bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anatomy of layer IV in cat primary auditory cortex (AI)
Authors: Winer Jeffery A. 
Published: January 2005

AbstractThe structure of neurons and axons in layer IV was studied as part of a larger inquiry into the organization of primary auditory cortex (AI) in the cat. Tissue from the convexity of the middle ectosylvian gyrus between the anterior and posterior ectosylvian sulci was studied in Golgi, Nissl, Bodian, plastic‐embedded, and other preparations from adult animals. Layer IV is defined as a strip about 200–250 μm thick consisting predominantly of small non‐pyramidal neurons intercalated between the pyramidal somata of layers III and V, and in which few commissurally projecting cells occur. Lying some 800–900 μm beneath the pia, layer IV has six types of neurons, as seen in Golgi‐stained material from anatomically and physiologically defined AI. These include three varieties (small, medium‐sized, and large) of tufted neurons with intracortically branching axons and vertically polarized, cylindrical dendritic fields. Besides the tufted cells, which are the most numerous neurons in layer IV, large multipolar, double bouquet, and spiny stellate cells are scattered through layer IV. Each has a characteristic neuronal architecture and intracortical axonal branches. Smaller tufted cell somata dominate the upper half of layer IV (IVa), larger tufted cells are more common deep in layer IV (IVb). The average somatic area in midnuclear, plastic‐embedded sections is 158 μm2. Layer IV (and layer IIIb) receive thick, probably ascending fibers, forming narrow, vertical terminal fields. These axons may be of thalamic origin and overlap with alternating, 50–75‐μm‐wide columns of somata and neuropil in layer IV. Layer III pyramidal cell axons often project to layer IV and ramify vertically and horizontally. The average height‐width ratio of the dendritic domains of layer IV cells is about 3.6:1. The vertically disposed dendrites of layer IV cells, the columnar arrangement of their local axonal branches, and the polarized form of intrinsic and extrinsic axons collectively reinforces the columnar pattern in layer IV. Many layer IV cells structurally resemble neurons in layer IV in the primary visual and somatic sensory cortex. However, most AI cells have a pronounced columnar arrangement of their somata and an elongated, narrow form. The axons of many layer IV cells preserve this vertical arrangement and often branch in layer III and, to a lesser degree, in layer V. Layer IV cells contribute little if at all to the commissural system in the primary auditory cortices, nor do they project extensively to the second auditory field adjoining AI. They might have a role in the function of local circuits within AI. Certain types of neurons appear to be common constituents in layer IV in other primary sensory cortical regions. These may represent fundamental elements of neocortical circuitry.
Distribution and morphology of nociceptive cells in the CNS of three species of leeches
Authors: Johansen Jørgen , Hockfield Susan , McKay Ronald D. G. 
Published: January 2005

AbstractThe present study describes the segmental variation in the distribution and morphology of nociceptive neurons (N cells) in the central nervous system of the leech.N cells of midbody ganglia can be segregated into lateral and medial types. We show that monoclonal antibodies specific for N cells can distinguish between the two populations. The monoclonal antibodies were used to map the complete distribution of the cells along the nervous cord. There are two pairs of medial and lateral nociceptive neurons in the midbody ganglia, one pair of the medial type in the sex ganglia (5 and 6), and a pair of the lateral type in ganglia 20 and 21. The caudal brain is without nociceptive neurons. This distribution was confirmed by electrophysiological means.The morphology of N cells in different parts of the nervous system was investigated by intracellular horseradish peroxidase (HRP) injections. In the terminal segmental ganglia the N cells showed extensive arborizations in the head and tail brains and, contrary to N cells in the midbody ganglia, their arborizations spanned more than three segments. N cells are absent in the tail brain, but the N cells of ganglia 20 and 21 were shown to innervate the entire caudal region. The basic morphology of all N‐cell homologues was found to be very similar for three leech species.In the sex ganglia the pair of N‐cell homologues were examined in Haemopis, Hirudo, and Macrobdella. The results showed a progressive modification in the three species of the cell's morphology, peripheral projections, and physiological responses, possibly correlated with the evolution and complexity of the sexual organs.HRP injections and monoclonal antibody staining revealed that a common feature of N‐cell homologues is the presence of processes that tightly surround the cell soma of other cells. This suggests that N cells may have other functional properties in addition to being primary sensory neurons.
Thalamic connections of the insula in the rhesus monkey and comments on the paralimbic connectivity of the medial pulvinar nucleus
Authors: Mufson Elliott J. , Mesulam M. Marsel 
Published: January 2005

AbstractThalamic connections of the insula in the rhesus monkey were studied with axonal transport methods. Tritiated amino acid injections limited to the insula revealed autoradiographic label in the principal and parvicellular components of the ventroposterior medial nucleus, the ventroposterior inferior nucleus, the oral and medial pulvinar nuclei, the nucleus reuniens, the parvicellular and magnocellular components of the medial dorsal nucleus, the centromedian‐parafasicularis nuclei, and the reticular nucleus.In additional animals, tritiated amino acids and horseradish perioxidase injections were made within different regions of the insula. Although the injection sites in these additional cases may have included minor extensions into claustrum and adjacent structures, several tentative conclusions emerged with respect to the antero‐posterior gradient in insulothalamic connectivity.The anterior insula appears to have a more extensive relationship with the ventroposterior medial complex, the medial dorsal nucleus, the centromedian‐parafasicularis nuclei and with some midline nuclei. In contrast, the posterior insula is more extensively connected with the ventroposterior inferior nucleus, the oral and medial pulvinar nuclei, and the suprageniculate nucleus.The patterns of insulothalamic connections support conclusions derived from observations on the cortical connectivity of the primate insular cortex indicating that the anterior insula is related to olfactory, gustatory, and viscero‐autonomic behavior, whereas the posterior insula is related to auditory‐somesthetic‐skeletomotor function (Mesulam and Mufson, '82b).The medial pulvinar nucleus has extensive connections with many paralimbic cortical regions including the insula as well as with high order polymodal association cortex. These findings suggest that the medial pulvinar may provide a region for the convergence of multisensory association input with limbic information.
Postnatal maturation of nonpyramidal neurons in the visual cortex of the cat
Authors: Meyer Gundela , Ferres‐Torres Romualdo 
Published: January 2005

AbstractA Golgi study of nonpyramidal neurons in the visual cortex of kittens aged from 1 to 80 days revealed that different neuronal types undergo a differential sequence of maturation. The earliest nonpyramidal cells to differentiate are large multipolar cells of layers 3–5, which appear around birth and whose axons gradually establish long lateral, intracortical connections. They are followed by spiny stellate cells of layer 4, which appear in the first postnatal, week, and by neuroglioform cells in layers 4 and 5, a cell type which at 10 days displays a highly differentiated axonal plexus. In general, most classes of local axon cells can be identified by the end of the second week, though still possessing a very immature morphology, the axonal‐tuft cells of layer 2 maturing later, in the third week. With some exceptions, most neurons exhibit an adultlike axonal arborization by the end of the first month; however, immature chandelier terminals are observed until the 40th day, and in kittens aged from 30 to 80 days, the vertical terminal segments of chandelier cells are larger than in the adult. Some neuronal types seem to present an exuberant growth of axonal fibers in the late postnatal period and a subsequent reduction up to the adult stage.
Cellular and connective organization of slice cultures of the rat hippocampus and fascia dentata
Authors: Zimmer J. , Gähwiler B. H. 
Published: January 2005

AbstractThis study examined the cellular and connective organization of hippocampal tissue taken from 6–8‐day‐old rats and cultured by the roller tube technique for 3–6 weeks. In the cultures containing the fascia dentata and the hippocampus proper (CA1, CA3, CA4) the main cell and neuropil layers were organotypically organized when observed in ordinary cell stains. The normal distribution of smaller cell populations of AChE‐positive neurons and somatostatin‐reactive neurons was demonstrated by histochemical and immunohistochemical methods. Both cell types were mainly confined to str. oriens of CA3 and CA1 and the dentate hilus (CA4). Individual dentate granule fells and hippocampal pyramidal cells were injected with lucifer yellow and HRP, revealing great stability of the dendritic patterns of these cells in the culture condition. The same was found for the axonal branching and termination of HRP‐filled mossy fibers arising from an HRP‐injected granule cell. The preservation of organotypic afferent patterns in the cultures was also shown by Timm staining of the terminal distribution of the mossy fiber system. Mossy fiber terminals, with characteristic ultrastructural features verified in the electron microscope, were thus found in the hilus (CA4) and along the CAS pyramidal cell layer onto the CA3‐CA1 transition. Depending on the amount of dentate tissue relative to CA3 the terminals could stop before reaching CA1 (small fascia dentata) or take up additional intra and infrapyramidal locations along CA3 (small CA3). In cultures with a gap in the CA3 pyramidal cell layer some mossy fiber terminals were found in contact with the CA3 pyramidal cells beyond the gap. In all cultures there was an aberrant projection of supragranular mossy fibers. This projection is analogous to the one known from lesion and transplant studies to form in the absence of the entorhinal perforant path input to the dentate molecular layer. Also, in accordance with these studies the Timm staining pattern of the outer parts of the dentate molecular layer and the entire molecular layer of the hippocampus was altered corresponding to the spread of afferents normally confined to the inner zone of the dentate and str. radiatum of CA3 and CA1. Possibly as a consequence of the lack of normal targets for projections from CA1, this subfield contained an unusually dense Timm staining suggestive of autoinnervation.In the analysis of the cellular and connective organization of hippocampal slice cultures both normal and additional traits were found. The normal traits demonstrated the stability of the intrinsic structure once it survives in vitro. The additional traits had formed according to the principles for reorganization of nerve connections known from lesion and transplant studies of hippocampal and dentate tissue.
Quantitative studies of auditory hair cells and nerves in lizards
Authors: Miller Malcolm R. 
Published: January 2005

AbstractBecause the lizard cochlear duct is anatomically accessible as well as relatively simple in structure it is an excellent model in which to study auditory hair cells, nerve fibers, and innervational patterns. The objectives of this study were to determine the intra‐ and interspecific variations of auditory hair cell and nerve fiber numbers, nerve fiber/hair cell ratios, and nerve fiber sizes in a variety of lizard species and to relate these to auditory function and phylogeny.Hair cell numbers were determined by SEM and serial frontal sections of the papilla basilaris and nerve fiber numbers and diameters by use of a Zeiss TGZ3 particle counter. The coefficient of variation of hair cell numbers varied from 3.2 to 16.6 (171 specimens, 15 species) and of nerve fiber numbers from 1.2 to 14.4 (381 specimens, 35 species). There was no correlation between hair cell or nerve fiber number and age or sex.The nerve fiber number/hair cell number ratio was 3.5–11.1/1 in small papillae basilares of the iguanid‐agamid‐anguid type, 2.4–3.2/1 in the teiid type, and 0.6–1.5/1 in the larger specialized papillae of the scincid and gekkonid types.Nerve fibers varied in diameter from 0.8 to 6.0 μm (largest percentage were 2–4 μm) and were unimodally distributed. Larger nerve fibers usually supplied the unidirectionally oriented hair cells of the papilla basilaris.Variations in hair cell and nerve fiber numbers in other vertebrate classes and the functional and phylogenetic aspects of lizard papilla basilaris structure and innervation are discussed.
T reticular interneurons: A class of serially repeating cells in the zebrafish hindbrain
Authors: Kimmel Charles B. , Metcalfe Walter K. , Schabtach Eric 
Published: January 2005

AbstractWe describe a class of reticular neurons, named T interneurons after the branching pattern of their axons, in young larvae of the zebrafish Brachydanio rerio. The cells were identified by filling them with HRP from application sites within the CNS. A serially repeating set of about ten such neurons is present in a longitudinal column on each side of the caudal hindbrain. The T axons project across the midline, and branches course both rostrally and caudally within the medial longitudinal fascicle (mlf). The cells receive synaptic input from the Mauthner neurons, from unidentified axons in the mlf, and perhaps from trigeminal sensory fibers. They project to cranial and pectoral motor nuclei.T interneurons appear to be homologous to giant fiber neurons in the hatchetfish and to some of the cranial relay neurons in the goldfish. We discuss a possible functional role and comparative implications of their distribution in the hindbrain.
Organization of the rostral thalamus in the rat: Evidence for connections to layer I of visual cortex
Authors: Rieck Richard W. , Carey Russell G. 
Published: January 2005

AbstractThe present study demonstrates the organization of a thalamocortical projecting system which terminates within layer I of the visual cortex in the hooded rat. Horseradish peroxidase (HRP) injections restricted to layer I resulted in retrograde labeling of large and medium‐sized multipolar and fusiform neurons that are located within the ventromedial (VM) nucleus and a dorsomedial subunit of the ventral anterolateral nucleus (VAL). Retrograde cellular labeling also occurs within the anteromedial nucleus (AM) following these injections. After restriction of HRP injections to layer I, peroxidase labeling was not found within neurons of the classically defined intralaminar system, i.e., central medial, paracentral, and central lateral nuclei, or within the rostral continuations of the intralaminar system. Since the VM, dorsomedial VAL, and AM nuclei are directly adjacent to portions of the internal medullary lamina, we refer to this amalgam of rostral thalamic nuclei that project to layer I as the “paralaminar” system. We also provide cytoarchitectonic criteria that can be used to distinguish three separate subdivisions within the VAL complex, including that portion of the VAL which is part of the “paralaminar” system. In contrast, when control injections of WGA‐HRP are placed within either the cellular supragranular or infragranular layers of the visual cortex, no appreciable number of neurons are labeled within the VM, VAL, or AM.
Afferent connections of gudden's tegmental nuclei in the rabbit
Authors: Hayakawa Tetsu , Zyo Katuya 
Published: January 2005

AbstractThe regions projecting to Gudden's tegmental nuclei were examined by retrograde transport of horseradish peroxidase or wheat‐germ‐agglutinin‐conjugated horseradish peroxidase. Gudden's tegmental nuclei in the rabbit can be divided into a pars principalis of the ventral tegmental nucleus (TVP), a pars ventralis of the dorsal tegmental nucleus (TDV), and a pars dorsalis of the dorsal tegmental nucleus (TDD).The TVP receives many fibers from the medial division of the ipsilateral medial mammillary nucleus and bilaterally from the lateral habenular nucleus, and additionally some fibers from the posterior nucleus of the interpeduncular complex. The TDV receives many fibers from the ipsilateral lateral mammillary nucleus, from the ipsilateral prepositus hypoglossi nucleus, bilaterally from the lateral habenular nucleus, from the central and paramedian nuclei of the interpeduncular complex, from the bilateral gray matter along the floor of the fourth ventricle, and from the contralateral supragenual nucleus. The TDD receives a projection from the lateral habenular nucleus of both sides and from the central and paramedian nuclei of the interpeduncular complex, and a minor projection from the ipsilateral lateral mammillary nucleus, the posterior nucleus of the interpeduncular complex, the prepositus hypoglossi nucleus, and the contralateral supragenual nucleus.
Trigeminocerebellar, trigeminotectal, and trigeminothalamic projections: A double retrograde axonal tracing study in the mouse
Authors: Steindler Dennis A. 
Published: January 2005

AbstractDouble retrograde axonal tracing experiments were carried out in order to reveal potential patterns of divergence in axonal projections from the two major sensory nuclei of the mouse brainstem trigeminal complex: the principal sensory and spinal trigeminal nuclei (oralis, interpolaris, and caudalis divisions). The tracers wheat germ agglutinin, N‐[acetyl‐3H] and horseradish peroxidase were used in paired injection strategies within portions of the cerebellum, superior colliculus, and thalamic ventrobasal complex and/or posterior group of adult ICR white mice.Trigeminal neurons with projections to tactile areas of the cerebellar cortex or underlying deep cerebellar nuclei were found scattered throughout the principal sensory nucleus and interpolaris division, and mainly in dorsal regions of the oralis division of the spinal trigeminal nucleus. Injections of either tracer which involved lateral portions of the rostral half of the superior colliculus labeled trigeminotectal neurons mainly in the contralateral interpolaris division, ventral half of the oralis division, and a ventral region of the principal sensory nucleus near the oralis border. Fewer trigeminotectal neurons were found scattered throughout the principal sensory nucleus and the magnocellular layer of the caudalis divisions, although an occasional labeled neuron was also found in the marginal layer. Contralaterally projecting trigeminothalamic neurons were observed throughout the principal sensory nucleus, interpolaris division, and within the marginal and magnocellular layers of caudalis.Double‐labeled neurons were observed only after paired injections of the tracers in the thalamus and ipsilateral superior colliculus, and they were found within the caudoventral portion of the principal sensory nucleus near the oralis border, throughout the interpolaris division, within the magnocellular layer of caudalis, and only a few double‐labeled neurons were also found within the marginal layer. After such injections. 50% of the labeled tectum‐projecting neurons in the principal sensory nucleus, 64% in the interpolaris division, and 57% in the caudalis division are branched neurons which have collateralized projections to both the superior colliculus and thalamus. These projections, which have not been described before, appear to arise from more than one class of projection neuron which is differentially distributed within different regions of the trigeminus.
Corticothalamic connections of the posterior parietal cortex in the rhesus monkey
Authors: Yeterian Edward H. , Pandya Deepak N. 
Published: January 2005

AbstractCorticothalamic connections of posterior parietal regions were studied in the rhesus monkey by using the autoradiographic technique. Our observations indicate that the rostral superior parietal lobule (SPL) is connected with the ventroposterolateral (VPL) thalamic nucleus. In addition, whereas the rostral SPL is connected with the ventrolateral (VL) and lateral posterior (LP) thalamic nuclei, the rostral IPL has connections with the ventroposteroinferior (VPI), ventroposteromedial parvicellular (VPMpc), and suprageniculate (SG) nuclei as well as the VL nucleus. The caudal SPL and the midportion of IPL show projections mainly to the lateral posterior (LP) and oral pulvinar (PO) nuclei, respectively. These areas also have minor projections to the medial pulvinar (PM) nucleus. Finally, the medial SPL and the caudal IPL project heavily to the PM nucleus, dorsally and ventrally, respectively. In addition, the medial SPL has some connections with the LP nucleus, whereas the caudal IPL has projections to the lateral dorsal (LD) nucleus. Furthermore, the caudal and medial SPL and the caudal IPL regions have additional projections to the reticular and intralaminar nuclei–the caudal SPL predominantly to the reticular, and the caudal IPL mainly to the intralaminar nuclei.These results indicate that the rostral‐to‐caudal flow of cortical connectivity within the superior and inferior parietal lobules is paralleled by a rostral‐to‐caudal progression of thalamic connectivity. That is, rostral parietal association cortices project primarily to modality‐specific thalamic nuclei, whereas more caudal regions project most strongly to associative thalamic nuclei.
Large neurons in the primate neostriatum examined with the combined Golgi‐electron microscopic method
Authors: DiFiglia Marian , Carey Janice 
Published: January 2005

AbstractLarge neurons in the monkey neostriatum were examined in the electron microscope in tissue treated with the rapid‐Golgi impregnation method followed by the gold‐toning procedure. Two types of large neurons were investigated: an aspiny neuron (aspiny type II; N = 5) with numerous varicose dendrites and a spiny cell (spiny type II; N = 1) with few sparsely spined dendrites. The large aspiny neurons had variably shaped somata, an eccentric highly invaginated nucleus, and a cytoplasm rich in organelles. Mitochondria were distributed unevenly in dendrites and were localized primarily in varicosities. Some mitochondria exhibited dense hodies 80–300 nm in size. Most synapses (84%) onto large aspiny neurons occurred 20 μm or more from the cell body and contacted dendritic varicosities (63%). A smaller proportion of boutons (21%) contacted constricted portions of varicose segments. A low incidence of synaptic boutons was observed on smooth primary and secondary dendrites (11%), cell bodies (3%), and branch points (2%). Seven percent of the axons that synapsed with large aspiny neurons also contacted nearby dendrites or spines of medium‐sized spiny neurons. At least eight morphologically distinct types of axons making synapses with large aspiny neurons were identified and included both symmetric and asymmetric types.The large spiny neuron was different from the large aspiny neuron in its subcellular characteristics. Synapses were found on all portions of the cell, including the axon initial segment, but fewer types of axonal inputs were identified.These findings confirm that the two types of large neurons identified in Golgi impregnations of the primate neostriatum are also different at the ultrastructural level, both in their cytological features and in their synaptic organization. The large aspiny neuron integrates synaptic inputs that innervate a relatively large area of caudate neuropil and appear to arise from a variety of extrinsic and intrinsic sources. The high density of synaptic inputs to dendritic varicosities suggests that they have an important functional role.