bluuebunny/crossref_metadata_2025 huggingface dataset:
Heterogeneity in the pattern of distribution of the axonal collaterals of Purkinje cells in zone b of the cat's vermis: An intracellular HRP study
Authors: Bishop Georgia A. , O'Donoghue Daniel L.
Published: January 2005

Intracellular recordings were obtained from Purkinje cells located in zone b of the vermis; all of the cells were located within lobule V. The ulnar and sciatic nerves were stimulated bilaterally in order to determine the input characteristics of each impaled neuron. Subsequent to recording physiological data the neurons were intracellularly labeled with horseradish peroxidase (HRP). At the conclusion of the experiment the animals were perfused and their brains were processed for HRP histochemistry. Zone b was divided histologically into five 200‐μm intervals and the location of each intracellularly injected Purkinje cell relative to these intervals was determined. The input characteristics of Purkinje cells within a single 200‐μm interval are not identical. Some Purkinje cells respond exclusively to input from a specific limb, whereas other Purkinje cells within the same interval are activated by both forelimb and hindlimb stimulation. The collaterals of a zone b Purkinje cell form a dense plexus at the Purkinje cell‐granule cell junction; branches also distribute to the superficial and deep granule cell layer, as well as to the lower molecular layer. Two patterns of collateral distribution were observed. In one pattern, the plexus has a single arbor confined to the vicinity of the cell body of origin. In the second pattern, at least two arborizations are present. One arbor remains within the vicinity of the cell body of origin whereas other arbors are distant from the parent cell; the two arbors are separated by areas devoid of collaterals. An analysis of the distribution of axonal varicosities shows that they are not uniformly distribution around the cell body of origin in either the sagittal or transverse plane. Cortical areas that contain numerous beads are interspersed between regions that contain few or no varicosities. The discontinuous pattern of distribution and the presence of varicosities in all three cortical laminae suggest that Purkinje cells in zone b have multiple discrete foci of influence on diverse populations of cerebellar neurons.

These anatomical findings suggest that individual Purkinje cells may play different functional roles in the local circuitry of zone b. Cells with the spatially confined arbors may be involved with the integration of information within restricted sagittal intervals (approximately 200 μm in width) of the cerebellum. Purkinje cells with the dual arbors have the potential to integrate information over a greater extent of zone b or, in some cases, between zone b and adjacent cortical zones (e.g., c1 or x).
Restoration of neuromuscular specificity following ventral rhizotomy in the bullfrog tadpole, rana catesbeiana
Authors: Farel Paul B. , Bemelmans Sibyl E.
Published: January 2005

The specificity of hindlimb reinnervation following transection of lumbar ventral roots was investigated in adult and larval bullfrogs (Rana catesbeiana). Five to 6 weeks following ventral rhizotomy, the retrogradely transported marker horseradish peroxidase (HRP) was applied to circumscribed regions of the hindlimb. The location of labeled motoneuron somata within the lumbar lateral motor column was compared with that obtained in unoperated tadpoles. Reinnervation of the hindlimb was largely specific in tadpoles operated during the first third of larval life. However, localization was largely lost in older tadpoles and adult frogs. Repeated applications of 3H‐thymidine combined with retrograde labeling with HRP failed to provide evidence that newly born motoneurons contribute to reinnervation of the hindlimb. Hindlimb reinnervation thus appears to result from regeneration of transected motor axons.

In contrast to the lack of neuromuscular specificity seen in older animals after transection of ventral roots, moteneuron axons disconnected from their targets by crush injury regenerate to the appropriate limb regions.
Distribution and ultrastructure of synapses on a premotor local nonspiking interneuron of the crayfish
Authors: Kondoh Y. , Hisada M.
Published: January 2005

Many premotor local nonspiking interneurons are involved in the control of the uropod movements of a crayfish. One of these interneurons was impaled intracellularly, characterized physiologically, and then labeled by intracellular horseradish peroxidase (HRP) injection to examine the distribution and ultrastructure of synapses. Depolarization of this interneuron by a current injection excited the closer motoneurons of the uropod and inhibited its opener motoneurons, but hyperpolarization had no effect. Input and output synapses are distributed all over the major branches and the finer neurites except for the main neurite (7–10 μm in diameter), which runs near the dorsal surface of the neuropil. Both types of synapse are located on the same neurite and are often intermingled in close proximity, often less than 1 μm apart. Presynaptic terminals of the interneuron contain round, clear vesicles that are densely packed in fine branches and spines. The number of synaptic vesicles associated with a particular output synapse was estimated to be about 2,000. No dense‐cored granules are observed in the labeled neurites. Our results support the proposal that synaptic transmission in this class of interneurons of the crayfish can sometimes be restricted to a very small region of the branches and that, therefore, different regions of the interneuron can function independently.
Monoclonal antibodies to the turtle cortex reveal neuronal subsets, antigenic cross‐reactivity with the mammalian neocortex, and forebrain structures sharing a pallial derivation
Authors: Kriegstein Arnold R. , Shen Janet M. , Eshhar Nomi
Published: January 2005

The dorsal cortex of the pond turtle (Pseudemys scripta) is a relatively simple structure consisting of two principal classes of neurons that occupy three distinct layers. Morphological, pharmacological, and physiological data suggest many similarities to the mammalian neocortex, rendering it an interesting preparation for comparative studies. We prepared monoclonal antibodies to the turtle dorsal cortex by immunizing mice with cortical tissue from adult turtles. Twelve antibodies were generated that recognize specific components of the turtle cortex. Among these, eight antibodies label only neurons and four label only ependymal glial cells. Differences in tissue staining pattern and immunoglobulin class suggest a heterogeneity of antigenic specificity among the antibodies.

The staining patterns of three of our antibodies are described. TC3, like all other neuron‐marking antibodies generated, labels a subset of both pyramidal and stellate cell types. It also cross‐reacts with a subset of mammalian cortical neurons and labels them with a pattern similar to that observed in the turtle cortex. TC5 stains ependymal cells and their glial processes in the turtle cortex, and cross‐reacts with fibrous astrocytelike processes in mammalian neocortical white matter. TC9 appears to recognize antigens of neurons sharing a pallial derivation in turtle.
Glial patterns during early development of antennal lobes of Manduca sexta: A comparison between normal lobes and lobes deprived of antennal axons
Authors: Oland Lynne A. , Tolbert Leslie P.
Published: January 2005

The synaptic neuropil of the olfactory (antennal) lobe of the moth Manduca sexta is subdivided into histologically conspicuous structures called glomeruli that are typical of olfactory systems in vertebrates and invertebrates. Each glomerulus consists of the highly branched neuritic arbors of both primary olfactory axons and antennal‐lobe neurons, bounded by a nearly complete envelope of glial cells. We have studied events occurring during the first half of metamorphic adult development. The first signs of organization of the neuropil into glomeruli are changes in glial cells. Prior to the ingrowth of olfactory axons from the antenna, glial cells form a continuous border around the neuropil. When olfactory axons begin to reach the lobe, glial cells embark on a stereotyped series of changes: the border becomes disrupted, glial cells begin to proliferate and extend processes into the outer regions of the neuropil, and some glial cells migrate toward the center of the neuropil. Shortly thereafter, glomeruli emerge from the neuropil, delineated by glial cells. If, however, afferent axons are prevented from ever reaching the antennal lobe, glomeruli never develop and the glial cells remain almost entirely restricted to a thick layer bordering the neuropil. Thus sensory axons have a direct influence not only on neuronal but also on glial differentiation. Our results lead us to suggest that the glial cells may be in a position to act as intermediaries in developmental interactions between sensory axons and antennal‐lobe neurons.
Topographic organization of the orientation column system in large flat‐mounts of the cat visual cortex: A 2‐deoxyglucose study
Authors: Löwel Siegeid , Freeman Brian , Singer Wolf
Published: January 2005

We developed a flat‐mount technique in order to visualize, without additional reconstruction, the system of orientation columns in the cat visual cortex by using 2‐deoxyglucose‐autoradiography.

Experimental animals were injected with 2‐deoxyglucose and then stimulated for 45–60 minutes either with vertical or horizontal or oblique gratings alone or with vertical and horizontal gratings presented in alternation.

In both areas 17 and 18 stimulation with either vertical or horizontal or oblique stripes produced similar and highly ordered patterns of parallel bands of increased 2‐deoxyglucose uptake that were perpendicular to the boundaries of the areas. In area 17 they occasionally extended without interruption from the 17/18 border on the top of the lateral gyrus to the monocular segment in the splenial sulcus. Superposition of serial sections revealed that these bands were present in all cortical layers and in precise register along lines orthogonal to the lamination. The center‐to‐center spacing of the bands was 1.0–1.1 mm in area 17 and 1.2–1.4 mm in area 18. Stimulation with alternating vertical and horizontal contours led to a pattern the general organization of which resembled that induced by a single orientation but the spacing of which was reduced by a factor of 0.5. This strongly supports the concept that orientation is mapped in a system of parallel bands and argues against a recently formulated hypothesis that iso‐orientation bands extend like spokes from centers that lack orientation selectivity (Braitenberg and Braitenberg, Biol. Cybern, 33:179–186, '79).

Another characteristic feature, revealed by the flat‐mount technique, was a periodic variation of 2‐deoxyglucose uptake along the bands that gave them a beaded appearance. The mean center‐to‐center distance between adjacent beads on the same band was in the range of 0.9–1.2 mm and remained unchanged when horizontal and vertical gratings were presented in alternation. We propose that these beads reflect another columnar system whose features have yet to be determined.
Time course of the reaction of glial fibers in the somatosensory thalamus after lesions in the dorsal column nuclei
Authors: Wells Joseph , Tripp Leslie N.
Published: January 2005

These experiments were designed to examine the relationship of glial hypertrophy to the time course of reactive synaptogenesis in the ventral posterolateral nucleus of the rat thalamus after lesions in the dorsal column nuclei. Because synaptogenesis is delayed for 30 days following lesions of the dorsal column nuclei, the initial hypertrophy of the glial processes in response to degeneration can be separated temporally from synaptogenesis. Glial hypertrophy was determined by measuring the relative area of neuropil occupied by profiles of glial processes on electron micrographs. The initial glial hypertrophy reached its peak 2 days after the lesion. However, at the time when synaptogenesis began, the area of neuropil occupied by glial processes was less than normal. When synaptogenesis was complete, the area of glial profiles also returned to normal. The role of glia in synaptogenesis was clearly different from its role in response to degeneration. In those systems such as the hippocampus, in which reactive synaptogenesis starts early in the recovery sequence, the relationship of glia to synaptogenesis may be masked by the glial response to degeneration.

Hypertrophy of glial processes after lesions of other afferent pathways to the ventral posterolateral nucleus was compared to the hypertrophy following lesions of the dorsal column nuclei in order to see if there was a special relationship between glia and the lemniscal afferents to the ventral posterolateral nucleus. Lesions were placed in the medial lemniscus, somatosensory cortex, and the mesencephalon in addition to the dorsal column nuclei. The area of neuropil occupied by the glial processes expanded markedly after each of the lesions. The initial glial hypertrophy was relatively independent of the size of the lesion in the dorsal column nuclei, the degree of degeneration in the ventral posterolateral nucleus, the proximity of the lesion to the ventral posterolateral nucleus, and the site of the lesion.
Postembryonic neurogenesis in the CNS of the tobacco hornworm, Manduca sexta. I. Neuroblast arrays and the fate of their progeny during metamorphosis
Authors: Booker Ronald , Truman James W.
Published: January 2005

The tobacco hornworm Manduca sexta exhibits dramatic changes in its body morphology and behavior as it is transformed from a larva into an adult during metamorphosis. Accompanying these changes is an extensive reorganization of this moth's central nervous system (CNS), which involves both the death and remodeling of subsets of larval neurons. We report here that the segmental ganglia of the larvae also contain a stereotyped array of identifiable neuronal stem cells (neuroblasts) that contribute over 2,000 cells to each thoracic ganglion and about 40–80 cells to each abdominal ganglion. The distribution of these neuroblasts varies in a segment specific manner. Dormant neuroblasts are found adjacent to the neuropil in late embryos and early first instar larvae. After the molt to the second instar, these cells enlarge and begin to divide. Through a series of asymmetrical divisions, each neuroblast generates a discrete nest of 10–90 progeny by the end of larval life. These progeny (the imaginal nest cells) are developmentally arrested at an early stage of differentiation and remain so until metamorphosis. At the onset of metamorphosis, a wave of cell death sweeps through the nests, the extent of the death being much greater within the abdominal nests than in the thoracic nests. The surviving imaginal nest cells then differentiate to become functional neurons that are incorporated into the adult CNS.
Hair cell innervation by spiral ganglion neurons in the mouse
Authors: Berglund A. M. , Ryugo D. K.
Published: January 2005

Horseradish peroxidase (HRP) was injected extracellularly into the auditory nerve of adult mice so that the enzyme could infuse individual spiral ganglion neurons. Forty‐two well‐stained neurons were reconstructed through serial sections from their cell bodies to peripheral terminations in the organ of Corti with the aid of a light microscope and drawing tube. No neuron was observed to innervate both inner and outer hair cells (IHCs and OHCs). Previous observations from neonatal mammals that reported that IHCs and OHCs were innervated by the same neuron are thus presumed to describe a transient developmental phenomenon.

Two populations of spiral ganglion neurons were determined on the basis of the differences in receptor innervation. The type I neurons innervated exclusively IHCs by way of thick (1–2 μm) radial fibers, whereas the type II neurons innervated only OHCs by way of thin (∼0.5 μm) outer spiral fibers. Certain features of the peripheral process in the vicinity of the cell body were highly correlated with fiber type. This pattern of separate innervation of IHCs and OHCs by type I and type II neurons, respectively, may represent the general plan of afferent organization for the adult mammalian cochlea.
Topography of the corticofugal projection to the lateral reticular nucleus in the monkey
Authors: Wiesendanger R. , Wiesendanger M.
Published: January 2005

The cortical projection to the lateral reticular nucleus (LRN) was explored in monkeys prepared for autoradiography and horseradish peroxidase (HRP) histochemistry. An unambiguous projection was revealed only in cases with injections of the precentral forelimb and hindlimb areas. The forelimb area projection occupied centromedial segments, the hindlimb area projection occupied ventrolateral segments of the LRN with very little overlap. Some sparse labeling was also seen with injections of the supplementary motor area (SMA), but only when the lectin‐bound tracer HRP was injected and not when autoradiography was used. Retrogradely labeled cortical cells occupied a larger cortical area in one case with injection of free HRP into the LRN. Since the additional expanse of cortex, however, was not examined in anterograde cases, and since the injected marker substance had diffused to neighboring structures, the significance of the labeled cells outside the precentral motor cortex is questionable. There was no evidence for a projection from the precentral face area with either anterograde tracing method. The corticoreticular projection was bilateral and only slightly more marked contralateral to the injection. The labeling was largely confined to the magnocellular division with minor amounts in the parvicellular division (especially in the hindlimb cases). The subtrigeminal portion was spared in all cases. It is concluded that the LRN constitutes another somatotopically organized precerebellar nucleus relaying signals from the motor cortex to the cerebellum. Compared with the corticopontocerebellar parthway in monkeys, however, the LRN is only a minor component of the corticocerebellar transmission system.
Structural features of the terminal loop region of frog retinal rod outer segment disk membranes: I. Organization of lipid components
Authors: Corless Joseph M. , Fetter Richard D. , Costello M. Joseph
Published: January 2005

We have applied thin sectioning and freeze‐fracture techniques to investigate the terminal loop structure of photoreceptive disks in frog retinal rod outer segments. Our studies of this region demonstrate a highly curved terminal loop bilayer that is continuous with both lamellar bilayers of the disk, and equivalent to them in dimensions and staining properties. Rhodopsin, however, appears to be excluded from this region of high curvature.
Distribution of carbonic anhydrase activity in neurons of the rat
Authors: Wong Vivien , Barrett Charles P. , Donati Edward J. , Guth Lloyd
Published: January 2005

Certain neurons of dorsal root ganglia (DRG) and some fibers of the sciatic nerve contain histochemically demonstrable carbonic anhydrase activity. Since the distribution of this enzyme throughout the nervous system has not yet been evaluated systematically, we conducted a comprehensive histochemical survey focusing particularly on structures derived from the neural crest and nonneural crest ectoderm. In the peripheral nervous system, we observed carbonic anhydrase activity in some, but not all, neurons of dorsal root, trigeminal, celiac, and myenteric ganglia as well as in glial cells throughout the CNS. Some neurons of the nodose ganglion also showed carbonic anhydrase activity. In all first order sensory ganglia that were studied, the enzyme was found only in large (50 μm or above) and medium (20–50 μm) size neurons; in the case of spinal ganglia, the reactive neurons constituted approximately 30% of the total neuronal population. Of these reactive neurons, 56% were heavily stained and 44% were moderately stained. Several possible roles for neuronal carbonic anhydrase are considered.
Serotonin and dopamine in the retina of a lizard
Authors: Engbretson Gustav A. , Battelle Barbara‐Anne
Published: January 2005

The objective of this paper is to report the presence and localization of serotonin and dopamine in the retina of the lizard Uta stansburiana. High performance liquid chromatography and electrochemical detection were used to identify and quantitate the two amines. Both compounds are present as endogenous molecules in this retina and are found in concentrations similar to those reported in other non‐mammalian retinas. The same methods were employed to confirm, in the isolated retina, the synthesis of serotonin from precursor, tryptophan.

Immunocytochemical methods were used to localize, in the neural retina, serotonin and the rate‐limiting enzyme of dopamine synthesis, tyrosine hydroxylase. Serotonin immunoreactivity was observed in bistratified amacrine cells (ca.7 μU dia.) with processes ramifying in sublayers 1,4, and 5 of the inner plexiform layer. Immunoreactivity to tyrosine hydroxylase was observed in a different population of bistratified amacrine cells (ca. 11 μ dia.) that had processes ramifying in sublayers 1 and 5 (and perhaps 3) of the inner plexiform layer. The enzymes for further metabolism of dopamine were not found in the retina of this lizard by immunocytochemical methods.

The results of this research suggest that only single classes of serotoninergic and dopaminergic neurons are present in the retina of U. stansburiana. This retina might, therefore be an appropriate place in which to investigate the functioning of these amines in visual information processing.
Action and location of neuropeptide tyrosine (Y) on hippocampal neurons of the rat in slice preparations
Authors: Haas H. L. , Hermann A. , Greene R. W. , Chan‐Palay V.
Published: January 2005

The action of bath applied NPY (1–1,000 nM) was investigated on hippocampal slices of the rat with extra‐and intracellular recording. Neuropeptide Y (NPY) at 10–1,000 nM caused a concentration‐dependent, long–lasting reduction of excitatory postsynaptic potentials (EPSPs) in the hippocampal subfield CA1 and the area dentata, and an even stronger reduction of population spikes. Paired pulse experiments with low intensity, stimulation‐evoked PSPs showed a marked increase in facilitation in the presence of NPY, indicating a presynaptic action. Spontaneous burst firing of CA1 pyramidal cells in low calcium, high magnesium medium was reduced, indicating a partially postsynaptic inhibitory action of NPY on their dendrites. Intracellular recording from CA1 somata during NPY administration revealed a reduction of the amplitudes of excitatory–inhibitory postsynaptic potential (EPSP–IPSP) sequences in the absence of changes in membrane potential and conductance. Accommodation of firing during long depolarizing pulses and afterhyperpolarizations were unchanged. The innervation pattern of NPY immunoreactive fibers in the same regions was studied in slices adjacent to the ones used for electrophysiology by using antisera against NPY and light and electron microscopy. There is a dense innervation of CA1 by NPY‐immunoreactive axons and terminals, particularly in the stratum moleculare. NPY‐immunoreactive neurons are present in the stratum oriens and pyramidale. The NPY labeled axons of the stratum moleculare participate in numerous synaptic contacts with the smaller dendritic elements in this layer, many of which belong to pyramidal neurons. These observations provide evidence for a dendritic NPY‐immunoreactive innervation of CA1 neurons, which is in keeping with the electrophysiological effects of NPY on pyramidal neurons. We conclude that NPY has inhibitory actions, presynaptically to reduce excitatory transmitter release and at a distal dendritic site to reduce postsynaptic excitability. The physiological significance of the NPY effects appears to be a long‐lasting depression of excitatory input to pyramidal cell dendrites controlled through local interneurons and through other extrinsic projections of NPY neurons from elsewhere in the brain.
Organization of intracortical and commissural connections in somatosensory cortical areas I and II in the raccoon
Authors: Herron Paul , Johnson John Irwin
Published: January 2005

The organization of intracortical and callosal projecting cell bodies was examined in somatosensory representation areas I (SI) and II (SII) of the raccoon by use of horseradish peroxidase (HRP) or horseradish peroxidase‐wheat germ agglutin (HRP‐WHA) HRP and HRP‐WHA were injected into commissurally and noncommissurally connected subdivisions of SI and SII. Injection sites in SII were identified electrophysiologically. Results were obtained from transverse sections in which the HRP was visualized with the aid of the substrates dihydrochlorobenzidine or tetramethyl benzidine in the presence of hydrogen peroxidase.

The principal findings were the following: (1) there are reciprocal connections between SI and SII; (2) in SI the intracortically projecting cell bodies and terminals are located primarily in sulcal cortex; (3) intracortically projecting neurons in SI are located primarily in layers III whereas in SII they are located principally in layers III and V; (4) there are connections between disparate areas within SI; and (5) there are intracortical connections between callosum‐connected and acallosal regions in SII. These results are discussed with regard to the results of mapping studies of the SI, the significance of intracortical connections to the formation of sulci in SI, and the possible roles of nonhomotopic connections in the intermanual transfer of learning.
Development of the precerebellar nuclei in the rat: III. The posterior precerebellar extramural migratory stream and the lateral reticular and external cuneate nuclei
Authors: Altman Joseph , Bayer Shirley A.
Published: January 2005

Sequential thymidine radiograms from rats injected on day E15 and killed thereafter at daily intervals up to day E22 were analyzed to trace the migratory routes and settling patterns of neurons of the lateral reticular nucleus and the external cuneate nucleus. The neurons of the lateral reticular and external cuneate nuclei originate in the primary precerebellar neuroepithelium at the same site as the inferior olivary neurons but follow a different migratory route. The labeled young neurons that are produced on day E15 (the last one‐third of the total) join the posterior precerebellar extramural migratory stream. The cells move circumferentially over the wall of the medulla in a ventral direction and by day E17 reach the midline and cross it beneath the inferior olive. The crossing cells apparently continue to migrate circumferentially on the opposite side. One complement of these cells begins to form a ventrolateral extramural condensation on day E19. By day E20 some cells begin to penetrate the parenchyma and settle as neurons of the lateral reticular nucleus. The settling of the lateral reticular neurons continues on the following day, and by day E22 all the cells destined for the lateral reticular nucleus have penetrated the parenchyma. A dorsomedial‐to‐ventrolateral neurogenetic gradient is indicated for the settling lateral reticular neurons.

Another complement of migrating cells continues dorsally and forms a condensation on day E19 that we interpret as the external cuneate component of the crossed stream. These cells begin to penetrate the parenchyma on day E20, and by days E21 and E22 two components of the external cuneate nucleus are identifiable–the dorsal and ventral external cuneate nuclei. The neurons of the lateral reticular and external cuneate nuclei differ from neurons of all the other precerebellar nuclei in that their cerebellar projection is predominantly ipsilateral. We speculate that the axons of all precerebellar neurons are genetically specified to cross the midline ventrally to provide a contralateral efferent projection, but this is modified in the case of the ipsilaterally projecting lateral reticular and external cuneate neurons by the cell bodies following their neurites to the opposite side.
Anesthetic state does not affect the map of the hand representation within area 3b somatosensory cortex in owl monkey
Authors: Stryker Michael P. , Jenkins William M. , Merzenich Michael M.
Published: January 2005

Receptive fields defined for small clusters of neurons within the middle cortical layers of area 3b differed little in size or in the skin locations represented among: (a) alert, (b) nitrous oxide‐anesthetized, (c) deep sodium pentobarbital‐anesthetized, and (d) ketamine‐anesthetized owl monkeys. Repeated recordings from nearly identical cortical loci yielded nearly identical multiunit receptive fields under different conditions of anesthesia.
Organization of postcranial kinesthetic projections to the ventrobasal thalamus in raccoons
Authors: Wiener Sidney I. , Johnson John Irwin , Ostapoff E.‐Michael
Published: January 2005

To determine the presence and organization of kinesthetic, as compared with other mechanosensory projection zones in the thalamus of raccoons, unit‐cluster responses to mechanical stimulation of the postcranial body were mapped electrophysiologically in the thalami of 14 raccoons anesthetized with Dial‐urethane. A distinct zone of kinesthetic projections (from receptive fields in muscles, tendons, and joints) was found in the rostral and dorsal aspects of the mechanosensory projection zone. These projections are somatotopically organized: those from axial structures lie dorsalmost and those from successively more distal limb regions are successively more caudoventral. The kinesthetic forelimb representation is large and lies rostrodorsal to a large central core of cutaneous projections from the forepaw digits. A few scattered kinesthetic projections were found at the caudal edge of the sensory thalamic region.

The large, spatially and somatotopically distinct kinesthetic projection zone in the thalamus parallels those seen in the cortex and medulla of raccoons. Similar findings in monkeys, and suggestions from data in cats and humans support the hypothesis of a distinct pathway to the cortex for kinesthetic information in all mammals.
A quantitative study of the distribution of neurons projecting to the precentral motor cortex in the monkey (M. fascicularis)
Authors: Ghosh S. , Brinkman C. , Porter R.
Published: January 2005

The relative numbers and locations of neurons projecting to the “fore‐limb” region of the precentral motor cortex were studied in three monkeys by using the retrograde transport of horseradish peroxidase. Within the forelimb area of the motor cortex itself, there are extensive and profuse interconnections. However, regions within this area receive afferents from very few neurons in other parts of the motor cortex representing hindlimb or head movements. Most of the motor cortical representation of the forelimb in the anterior bank of the central sulcus is devoid of callosal connections.

In both the ipsilateral and contralateral hemispheres, the premotor (lateral area 6) and supplementary motor (medial area 6) areas dominate quantitatively the inputs to the motor cortical representation of the forelimb. The afferents from the premotor area are restricted and come from a region immediately behind the arcuate spur and adjacent parts of the superior and inferior limbs of the arcuate sulcus in the floor, caudal bank, and caudal lip of that sulcus. From the supplementary motor area (SMA), afferents originate from its whole rostrocaudal extent. Thalamic nuclear regions projecting to a restricted zone in the anterior bank of the central sulcus are recipients of cerebellar and somatosensory outputs. Involvement of more anterior parts of the motor cortex by the tracer labels thalamocortical cells, which are targets of pallidal output also. Within the first somatosensory cortex, cytoarchitectonic areas 1, 2, and 3a project to area 4. The projection from area 3a may provide one pathway by which short‐latency peripheral inputs, especially from muscles, reach the motor cortex.
Quantitative autoradiographic maps of local cerebral glucose metabolism in awake rats: I. Septal region and anterior hypothalamus
Authors: Brainard George C. , Schwartzman Robert J. , Alexander Guillermo M.
Published: January 2005

Quantitative 14C‐deoxyglucose autoradiography was used to determine the local cerebral glucose metabolic rate (lCMRG) of nuclei in the septal region and anterior hypothalamus of awake, unanesthetized rats. The lCMRG of the medial and lateral septal areas, preoptic areas, medial preoptic nuclei, suprachiasmatic nuclei, supraoptic nuclei, anterior hypothalamic nuclei, and paraventricular nuclei were measured. The lCMRG of each nucleus was mapped at successive rostral‐caudal levels to determine significant internuclear and intranuclear variations. These data provide a detailed neuroanatomic map of cerebral energy metabolism of the septal and anterior hypothalamic regions in animals under standardized conditions.
Some anatomical observations on the projections from the hypothalamus to brainstem and spinal cord: An HRP and autoradiographic tracing study in the cat
Authors: Holstege Gert
Published: January 2005

The hypothalamus is closely involved in a wide variety of behavioral, autonomic, visceral, and endocrine functions. To find out which descending pathways are involved in these functions, we investigated them by horseradish peroxidase (HRP) and autoradiographic tracing techniques.

HRP injections at various levels of the spinal cord resulted in a nearly uniform distribution of HRP‐labeled neurons in most areas of the hypothalamus except for the anterior part. After HRP injections in the raphe magnus (NRM) and adjoining tegmentum the distribution of labeled neurons was again uniform, but many were found in the anterior hypothalamus as well. Injections of 3H‐leucine in the hypothalamus demonstrated that:

The anterior hypothalamic area sent many fibers through the medial forebrain bundle (MFB) to terminate in the ventral tegmental area of Tsai (VTA), the rostral raphe nuclei, the nucleus Edinger‐Westphal, the dorsal part of the substantia nigra, the periaqueductal gray (PAG), and the interpeduncular nuclei. Further caudally a lateral fiber stream (mainly derived from the lateral parts of the anterior hypothalamic area) distributed fibers to the parabrachial nuclei, nucleus subcoeruleus, locus coeruleus, the micturition‐coordinating region, the caudal brainstem lateral tegmentum, and the solitary and dorsal vagal nucleus. Furthermore., a medial fiber stream (mainly derived from the medial parts of the anterior hypothalamic area) distributed fibers to the superior central and dorsal raphe nucleus and to the NRM, nucleus raphe pallidus (NRP), and adjoining tegmentum.

The medial and posterior hypothalamic area including the paraventricular hypothalamic nucleus (PVN) sent fibers to approximately the same mesencephalic structures as the anterior hypothalamic area. Further caudally two different fiber bundles were observed. A medial stream distributed labeled fibers to the NRM, rostral NRP, the upper thoracic intermediolateral cell group, and spinal lamina X. A second and well‐defined fiber stream, probably derived from the PVN, distributed many fibers to specific parts of the lateral tegmental field, to the solitary and dorsal vagal nuclei, and, in the spinal cord, to lamina I and X, to the thoracolumbar and sacral intermediolateral cell column, and to the nucleus of Onuf.

The lateral hypothalamic area sent many labeled fibers to the lateral part of the brainstem and many terminated in the caudal brainstem lateral tegmentum, including the parabrachial nuclei, locus coeruleus, nucleus subcoeruleus, and the solitary and dorsal vagal nuclei. In the spinal cord labeled fibers were found in the intermediate zone, lamina X, and the thoracolumbar intermediolateral cell column.

A mediolateral organization of the hypothalamic projections to the caudal brainstem is proposed in which the PVN occupies a separate position.
Mode of growth of retinal axons within the tectum of Xenopus tadpoles, and implications in the ordered neuronal connection between the retina and the tectum
Authors: Fujisawa Hajime
Published: January 2005

Retinal axons of Xenopus tadpoles at various stages of larval development were filled with horseradish peroxidase (HRP), and their trajectories and the patterns of branching within the tectum were analyzed in whole‐mount preparations. To clarify temporal and spatial modes of growth of retinal axons during larval development, special attention was directed to labeling a restricted regional population of retinal axons with HRP, following reported procedures (H. Fujisawa, K. Watanabe, N. Tani, and Y. Ibata, Brain Res. 206:9–20, 1981; 206:21–26, 1981; H. Fujisawa, Dev. Growth Differ 26:545–553, 1984).

In developing tadpoles, individual retinal axons arrived at the tectum, without clear sprouting. Axonal sprouting first began when growing tips of each retinal axon had arrived at the vicinity of its site of normal innervation within the tectum. Thus, the terminals of the newly added retinal axons were retinotopically aligned within the tectum. The retinotopic alignment of the terminals may be due to an active choice of topographically appropriate tectal regions by growth cones of individual retinal axons.

The stereotyped alignment of the newly added retinal axons was followed by widespread axonal branching and preferential selection of those branches. Each retinal axon was sequentially bifurcated within the tectum, and old branches that had inevitably been left at ectopic parts of the tectum (owing to tectal growth) were retracted or degenerated in the following larval development. The above mode of axonal growth provides an adequate explanation of cellular mechanisms of terminal shifting of retinal axons within the tectum during development of retinotectal projection. Selection of appropriate branches may also lead to a reduction in the size of terminal arborization of retinal axons, resulting in a refinement in targeting.
Distribution of axons according to diameter in the monkey's optic tract
Authors: Reese B. E. , Guillery R. W.
Published: January 2005

The distribution of axonal diameters in the optic tract of Old World monkeys was examined by light and electron microscopy. Axon diameters were measured in samples of 100 axons taken from several locations in a cross section of the tract about 5 mm behind the optic chiasm. Fine‐caliber axons (<1.75 μm in diameter) were found in all parts of the tract. Dorsally no coarse axons were present. Further ventrally, coarse axons gradually appeared and increased steadily in proportion. The largest optic axons (>2.5 μm) were found in the most ventral parts of the tract, near the pial surface.

This pattern of segregation of axons of differing diameters in the optic tract is a rearrangement of the distribution of axon diameters seen in the nerve rather than a continuation of the same pattern. Examination of axon diameters in the optic nerve has shown that there is a preponderance of fine axons centrally, while coarser axons are found in the periphery, near the pial surface; however, histograms from central parts of the nerve contain a greater proportion of coarse axons than the dorsal parts of the optic tract, while histograms from the periphery of the optic nerve contain a conspicuously greater proportion of fine axons than do histograms from the most ventral parts of the tract. This relatively greater segregation of axons according to diameter in the optic tract demonstrates that the distribution of axons in the tract cannot be formed by the simple combination of two hemiretinal maps contained in each optic nerve, as suggested in classic descriptions.

The optic axons of different diameters are likely to arise from morphologically distinct retinal ganglion cell types. Previous studies in the cat have demonstrated that axons of differing diameter classes, which arise from the distinct retinal ganglion cell types, are distributed in a uniform fashion in the optic nerve but are partially segregated according to their diameter in the tract. This rearrangement of axons between the nerve and tract in carnivores has been related to the temporal gradient of neurogenesis of the different retinal ganglion cell classes, axonal order in the optic tract being an index of axonal arrival during development. We suggest that the same occurs in the development of the monkey's retinofugal system.
Primary afferent projections to the central octavus nuclei in the elasmobranch, Rhinobatos sp., as demonstrated by nerve degeneration
Authors: Dunn Robert F. , Koester David M.
Published: January 2005

Nerve degeneration studies were performed to determine the central projections of the octavus nerve in the guitarfish, Rhinobatos sp. Most first‐order octavus nerve afferents are confined to the ventral longitudinal column of the medulla, which consists of four octavus nuclei: the nucleus octavus anterior (NOA), nucleus octavus magnocellularis (NOM), nucleus octavus descendens (NOD); and nucleus octavus posterior (NOP). Central projections of the octavus nerve outside of the ventral octavus nuclear column are to the vestibulolateral lobe of the cerebellum, the large multipolar cells that lie deep to the cerebellar crest of nucleus intermedius, the reticular formation, and the nucleus octavolateralis efferens. In addition, the cytoarchitectural features of the four octavus nuclei have been analyzed: the NOA consists of large spindle‐shaped neurons and medium‐sized multipolar neurons; the NOM is a small nucleus consisting of very large multipolar neurons; the NOD contains several types of neurons including large spindle‐shaped neurons, large multipolar neurons, and polymorphic small and medium‐sized neurons; and the NOP contains small spherical and small multipolar neurons evenly distributed throughout the nucleus. On the basis of the morphology of the neurons, the NOA and NOD appear to have subdivisions suggesting a more complex organization of the octavus nuclear column than previously recognized.
Morphometric analysis of serotoninergic bipolar cells in the retina and its implications for retinal image processing
Authors: Schäutte Michael , Weiler Reto
Published: January 2005

The entire population of retinal serotoninergic bipolar cells in the turtle Pseudemys scripta elegans was labeled by immunocytochemical methods. This allowed a systematic analysis to be made of the morphological variabilities among a functionally homogeneous neuronal population. The analyzed morphological characteristics included: (1) size of the Landolt club, (2) size of the soma, (3) lateral extension of the ramification within the outer plexiform layer, (4) course of the axon across the inner nuclear layer, (5) pattern of the axonal ramification within the inner plexiform layer, (6) lateral extension of these ramifications, and (7) density of the cells.

Whereas characteristics 1–4 and 7 show a morphological variability strictly related to the location of the bipolar cell with respect to the visual streak, a fovealike structure, characteristics 5 and 6 show no such correlation. The size of the soma increases by a factor of 4 from the visual streak toward the periphery. The area covered by the ramification in the OPL increases from 330 μm2 at the visual streak to 50,000 μm2 at the dorsal and ventral edges of the retina. The coverage factor remains the same throughout the retina, as well as the area covered by the ramifications in the IPL, which is about 2,000 μm2. At the visual streak and at 110μ ventral and 68μ dorsal of the visual streak, the bipolar axons cross the INL perpendicularly. In between the axons take an oblique course leading to an axon‐induced shift between input and output of up to 250 μm. The density of cells has its maximum of about 8,000 cells/mm2 at the visual streak and its minimum of about 500 cells/mm2 at the dorsal and ventral periphery.

These morphometric data reveal a distorted projection from the outer plexiform layer onto the inner plexiform layer with an overrepresentation of the visual streak area. This helps to increase the visual acuity of this area and possibly supports motion detection.
Ectosylvian visual area of the cat: Location, retinotopic organization, and connections
Authors: Olson Carl R. , Graybiel Ann M.
Published: January 2005

We have mapped out the ectosylvian visual area (EVA) of the cat in a series of single‐ and multiunit recording studies. EVA occupies 10–20 mm2 of cortex at the posterior end of the horizontal limb of the anterior ectosylvian sulcus. EVA borders on somatosensory cortex anteriorly, auditory cortex posteriorly, and nonresponsive cortex laterally. EVA exhibits limited retinotopic organization, as indicated by the fact that receptive fields shift gradually with tangential travel of the microelectrode through cortex. However, a point‐to‐point representation of the complete visual hemifield is not present.

We have characterized the afferent and efferent connections of EVA by placing retrograde and anterograde tracer deposits in EVA and in other cortical visual areas. The strongest transcortical fiber projection to EVA arises in the lateral suprasylvian visual areas. Area 20, the granular insula, and perirhinal cortex provide additional sparse afferents. The projection from lateral suprasylvian cortex to EVA arises predominantly in layer 3 and terminates in layer 4. EVA projects reciprocally to all cortical areas from which it receives input. The projection from EVA to the lateral suprasylvian areas arises predominantly in layers 5 and 6 and terminates in layer 1. EVA is linked reciprocally to a thalamic zone encompassing the lateromedial‐suprageniculate complex and the adjacent medial subdivision of the latero‐posterior nucleus.

We conclude that EVA is an exclusively visual area confined to the anterior ectosylvian sulcus and bounded by nonvisual cortex. EVA is distinguished from other visual areas by its physical isolation from those areas, by its lack of consistent global retinotopic organization, and by its placement at the end of a chain of areas through which information flows outward from the primary visual cortex.
Afferent and efferent connections of the A5 noradrenergic cell group in the rat
Authors: Byrum Christopher E. , Guyenet Patrice G.
Published: January 2005

The supraspinal afferent and efferent connections of the A5 noradrenergic cell group were examined in rats. Very small deposits of HRP‐WGA were made in the rostral A5 area. Catecholamine histofluorescence techniques were used to confirm that the deposits overlapped the A5 column. Retrogradely labeled cells were present in the perifornical area and paraventricular nucleus of the hypothalamus, the Kölliker‐Fuse nucleus, dorsal parabrachial area, intermediate and caudal portions of the nucleus of the solitary tract, and the ventral medullary reticular formation in the areas of the A1 and B1 cell groups.

Anterograde HRP‐WGA labeling was found in several areas of the subcortical CNS. The contribution of A5 neurons to this labeling was confirmed with retrogradely transported fluorescent latex microspheres combined with catecholamine histofluorescence techniques. The A5 cell group was found to have significant projections to the central nucleus of the amygdala, perifornical area of the hypothalamus, midbrain periaqueductal gray, parabrachial area, and the nucleus of the solitary tract. Other A5 projections include the paraventricular nucleus of the thalamus, the bed nucleus of the stria terminalis, and possibly the zona incerta and lateral and dorsal hypothalamic areas. In addition, A5 neurons may innervate the ventrolateral reticular formation of the medulla.

Virtually all of the areas innervated by A5 noradrenergic neurons are involved in cardiovascular regulation. In addition, the A5 area receives afferent input from major cardiovascular regulatory centers of the supraspinal CNS. Thus the A5 cell group has the potential to exert a significant influence on the cardiovascular regulatory system.