bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relative numbers of several types of synaptic connections in the substantia gelatinosa of the cat spinal cord
Authors: Duncan Donald , Morales Ricardo 
Published: January 2005

AbstractThe relative numbers of axo‐dendritic, axo‐axonic, dendroaxonic and dendro‐dendritic synapses were determined by classifying and recording all such specialized contacts in sample areas of the substantia gelatinosa. The samples were taken from segments L1‐L5 of the cat spinal cord. In the glomerular complexes 97% of all synapses were recorded as axon‐dendritic. In substantia gelatinosa deprived of glomerular complexes by dorsal root section, 96.5% were axo‐dendritic. The remainders were about equally divided between axo‐amonic, dendro‐dendritic and dendro‐axonic synapses.
Nerve fibers of the eighth nerve and their distribution to sensory nerves of inner ear in the bullfrog
Authors: Dunn Robert F. 
Published: January 2005

AbstractThe number of both myelinated and unmyelinated nerve fibers has been determined of the eighth nerve and each of its sensory branches in the bullfrog. No significant differences were found in the size distribution of the myelinated nerve fibers among the three ampullary nerves or between the saccular and lagenar nerves. Comparison of these two functional groups also showed no significant differences in the myelinated nerve fiber size distribution between the angular acceleration and otolithic receptors, collectively the equilibrium receptors. The wide variability, that was found not only among the animals but also between the right and left sides, most likely resulted in the absence of differences. Highly significant differences were noted when the myelinated nerve fiber diameter distributions to the acoustic organs were compared to those of the equilibrium organs. The most notable difference was the absence of any myelinated nerve fibers whose diameters were greater than 8 μm.
Sources and terminations of callosal axons related to binaural and frequency maps in primary auditory cortex of the cat
Authors: Imig Thomas J. , Brugge John F. 
Published: January 2005

AbstractThe distributions of sources and terminals of callosal fibers in the high‐frequency representation of AI were related to binaural and frequency maps in combined anatomical and electrophysiological experiments. Sources of callosal axons were retrogradely labeled with HRP. Distributions of axon terminals were determined by autoradiographic labelling with [3H]‐proline and anterograde degeneration following callosal section. Regions in which cells exhibit summation or ipsilateral dominance and suppression contain higher concentrations of sources and terminals of callosal fibers than do regions in which cells exhibit monaural contralateral responses or contralateral dominance and suppression. Callosal axon terminals aggregate into columns. In Sections cut parallel to the cortical surface callosal columns take on complex forms that exhibit certain consistent features. Two prominent elongated columns separated by a narrow zone of sparse callosal innervation run in a rostrodorsal to caudoventral direction through AI crossing several octaves of the frequency representation. Ventral to these columns, along the AI‐AII border, less densely labeled callosal columns are in evidence. Low frequency representations of AI are interconnected but details of their innervation patterns were not worked out. Outside of AI there are regions that contain complex configurations of callosal columns. Several morphologically distinct types of neurons, located in laminae III through VI, were retrogradely labeled following injections of HRP into the opposite AI. About 94% of callosal neurons are pyramidal cells of layers III and IV.
An electron microscope study of the early postnatal development of the visual cortex of the hooded rat
Authors: Juraska Janice M. , Fifková Eva 
Published: January 2005

AbstractSynaptic plasticity in response to environmental events has been clearly demonstrated in the visual cortex of the rat, but no detailed data concerning the course of early synaptogenesis in this area are available. In this study, synaptogenesis in the visual cortex of hooded rats at 1, 3, 5, 7 and 10 postnatal days of age (P1‐P10) was examined with electron microscopy. The cortex was divided into the molecular layer, the superficial layers (II‐IV) and deep layers (V‐VI). In the visual cortex at P1, very few synapses are present in the molecular and deep layers and virtually none in the yet undifferentiated layers II‐IV that compose the cortical plate at this age. The synapses that are present are axodendritic and often symmetrical with little membrane thickening and few vesicles. Axosomatic synapses were seen as early as P3 but very rarely. There are marked increases in axodendritic synaptic density and maturity with increasing age. By P7 and P10, many synapses appear mature in form and the majority can be classified as asymmetrical. Axospinal synapses first appeared at P7 and were more frequent by P10. However, this classification was somewhat uncertain since no spinal apparatus was detected. Rate of synaptogenesis appeared to increase over the ages studied and showed no signs of leveling off except in the deep layers. Synaptic length was extremely variable and did not change systematically with age.
The organization of the electromotor nucleus and extraocular motor nuclei in the stargazer (Astroscopus y‐graecum)
Authors: Leonard R. B. , Willis W. D. 
Published: January 2005

AbstractThe organization of the oculomotor and electromotor systems was examined in the stragazer, a teleost. The electromotor system in these animals is a derivative of the oculomotor system. The extraocular motor nuclei and nerves consist of approximately equal numbers of motoneurons and axons (about 100 per muscle). In contrast, electromotor axons appear to branch several times within the intracranial portion of the IIIrd nerve. The topographical organization of the motoneurons was examined using retrograde transport of horseradish peroxidase injected into the electric organ or eye muscles. Electromotor and oculomotor neurons form distinct populations. Each electric organ receives a strong ipsilateral and a weak contralateral innervation. Individual eye muscles receive unilateral innervations with the expected laterality. Within the oculomotor nucleus there is some topographical separation of motoneurons innervating each muscle. Antidromic field potentials confirm the identity of the electromotor nucleus.
An autoradiographic study of the efferent connections of the ventromedial nucleus of the hypothalamus
Authors: Krieger Monica S. , Conrad Lily C. A. , Pfaff Donald W. 
Published: January 2005

AbstractEfferent projections from the ventromedial nucleus of the hypothalamus (VMN) were traced using tritiated amino acid autoradiography in albino rats.Ascending fibers passed through the anterior hypothalamus. Labelled fibers and terminal fields were seen in the preoptic area, bed nucleus of the stria terminalis, substantia innominata, the anterior amygdaloid area, diagonal bands of Broca and lateral septum. Fibers also projected laterally from VMN and entered the supraoptic commissures and zona incerta. These lateral projections were responsible for the fibers observed in the cerebral peduncle, the amygdala, the thalamus and the reticular formation. Fibers descending in a medial position projected through the posterior hypothalamus and then swept dorsally to terminate in the mesencephalic and pontine central grey. A projection from VMN into the median eminence was noted. The overall patterns of projection from different parts of VMN were similar; differences that existed were primarily in the relative strengths of the different projections.The efferent projections from VMN are extensive, well organized, and would appear capable of supporting significant physiological actions on extra‐hypothalamic structures.
Conduction velocity distribution of the retinal input to the hamster's superior colliculus and a correlation with receptive field characteristics
Authors: Rhoades Robert W. , Chalupa Leo M. 
Published: January 2005

AbstractCells driven reliably by shocks delivered to the optic nerve or optic chiasm were encountered throughout the depth of the colliculus. The incidence of such cells, however, decreased markedly in the laminae ventral to the stratum opticum. The distribution of conduction velocities for the retinal afferents to the tectum was quite broad (range: 1.7‐25.5 m/sec) and clearly biomodal with peaks at about 6 and 12 m/sec. A small number of cells were innervated by rapidly (> 15 m/sec) conducting axons. No evidence of an indirect‐fast pathway from the retina to the colliculus via the lateral geniculate nucleus and visual cortex was obtained. Afferent conduction velocity was not correlated with retinal eccentricity, collicular depth or speed selectivity. It was, however, clearly related to directional selectivity. Ninety percent of the tectal neurons receiving inputs from axons having conduction velocities of less than 5 m/sec were directionally selective while only 41% of those neurons innervated by more rapidly conducting fibers (> 5 m/sec) exhibited selectivity.One hundred and sixteen cells in the anterior portion of the colliculus were tested with shocks delivered to the ipsilateral optic nerve and photic stimulation of the ipsilateral eye. Of these, 11% exhibited some degree of binocularity and only 6% were responsive to optic nerve shocks. These electrophysiological findings were correlated with the limited nature of the retinal input to the ipsilateral superior colliculus.
Projections from the spinal and the principal sensory nuclei of the trigeminal nerve to the cerebellar cortex in the cat, as studied by retrograde transport of horseradish peroxidase
Authors: Ikeda Michiko 
Published: January 2005

AbstractProjections from the spinal (Vsp) and the principal sensory (Vp) nuclei of the trigeminal nerve to the cerebellar cortex were studied by means of retrograde transport of horseradish peroxidase in the cat.Neurons projecting to the simple lobule and the dorsal part of the paramedian lobule (PMD) were located mainly in the dorsal part of the nucleus interpolaris (Vi) and of the caudal one third of the nucleus oralis (Vo) and in the rostralmost part of the Vo. Neurons projecting to the medial part of the posterior folia of crus II (crus IIp) were located in the dorsal to ventral parts of the Vi and of the caudal one third of the Vo and in the rostralmost part of the Vo, while those projecting to the lateral part of crus IIp were confined to the ventral part of the Vi and of the caudal one third of the Vo. Neurons of the Vp also projected to all of these cortical areas. They were relatively confined to the ventral part of this nucleus. These trigeminocerebellar projections were exclusively ipsilateral to the cell origin. There were sparse projections from the Vi and Vo to lobules V to VIIIa. In addition, a small group of neurons in the subnucleus magnocellularis of the nucleus caudalis of the Vsp also projected to the above cortical areas. No projections were, however, observed to the anterior portion of the anterior lobe, crus I, the anterior folia of crus II, paraflocculus, flocculus and the ventral part of the PMD. The majority of these cerebellar pojection neurons were medium‐sized and triangular, fusiform or ovoid in shape. There were small neurons of similar types and large multipolar neurons as well.
The effect of hemidecortication on the inhibitory interactions in the superior colliculus of the cat
Authors: Buchtel H. A. , Camarda R. , Rizzolatti G. , Scandolara C. 
Published: January 2005

AbstractSingle neurons were recorded extracellularly from the superficial layers of the superior colliculus (SC) in 21 curarized cats. Four animals were normal unoperated cats, 17 were animals in which all cortical visual areas were ablated on one side from 7 to 69 days before the electrophysiological experiments. After cortical ablation all animals were blind in the visual field contralateral to the ablated side.In both normal and hemianopsic cats the effect of a visual stimulus located very far from the excitatory part of the unit receptive field, on the neuron responses to visual stimuli was studied. The remote stimulus (extra‐field stimulus) was a hand moved black spot 10° in diameter.In normal animals the introduction of the extra‐field stimulus in the hemifield contralateral or ipsilateral to the recorded SC produced a marked reduction of unit responses to visual stimuli presented in their receptive field. This effect was particularly strong when the extra‐field stimuli were introduced in the hemifield contralateral to the recorded side.In the hemianopsic animals the neurons of the SC ipsilateral to the lesion (receptive fields in the behaviorally blind hemifield) responded well to visual stimuli, but were only weakly inhibited by the extra‐field stimuli presented in the blind hemifield. The neurons of this colliculus with the exception of those in the upper part of stratum griseum superficiale were normally inhibited by stimuli presented in the normal hemifield.The neurons of the SC contralateral to the lesion responded well to visual stimuli and were normally inhibited by stimuli presented in the normal hemifield; they were virtually not affected by stimuli presented in the blind hemifield.Mechanisms responsible for the abnormal inhibitory interactions between and within colliculi after cortical lesions and the possible behavioral implications of the findings are discussed.
Axonal guidance during embryogenesis and regeneration in the spinal cord of the newt: The blueprint hypothesis of neuronal pathway patterning
Authors: Singer Marcus , Nordlander Ruth H. , Egar Margaret 
Published: January 2005

AbstractIn our previous studies on spinal cord regeneration in the adult lizard and the newt, we observed that the radial processes of the regenerating ependyma form between them channels which are subsequently invaded by growing neurites. In the present study we compare embryogenesis of the newt spinal cord with regeneration in the adult. Except for minor differences, we observed that the germinal neuroepithelium of the embryo and larva patterns the longitudinal neural tracts in a similar manner. With these facts in mind we propose the blueprint hypothesis which asserts that inherent in the primitive germinal neuroepithelium and its derivative primitive glia is the pattern of the primary neuronal pathways which is expressed in neurogenesis as formed channels or spaces between the processes of the epithelial cells, the surfaces of which contain trace pathways which the growing neurites follow toward their destination. The trace pathways are envisioned as mechanical‐chemical itineraries which the neurites follow according to their individual affinities. The hypothesis is compared to extant theories and the limitations in central nervous regeneration of vertebrates is compared.
Topographic projections of the retina and optic tectum upon the ventral lateral geniculate nucleus in the chick
Authors: Crossland W. J. , Uchwat C. J. 
Published: January 2005

AbstractThe topographic projections of the retina upon the optic tectum and ventral lateral geniculate nucleus (GLv) of the chick were investigated by making small intraretinal injections of 3H‐proline. The retinotectal projection pattern was similar to that described for the pigeon. The retinal projection to the GLv was also topographic and was restricted to the outermost lamina of the nucleus. The anteroposterior retinal axis was reversed in the GLv relative to its orientation in the tectum but the superoinferior axis was oriented identically in both. Furthermore, the posterior retina had an enlarged area of projection in the GLv similar to the enlarged area of retinotectal projection for the “red field” found in pigeons. The tectogeniculate projection was topographic and was confined to the outermost geniculate lamina. The secondorder retionotopic map made by the tectogeniculate projections was in register with the retinogeniculate projection. Although the retinal and tectal projection areas were coextensive in the outermost geniculate lamina, the grain density distributions peaked at different points along a radial path through the geniculate laminae. Injections of HRP into the optic tectum led to very light retrograde labeling of a small population of GLv cells topographically corresponding to the tectogeniculate projection zone of the injection site. The data suggest that the chick GLv is comparable to the GLv of other non‐primate mammals.
The distribution and size of ganglion cells in the retina of the pigmented rabbit: A quantitative analysis
Authors: Provis Jan M. 
Published: January 2005

AbstractThe distribution and soma diameters of retinal ganglion cells have been examined in whole mounted retinae of pigmented rabbits. Maps of the distribution of ganglion cells confirmed several features of earlier descriptions, but generally showed lower density values and yielded lower total ganglion cell counts (250,000–270,000). The maximum ganglion cell density encountered in each retina and its retinal location both varied between rabbits. As previously reported, the dominant feature of the rabbit's retina is a strongly developed visual streak (Hughes, '71) but some evidence of an area centralis‐like specialization was found. This appears not as the area of peak ganglion cell density, but as a concentration of large (≥20 μm in diameter) ganglion cells at the temporal end of the visual streak, 2‐3 mm from the temporal margin of the retina. In one rabbit in which the optic tract was sectioned five months previously, the density distribution of large retinal ganglion cells in the retinae has been mapped. These maps indicate that the nasotemporal division for large ganglion cells in the rabbit retina is approximately centered on the area of their maximum density. It has previously been reported that in the cat the area centralis is characterized by an aggregation of smaller diameter ganglion cells of a particular functional type (Stone, '65, '78). It is possible that areas of retina which subserve area centralis‐like functions are represented not simply by localized increases in ganglion cell density, but by changes in the relative proportions of ganglion cell types, which are reflected in the changing relative proportions of ganglion cell soma diameter groups.
Golgi studies on Purkinje cell development in the frog during spontaneous metamorphosis. II. Details of dendritic development
Authors: Uray Nándor J. , Gona Amos G. 
Published: January 2005

AbstractThe development of Purkinje cell dendrites was studied in the bullfrog from premetamorphic tadpoles to 10‐week‐old postmetamorphic froglets by the Golgi‐Kopsch method. In this species two distinct patterns of arbor formation may be seen, which appear to be related to differences in the timing of initial dendritic development. In Purkinje cells that begin development in early tadpole stages, the dendritic tree is elaborated by continuous and concomitant growth and branching, a process by which the developing arbor expands in both height and width. Arbor formation in Purkinje cells that begin development in metamorphosing tadpoles proceeds in two separate steps. Initially, dendrites of such cells elongate, but form only a few poorly developed branches; only when the arbor reaches near‐adult height does branching become extensive. Additional differences present in Purkinje cells are reflected in the paucity of growth cones and filopodia in the tadpole, and numerous filopodia and growth cones in the metamorphic period. An interesting feature of dendritic development in this species is a tendency to alter the arboreal domain by the formation of extra‐arboreal dendrites, and possibly by the occasional resorbtion of other partially formed dendrites.The pattern of dendritic development in the frog is different than in mammals and is difficult to interpret. Such unusual development may be due to disturbances in the timing of the formation of Purkinje cell dendrites and of the establishment of the external granular layer (EGL).
Retinal synaptic arrays: Continuing development in the adult goldfish
Authors: Fisher Leslie J. , Easter Stephen S. 
Published: January 2005

AbstractWe report a light‐ and electron‐microscopic examination of the inner plexiform layer of the central retina of young (c. 1 year) and old (3–4 year) goldfish. There were no new neurons added to this region during the growth period. Nonetheless, there were substantially more synapses (per cell, per mm2, or per degree2) in the older retinas. This result is discussed in the contexts of retinal function and neural development.
Retinotopic organization of areas 18 and 19 in the cat
Authors: Tusa R. J. , Rosenquist A. C. , Palmer L. A. 
Published: January 2005

AbstractThe location and retinotopic organization of areas 18 and 19 in cat cortex were determined using electrophysiological mapping techniques. These two areas each contain a single representation of the visual hemifield and each has a distinctive cytoarchitecture. The visual hemifield representations in these two areas are nearly mirror images of each other. Compared to area 17, areas 18 and 19 have less cortical surface area, have a lower cortical magnification factor, contain less of the visual field and contain second order instead of first order transformations of the visual hemifield. An unusual asymmetry was found between the representations of the upper and lower visual quadrants not seen before in maps of other areas of cat or other species. A considerable amount of variability in the retinotopic organization of these two areas was found among cats.
Development of neocortical circuitry: Histochemical localization of acetylcholinesterase in relation to the cell layers of rat somatosensory cortex
Authors: Kristt Donald A. 
Published: January 2005

AbstractAcetylcholineserase (AchE) was istochemically localized in neocorex cerebri of newborn to 1‐week‐old rats. At birth AchE‐dependent staining is limited to scaerd somata (Cajal‐Retzius cells) in the marginal zone and a few fibers and somata in primordial layer VI. By the end of the first week, neuronal elements are relatively well sained in pzrticular cell laminae, giving th appearance of three horizontal AchE‐rich “bands” which alternate with AchE‐poor laminae. The subpial band (layer I) is a narrow tangential zone of intensel saining fibers and scatered somata. The mid‐corical band contains an AchE‐positive fiber plexus (primordial layer IV) and numerous stained somata (pyramids of primordial layer V). In layer IV of the SmI region, intermittent foci of staining are noted which overlap the barels' distribution in the barrel field. The deep cortical band (bottom of primordial layer VI) consists of numerous stained somata (Marinotti cells). It is concluded that there is a laminar patern of acetylcholinesterase‐dependent staining in postanatal rat somatosensory corex, and that the laminar pattern bears a consistent spatial relation both to the cell layers and to the depths of high synapse density in immature cortex.