals (p.P.) and a narrow pars lateralis. The p.P. presents three zones: a dorsal, a central, and a ventral zone, which are reciprocally and topographically connected with the zones of the electroreceptive lateral line lobe (ELLL), medial ELLL with ventral zone, central ELLL with central zone, and lateral ELLL with dorsal zone. Several types of projection cells are present in the n. praeeminentialis: (a) neurons that show preferential orientation of their long dendrites in relation to the afferent fiber systems, (b) cells with wide dendritic fields radiating in all directions, and (c) cells with small polarized dendritic fields toward the incoming ELLL afferents.Interneurons are also identified, showing different axonal ramification patterns.The afferent and efferent fiber systems linking the n. praeeminentialis to ELLL, lobus caudalis (L.C.), and torus semicircularis (T.S.d.) point to the important position of this nucleus in the feedback loop of the electrosensory pathway. The complex processing within this nucleus is reminiscent of the feedback loops in the auditory system.
Central projections of the octavolateralis nerves of the clearnose skate, Raja eglanteria
Authors: Koester David M. 
Published: May 2005

AbstractThe central projections of first‐order lateral line and octavus nerve afferents of the clearnose skate, Raja eglanteria, were, determined by nerve degeneration and horseradish peroxidase techniques. The octavolateralis area of the medulla, which receives these afferents, is organized into dorsal, intermediate, and ventral longitudinal columns of cells and neuropil. Fibers that innervate the electroreceptive sense organs enter the dorsal longitudinal column via the dorsal root of the anterior lateral line nerve and terminate within the dorsal nucleus. Mechanoreceptive fibers from neuromasts of the head and trunk are carried by the ventral root of the anterior lateral line nerve and posterior lateral line nerve, respectively. Both nerves enter the intermediate longitudinal column and terminate throughout the rostrocaudal extent of the intermediate nucleus. Fibers of the ventral root of the anterior lateral line nerve are confined to the medial portion of the intermediate nucleus and posterior lateral line nerve fibers to the lateral portion. In addition, ascending mechanoreceptive fibers from both head and trunk neuromasts project to the vestibulolateral lobe of the cerebellum.Octavus nerve afferents enter the medulla and terminate primarily within the four octaval nuclei that comprise the ventral longitudinal column. Rostrocaudally, these nuclei are the anterior, magnocellular, descending, and posterior octaval nuclei. A few ascending axons continue beyond the anterior octaval nucleus and course to the vestibulolateral lobe of the cerebellum. Some descending axons emanate from the descending octaval nucleus and course to the reticular formation and intermediate nucleus.Therefore, electroreceptive lateral line, mechanoreceptive lateral line, and octavus nerve afferents project ipsilaterally and terminate predominantly within separate medullary nuclei. The significance of octavus nerve projections to the intermediate nucleus and overlap of mechanoreceptive and octavus afferents within the vestibulolateral lobe of the cerebellum cannot be determined until it is known which fibers of the inner ear sense organs project to these areas.Retrograde transport of horseradish peroxidase results in the labeling of large multipolar cells, both ipsilaterally and contralaterally, within a column of gray that lies dorsolateral to the reticular formation. These cells are interpreted as the cells of origin of the efferent components of the anterior and posterior lateral line nerves.
The properties of neurones recorded in the superficial dorsal horn of the rat spinal cord
Authors: Woolf Clifford J. , Fitzgerald Maria 
Published: May 2005

AbstractThe physiological properties of neurones in the superficial laminae of the dorsal horn of the fourth and fifth lumbar segments of the rat spinal cord have been investigated in decerebrate spinal animals. Both extracellular recordings with platinum‐plated tungsten microelectrodes (n = 72) and intracellular recordings with glass microelectrodes (N = 79) were made. Attempts were made to fill cells intracellularly with horseradish peroxidase or Lucifer Yellow. Thirty‐seven percent of the intracellularly injected neurones were recovered after histological processing and their cell bodies found to be in lamina 1 or 2 and in the dorsal white matter overlying lamina 1. The dendritic spread of the stained neurones was maximal in the rostrocaudal plane with a restricted mediolateral spread. The physiological properties of the extracellularly recorded units, the intracellularly unidentified units, and the intracellularly stained units were the same. The neurones were characterized by low background activity and all had excitatory receptive fields on the lower limb. Some neurones responded only to low‐threshold mechanical stimulation of the skin or only to noxious skin stimulation but the majority of units (58%) were wide‐dynamic‐range cells responding to both types of stimuli. Receptive field classification was made questionable, however, by the existence of cells (9%) that exhibited a spontaneous shift in the size of their receptive fields and in the type of stimulus that elicited a response. The neurones in the superficial dorsal horn commonly showed a marked inhibition to repeated cutaneous stimuli (27%) or a prolonged afterdischarge followed a single stimulus (20%). Afferent input from the sural nerve was found to be from A and C fibres in both extra‐ and intracellular recordings. Aδ‐ and C‐mediated excitations were most common although convergent inputs from Ab̃‐fibres occurred in 40% of units.No correlation was found between cell structure or distribution of dendritic fields and physiological properties in our small sample of intracellularly stained cells. The morphology of the cells was highly diverse, as were the different receptive fields. There was, however, some correlation between the location of cell bodies and their responses. Neurones responding only to low‐threshold stimuli were distributed either in the dorsal white matter or in inner lamina 2. Wide‐dynamic‐range cells were distributed throughout the superficial dorsal horn. These results suggest that neurones of different shapes and positions may subserve the same function and, conversely, that neurones of the same shape and position may subserve different functions.
The distributions of photoreceptors and ganglion cells in the California ground squirrel, Spermophilus beecheyi
Authors: Long Kenneth O. , Fisher Steven K. 
Published: May 2005

AbstractThe topographical distributions of photoreceptors and ganglion cells of the California ground squirrel (Spermophilus beecheyi) were quantified in a light microscopic study. The central retina contains broad, horizontal streaks of high photoreceptor density (40–44,000/mm2) and high ganglion cell density (20–24,000/mm2). The isodensity contours of both cell types are elliptical and oriented along the nasal‐temporal axis. There are roughtly fivefold decreases in both photoreceptor and ganglion cell densities with increasing eccentricity, the lowest densities being found in the superior retina. Large transitions in cell density and retinal thickness occur across the linear optic nerve head. Rod frequency increases with increasing eccentricity, from 5 to 7% in the central retina to 15 to 20% in the periphery. Roughly 10% of the cones possess wide, dark‐staining ellipsoids. These cones are uniformly distributed across the retina which suggests that they may belong to a separate cone class, possibly blue‐sensitive cones. The ganglion cell soma size distribution is unimodal, with the majority of somata being 25–50 μm2. Large ganglion cells (somata > 100 μm2) are rare in the central retina, but their frequency increases with increasing eccentricity. No evidence for separate size classes of ganglion cells was found. The gradual decrement of photoreceptor density across the ground squirrel retina suggests that there are only relatively small changes in acuity across much of the animal's visual space compared with species possessing either a narrow visual streak or fovea or area centralis.
A comparison of the normal and regenerated retinotectal pathways of goldfish
Authors: Stuermer Claudia A. O. , Easter Stephen S. 
Published: May 2005

AbstractThis is a light and electron microscopic study of the retinotectal pathway: intact and after regeneration of the optic nerve. The spatiotemporal pattern of axonal outgrowth and termination was studied with the methods of proline autoradiography, horseradish peroxidase (HRP) labeling, and fiber degeneration.The spatial order of optic fibers in the normal and regenerated pathways was assessed by labeling small groups intraretinally with HRP and then tracing them to the tectum. The labeled fibers occupied a greater fraction of the cross section of the regenerated than the normal optic tract. At the brachial bifurcation, roughly 20% of the regenerated fibers chose the incorrect brachium vs. less than 1% of the normals. In tectum, the regenerated optic fibers reestablished fascicles in stratum opticum, but they were less orderly than in the normals. The retinal origins of the fibers in the fascicles were established by labeling individual fascicles with HRP and then, following retrograde transport, finding labeled ganglion cells in whole‐mounted retinas. Labeled cells were more widely scattered over the previously axotomized retinas than over the normal ones. A similar result was obtained when HRP was applied in the tectal synaptic layer. All of these results indicate that the pathway of the regenerated optic fibers is less well ordered than the intact pathway.Both autoradiography and HRP showed that the regenerating optic fibers invaded the tectum from the rostral end, and advanced from rostral to caudal and from peripheral to central tectum, along a front roughly perpendicular to the tectal fascicles. Synapses of retinal origin were noted electron microscopically in the tectum at the same sites where autoradiography indicated that the fibers had arrived. No retinal terminals were seen where grain densities were at background levels. Fiber ingrowth and synaptogenesis apparently occurred simultaneously. The synapses were initially smaller and sparser than in normals, but were in the normal tectal strata and contacted the same classes of post synaptic elements as in normals.
Morphometry of intracellularly labeled neurons of the auditory nerve: Correlations with functional properties
Authors: Liberman M. Charles , Oliver Mary E. 
Published: May 2005

AbstractSingle auditory‐nerve fibers were injected with horseradish peroxidase after their tuning properties, characteristic frequencies, and spontaneous discharge rates were measured. From these functional properties virtually all other aspects of auditory‐nerve response can be predicted. Labeled fibers were reconstructed from the point of peripheral termination on cochlear hair cells to the point at which they enter the cochlear nucleus. Several morphological properties were measured at the light‐microscopic level, including axonal diameter, axonal length, internodal distances, cell‐body area, and cell‐body shape. All of these parameters were correlated, though some weakly, with characteristic frequency. However, only axonal diameter was correlated with spontaneous discharge rate.