bluuebunny/crossref_metadata_2025 huggingface dataset:
Occipital cortex in man: Organization of callosal connections, related myelo‐ and cytoarchitecture, and putative boundaries of functional visual areas
Authors: Clarke Stephanie , Miklossy Judit
Published: January 2005

Human area 17 is known to contain a single (the primary) visual area, whereas areas 18 and 19 are believed to contain multiple visual areas (defined as individual representations of the contralateral visual hemifield). This is known to be the case in monkeys, where several boundaries between visual areas are characterized by bands of callosal afferents and/or by changes in myeloarchitecture. We here describe the pattern of callosal afferents in (human) areas 17, 18, and 19 as well as their cortical architecture and we infer the position of some visual areas.

Sections from occipital lobes of 6 human brains with unilateral occipital infarctions have been silver‐impregnated for degenerating axons, thereby revealing callosal afferents to the intact occipital cortex. Their tangential distribution is discontinuous, even in cases with large lesions. A band of callosal afferents straddles the area 17/18 boundary, whereas the remainder of area 17 and a 15–45 mm wide stripe of area 18 adjacent to the callosal band along the 17/18 border are free of them. Patches of callosal afferents alternate with callosal‐free regions more laterally in area 18 and in area 19. We conclude that, in man, a second visual area (analogue of V2) lies in area 18, horseshoe‐shaped around area 17, and includes the inner part of the acallosal stripe adjacent to the callosal band along the 17/18 boundary. The outer part of this acallosal stripe belongs to a third visual area, which may contain dorsally the analogue of V3 and ventrally that of VP. Thus the lower parts of the second and third visual areas lie on the lingual gyrus, whereas the analogue of the macaque's fourth visual area probably lies on the fusiform gyrus.

Although the proposed subdivision of the occipital cortex relies largely on the pattern of callosal afferents, some putative human visual areas appear to have distinct architectonic features. The analogue of V2 is rather heavily myelinated and its layer III contains large pyramidal neurons. Its upper part is not well delimited laterally since adjacent “V3” has similar architecture. Its lower part, however, differs clearly from the adjacent “VP,” which is lightly myelinated and lacks the large pyramids in layer III. The cortex lateral to “VP” is heavily myelinated and contains fairly large pyramids in layers III and V. The myeloarchitecture of the lateral part of the occipital cortex is not uniform; a very heavily myelinated region stands out in the lateral part of area 19, near the occipito‐temporal junction. This region is likely to be the analogue of the macaque's area V5‐MT.
Catecholaminergic innervation of the hippocampus in the cynomolgus monkey
Authors: Samson Yves , Wu Justin J. , Friedman Allan H. , Davis James N.
Published: January 2005

We studied the immunocytochemical distribution of catecholaminergic fibers in the hippocampal formation from two cynomolgus monkeys by using phenylethanolamine‐N‐methyltransferase, dopamine‐beta‐hydroxylase, and tyrosine‐hydroxylase antibodies. There were no phenylethanolamine‐N‐methyltransferase immunoreactive fibers suggesting the lack of epinephrine containing fibers. In order to compare the distributions of tyrosine‐hydroxylase and dopamine‐beta‐hydroxylase immunoreactive fibers, we counted fibers in four hippocampal regions, the dentate gyrus, CA3, CA1, and the subiculum at three different rostrocaudal levels. The distributions of dopamine‐beta‐hydroxylase and tyrosine‐hydroxylase immunoreactive fibers were overlapping but clearly different, suggesting that the hippocampus receives both noradrenergic and dopaminergic inputs in primates. Dopamine‐beta‐hydroxylase‐immunoreactive fibers were present in moderate density and roughly evenly distributed throughout the hippocampus. Tyrosine‐hydroxylase immunoreactive fibers were found in high density in the dentate gyrus, in the stratum lacunosum‐moleculare, and in the molecular layer of the subiculum. There were only minor side‐side and rostrocaudal differences in the distribution of tyrosine‐hydroxylase and dopamine‐beta‐hydroxylase immunoreactive fibers. The identification of a putative dopaminergic projection to primate hippocampus, which is more dense and widely distributed than in the rodent, parallels similar increases in dopaminergic projections reported for primate cerebral neocortex.
Galanin immunoreactive neurons in the human hypothalamus: Colocalization with vasopressin‐containing neurons
Authors: Gai W. P. , Geffen L. B. , Blessing W. W.
Published: January 2005

Galanin (GA) is a recently described neuropeptide that has been demonstrated to be widely distributed in the hypothalamus of experimental animals. So far there is no immunohistochemical description of GA in the human hypothalamus and, in particular, no studies of the colocalisation of this neuropeptide with other transmitter candidates in the human hypothalamus. We have now investigated this question immunohistochemically by using human brains fixed by vascular perfusion within 24 hours of death. Nerve cell bodies and fibers stained for GA were observed throughout the hypothalamus. Major populations of GA‐ir cell bodies were found in the suprachiasmatic, intermediate, supraoptic, para ventricular, arcuate, tuberomammillary, and supramammillary nuclei. Scattered positive neurons were found in the periventricular preoptic area, the posterior hypothalamic nucleus, the lateral hypothalamic area, and zona incerta. A few positive cells were located in the dorsomedial and ventromedial hypothalamic nuclei. The number of GA‐ir neurons estimated from three brains was 11,100 ± 2,400 for the intermediate nucleus, 57,800 ± 9,100 for the supraoptic nucleus and 47,400 ± 13,900 for the para ventricular nucleus. GA‐ir fibers were widely distributed in the hypothalamus. They were more dense in the periventricular and medial hypothalamic zones, whereas the lateral tuberal nuclei and the dorsolateral part of the supraoptic nucleus contained sparse positive fibers. The mammillary complex contained almost no GA‐ir fibers. In the ventromedial tuberal region, GA‐ir axons formed bundles travelling down in the infundibular stem. In the median eminence the vascular plexus was wrapped by GA‐ir fiber networks.

The coexistence of GA with arginine vasopressin (AVP), oxytocin (OXY), and tyrosine hydroxylase (TH) was examined in the supraoptic, paraventricular, and suprachiasmatic nuclei in adjacent paraffin sections. Neurons containing both GA and AVP were very common in the supraoptic nucleus and also occurred in the paraventricular and suprachiasmatic nuclei. The supraoptic and paraventricular nuclei also contained some neurons immunoreactive for both GA and OXY. Neurons positive for GA and TH were rare.

The topographic distribution of GA‐ir neuronal structures in the hypothalamus and the colocalization of GA, principally with AVP and to a lesser extent with OXY, in some hypothalamic nuclei constitute anatomical evidence that this neuropeptide may be involved in the regulation of endocrine, autonomic, and behavioural homeostatic responses.
The projection from different visual cortical areas to the rat superior colliculus
Authors: Harvey Alan R. , Worthington Delys R.
Published: January 2005

The rat occipital cortex contains a number of morphologically and physiologically distinct visual areas. Retrograde tracing studies have shown that most if not all of these areas project in a topographic fashion to the ipsilateral superior colliculus (SC). In the present study, small amounts of wheat germ agglutinin‐conjugated HRP (WGA‐HRP) were injected into adult rat occipital cortex to determine how afferents from the different visual cortical areas are distributed within the various layers of the SC. Cytoarchitectonic criteria were used to help establish the location of the WGA‐HRP injections in the cortex. As a further aid to identifying the sites of injection, the distribution of retrogradely labelled cells within the thalamus was mapped in each brain.

Analysis revealed a surprising range of visuocortical projections to the rat SC, with input to the majority of tectal laminae. Area 17 projected most heavily to the dorsal stratum opticum (SO) and lower half of stratum griseum superficial (SGS) with lighter label extending up to the collicular surface, Axons and terminals from area 18 formed two horizontal tiers, one in the middle of the stratum griseum intermediale (SGI) and the other at the border between the stratum album intermediale (SAI) and the stratum griseum profundum (SGP). Periodic puffs of label extended between these horizontal tiers, with a periodicity of 300–400 μm. There was some variability in the labelling pattern in the superior colliculus after area 18a injections, perhaps because this cytoarchitectonic area contains multiple representations of the visual field. Generally the projection from the lateromedial, laterointermediate, and laterolateral parts of 18a was heaviest in the lower half of SO and upper regions of SGI. Lighter label extended up into the lower half of SGS. In the SGI it was common to find periodic puffs of terminal label interspersed with areas devoid of innervation. This periodic pattern was particularly noticeable after WGA‐HRP injections into anterior 18a. Two horizontal tiers of label were located at the SO/SGI border and SGI/SAI border (the dorsal being the most dense) with patches of label extending between these tiers every 230–250 μm. There did not appear to be a significant corticotectal projection from the posterior part of the lateral extrastriate region.
Thalamic projections to sensorimotor cortex in the newborn macaque
Authors: Darian‐Smith Corinna , Darian‐Smith Ian , Cheema Surindar S.
Published: January 2005

In the present experiments thalamocortical projections to different functional areas of the newborn (or prematurely delivered) macaque's sensorimotor cortex were labeled using retrogradely transported fluorescent dyes. Several dyes were used in each animal to (1) enable the direct comparison of the soma distributions of different thalamocortical projections within thalamic space, and (2) identify by double labeling neurons shared between these distributions. The projection patterns in the newborn macaque were compared with those of the mature animal reported by Darian‐Smith et al. (J. Comp. Neurol. 1990;298:000–000).

The main observations were (1) all thalamocortical projections to the sensorimotor cortex of the mature macaque are well established by embryonic days 146–150, as was shown by labeling these pathways in infants delivered by cesarian section, (2) a significant number of thalamocortical neurons in the newborn were double‐labeled following dye injections into different pre‐ or postcentral areas, and where the margins of the dye uptake zones were separated by 3–8 mm, and (3) extensive projections from the anterior pulvinar nucleus to the motor and premotor cortex, and to the supplementary motor cortex were labeled in the newborn macaque. Both the exuberant terminal arborizations, and the precentral pulvinar projections were diminished by the 6th postnatal month, and absent in the mature macaque. The role of epigenetic determinants of these postnatal events is briefly considered.
Lateral magnocellular thalamic nucleus in rabbits: Architecture and projections to cingulate cortex
Authors: Vogt Brent A. , Sikes Robert W.
Published: January 2005

The lateral magnocellular nucleus (LM) contains the largest neurons in the rabbit thalamus, yet its cortical connections have not been described. This study evaluates the architecture, cingulate cortical connections, and spontaneous rate of neuronal discharges in LM. At its maximal mediolateral extent in coronal sections, LM underlies the laterodorsal and lateroposterior nuclei. It has a short medial and long lateral limb, both of which have high levels of cytochrome oxidase activity. On the basis of horseradish peroxidase and fluorescent dye injections, LM projects primarily to area 29 and posterior area 24. Projections to area 29d are topographically organized so that the medial limb of LM projects to rostral area 29d, mid levels of LM where the limbs join project to midlevels of area 29d and lateral parts of the lateral limb project to posterior area 29d. It is mainly the midportion of the lateral and medial limbs that projects to areas 29b and 29c. The anterior parts of these areas receive input from dorsal parts of LM, whereas posterior levels of these areas receive input from ventral LM. The midregion of LM also projects to caudal area 24. Injections of 3H‐amino acids into area 29d anterogradely label neuronal processes in LM. Finally, single unit electrophysiological recordings from LM in halothane‐anesthetized rabbits showed a unique pattern of spontaneous discharges. Over 70% of the LM neurons cycled through a number of different phases with a mean ± S.E.M. peak discharge rate of 31 ± 4.7 Hz. This high rate contrasts with the 17.6 ± 3.2 Hz rate for neurons that maintained a constant rate of discharge and the 7.5 ± 1.3 Hz rate of discharges for neurons in nuclei dorsal and ventral to LM.

LM neurons are large, have high levels of cytochrome oxidase and spontaneous activity, and project extensively to the posterior cingulate cortex. These features suggest that LM neurons are highly active metabolically and may be fast conducting efferents to cingulate cortex.
Three‐dimensional structural organization of layer I of the human cerebral cortex: A golgi study
Authors: Marín‐Padilla Miguel
Published: January 2005

The three‐dimensional structural organization of layer I of the developing and adult human cerebral cortex has been investigated by using sagittal, transverse, and tangential rapid Golgi and Klüver‐Barrera preparations. The actual morphology of its fundamental neuron—the Cajal‐Retzius cell (C‐R)—is established. These large and solitary cells are horizontal multipolar neurons characterized by: (1) long horizontal dendrites that radiate in all directions within a tangential plane parallel to the pial surface, (2) long horizontal axonic collaterals that radiate in all directions within layer I middle level, and (3) a descending axonic process that reaches the lower level, becomes a long tangential fiber—and eventually a myelinated one—and projects in any direction within this level. In cortical ontogenesis, its dendrites, axonic collaterals and terminal axon undergo a progressive multipolar “horizontalization” extending throughout the surface of the expanding cerebral cortex. The neuron's body and main dendrites will be found only in some areas, whereas its axonic collaterals and terminal tangential axon should be found throughout the cerebral cortex. This developmental feature explains the presence of two—middle and lower—plexuses in layer I, composed of the axonic collaterals and the terminal tangential axons of C‐R cells, respectively. It is emphasized that the basic morphology of the C‐R cell remains essentially unchanged in the course of cortical ontogenesis and that the neuron persists in the adult cerebral cortex. Whereas the C‐R cell is the basic neuron of layer I, the pyramidal cells dendritic bouquets represent its larger and main receptive surface (the only one early in development). By the 30th week of gestation, a C‐R cell could establish: (1) proximal contacts, through its axonic collaterals, with all dendritic bouquets within a ∼ 350 μm radius, and (2) distant contacts, through its tangential axon, with dendritic bouquets within a narrow sagittal, transverse, or diagonal territory several mm long. In cortical ontogenesis, the C‐R cells' functional territories continue to expand throughout the surface of the cerebral cortex and possibly overlap with each other, It is proposed that the C‐R cell receives inputs from primitive (mesencephalic?) corticipetal fibers and that it transmits the same kind of information (perhaps a basal tone?) to the dendritic bouquets of all pyramidal neurons throughout the cerebral cortex regardless of their location, cortical depth, or functional role.
Morphological variability, segmental relationships, and functional role of a class of commissural interneurons in the spinal cord of goldfish
Authors: Fetcho Joseph R.
Published: January 2005

As part of an attempt to understand the spinal control of the segmented axial musculature in goldfish, commissural spinal interneurons that are electrotonically coupled to the Mauthner axon (M‐axon) were studied with intracellular recording and staining to examine their morphology, segmental relationships, and functional role. Prior studies suggested that these cells might mediate the crossed inhibition that blocks excitation of motoneurons on one side of the body during an escape bend to the opposite side. Simultaneous intracellular recordings from a M‐axon, a commissural interneuron coupled to it, and a presumed primary motoneuron show that: (1) the interneurons produce monosynaptic, CI−‐dependent IPSPs in contralateral motoneurons, (2) the interneurons are responsible for the short latency, crossed spinal inhibition in the M‐cell network, and (3) more than one interneuron terminates on each postsynaptic cell. Reconstructions of interneurons from wholemounts show that they form a fairly homogeneous morphological class of cells. Each one is unipolar, with an axon that crosses the cord and then usually bifurcates into a short, thin ascending branch and a thicker, longer descending one. Neighboring interneurons have overlapping terminal arbors consistent with the physiological data showing convergence of interneurons onto the same postsynaptic cell. The interneurons showed little relationship with body segments as denned by ventral roots. Their axons usually straddled segmental boundaries, with terminals typically occupying parts of two adjacent segments. Thus the functional unit of these cells is probably not a segment or a complete group of segments, but instead includes only parts of two adjacent segments. The presence of interneurons like these suggests that the overt peripheral segmentation of trunk musculature is not necessarily reflected in the organization of neurons that control those segments. A consideration of some functional characteristics of the activation of overlapping, serially repeated arrays of interneurons by descending pathways leads to the conclusion that the high conduction velocity of the M‐axon, and the large size and short longitudinal extent of the axons of the inhibitory interneurons promote a strong, brief inhibition that is appropriate for the production of an escape turn that has a rapid bend to one side.
Ultrastructure of the electrotonic and chemical components of the lateral‐to‐motor and medial‐to‐motor synapses in crayfish nerve cord
Authors: Bosch Elizabeth
Published: January 2005

Lateral‐to‐motor and medial‐to‐motor synapses in crayfish nerve cords are composed of an electrical and a chemical component. The presynaptic terminals showed localized clusters of synaptic vesicles, electron‐dense areas, coated pits, and coated vesicles. In thin sections, active zones were defined by electron‐dense regions where synaptic vesicles attached and, in freeze‐fracture replicas, by clusters of intramembrane particles localized in bands with vesicle openings on the sides of these bands.

The cytoplasmic surface of the postsynaptic membrane opposite the active zones was coated with electron‐dense material that in freeze‐fracture replicas was seen as an increase in intramembrane particles located in the external leaflet (EF‐face). This specialization of the postsynaptic membrane may correspond to the neurochemical receptor. Also, pre‐ and postsynaptic membranes were separated by a wider extracellular gap than those of adjacent nonsynaptic regions and electrical synapses or gap junctions.

Synaptic vesicles were located exclusively at the synaptic regions by means of a cytoskeleton that was different for the electrical and the chemical components. The vesicles associated with the electrical component were anchored to a cytoskeleton composed of a beaded layer of densities located parallel to the membrane. This cytoskeleton maintained the synaptic vesicles separated from the presynaptic membrane by a distance of 13 ± 2 nm. The synaptic vesicles associated with the chemical component were anchored to electron‐dense regions formed by filaments arranged in bundles, anchored to the presynaptic membrane. Vesicles lined both sides of the bundle of filaments in very close proximity to the presynaptic membrane, probably positioned to discharge their contents into the extracellular space and to replace the discharged vesicles.
Cochlear innervation in the developing rat: An immunocytochemical study of neurofilament and spectrin proteins
Authors: Hafidi A. , Despres G. , Romand R.
Published: January 2005

We have studied the innervation of the developing cochlea by immunocytochemical staining of the cytoskeletal proteins, neurofilament (NF), and spectrin (brain spectrin and erythrocyte spectrin). NF immunoreactivity was seen in spiral ganglion cell bodies and their processes and in fibers of the intraganglionic spiral bundle (IGSB) on gestational day 16. NF immunoreactivity with monoclonal antibodies to NF160 and NF68 was present beneath both inner hair cells (the IHC) and outer hair cells (OHCs) on gestational day 20. NF200 immunostaining was located only in the IGSB and in fibers reaching the IHC, The first NF200 immunoreactivity beneath the OHCs was seen in the basal turn at birth, NF labelling began to decrease on postnatal day 9 and its intensity became more like that of the adult. Brain spectrin immunostaining was first seen in the IGSB of the basal turn on gestational day 18. It reached the fibers between the spiral ganglion and the IHC on gestational day 20. Brain spectrin immunoreactivity was first seen beneath the OHCs in the basal turn at birth. It reached all the OHCs of the cochlea by postnatal day 4, and began to decrease 9 days after birth. Erythrocyte spectrin immunostaining was first observed during the second postnatal week, when it labelled spiral ganglion cells. The distribution of NF200 and brain spectrin immunoreactivity suggested that efferent innervation of OHCs is present at birth in the rat, and confirms previous studies showing the early efferent innervation of the OHCs of the mouse and the rat at birth, and the time lag between the appearance of the two spectrin isoforms during development.
Synaptic connections of neuropeptide Y (NPY) immunoreactive neurons in the hilar area of the rat hippocampus
Authors: Deller Thomas , Leranth Csaba
Published: January 2005

Synaptic connections and fine structural characteristics of neuropeptide Y‐immunoreactive (NPY‐i) neurons in the fascia dentata were studied using an antiserum against NPY. Normal and colchicine pretreated rats were examined to study the synaptic connections of NPY‐i neurons in the normal fascia dentata. The perforant pathway and fimbria fornix were transected to label afferent fibers to NPY‐positive cells. Horseradish peroxidase conjugated with wheat germ agglutinin (HRP‐WGA) was injected into the contralateral hippocampus to study commissural projections of hippocampal NPY‐i neurons, and to search for NPY‐i synaptic contacts on immunonegative commissural cells. Since earlier reports have shown that at least half of the NPY‐i neurons also contain somatostatin (SS), the distribution of NPY‐i neurons in the hilar area was determined and compared with that of SS‐i neurons. Four types of dentate NPY‐i neurons were distinguished: Type 1: large multipolar cells in the deep hilus (9%). Type 2: medium‐sized multipolar and fusiform hilar neurons with dendrites occasionally reaching the outer molecular layer (64%). Type 3: pyramidal shaped cells in the granule cell layer with long apical dendrites reaching the outer molecular layer (20%), Type 4: small multipolar NPY‐i cells located in the molecular layer (7%). Our results indicate two overlapping but not identical cell populations of NPY‐i and SS‐i neurons. Light and electron microscopic analysis of the normal fascia dentata demonstrated that the majority of NPY‐i terminals are located in the outer molecular layer of the dentate gyrus, where they establish symmetric synaptic contacts on dendritic shafts and occasionally on spines of granule cells. A moderate number of NPY‐i synapses were also found on dendrites in the inner molecular layer and on the cell body of granule cells. Numerous symmetric NPY‐i synapses were found on dendrites and somata of neurons in the hilar area. Some NPY‐i dendrites in the hilar area received mossy axon collateral input. After transection of the perforant pathway degenerated axon terminals could be found in synaptic contact with NPY‐i dendrites in the outer molecular layer. Commissurotomy revealed direct commissural input to NPY‐i dendrites in the inner molecular layer and in the hilus. After injection of HRP‐WGA into the contralateral hippocampus 2% of hilar NPY‐i neurons were retrogradely labeled and symmetric NPY‐i synapses were found on the cell bodies and dendrites of unstained HRP‐WGA labeled neurons. This study suggests that NPY‐i neurons receive entorhinal and commissural afferents and in turn form contacts with granule cells and commissural neurons in the fascia dentata. Some NPY‐i neurons may be the targets of perforant pathway afferents as well as mossy axon collaterals which may explain their vulnerability to hippocampal seizure activity.
Collaterals from lateral and medial olivocochhlear efferent neurons innervate different regions of the cochlear nucleus and adjacent brainstem
Authors: Ryan Allen F. , Keithley Elizabeth M. , Wang Zhi‐Xian , Schwartz Ilsa R.
Published: January 2005

Two populations of superior olivary neurons which project to different sensory cell regions in the cochlea also give off collateral projections to the ventral cochlear nucleus (VCN) and adjacent brainstem. To determine whether these VCN projections also have different targets, they were characterized by selective retrograde amino acid transport. Retrograde transport of 3H‐d‐aspartate (D‐ASP) selectively labeled the unmyelinated fibers and neurons of the lateral olivocochlear (OC) system, including a dense collateral projection to the central VCN. Retrograde transport of 3H‐nipecotic acid (NIP) labeled the myelinated fibers and neurons of the medial OC system, including collateral projections to the peripheral VCN, subpeduncular granule cells, and nucleus Y. Medial and lateral OC efferent collaterals thus innervate different regions of the CN. Lateral system collaterals overlap extensively with Type I spiral ganglion cell afferent input. They are well positioned to play a role in modulating afferent input to the central auditory system, as is the primary projection of these efferents to the cochlea. The medial system collaterals project near the recently described afferent projections of Type I1 spiral ganglion cells. The medial system collaterals may therefore be related to the function of outer hair cells, as the medial system primary axons appear to be in the cochlea.
Effects of visual or light deprivation on the morphology, and the elimination of the transient features during development, of type I retinal ganglion cells in hamsters
Authors: Lau Kam Chetjng , So Wok‐Fai , Tay David
Published: January 2005

Intracellular injection of Lucifer Yellow (LY) was used to study the detailed morphology of the normal, visually deprived, and light‐deprived superior colliculus projecting Type I retinal ganglion cells (RGCs) in hamsters. The soma size of the normal Type I cells ranged from 337 to 583 pm2 with a mean of 436 pm2. Two to six primary dendrites were observed in these cells. The mean dendritic field diameter was 495 km and ranged from 309 to 702 pm. The dendritic field diameter of this population of cells exhibited an eccentricity dependence. Quantitative comparisons between the normal and visually deprived or light‐deprived Type I RGCs indicated that the morphology of these three groups of cells were similar to each other in terms of the soma size, dendritic field diameter, branching pattern, and total length of the dendrites.

During the normal development of cats and hamsters, several transient features, such as exuberant dendritic spines and intraretinal axonal branches, have been observed in the developing RGCs. The complete elimination of these transient features occurs at about 3 and 2 weeks after the opening of the eyes in cats and hamsters, respectively. In the present study, the hypothesis whether visual experience or light stimulation is required for the elimination of these transient features during development was examined. After studying a total of 115 mature Type I RGCs, which included cells from the normal, visually deprived, and light deprived animals, no transient feature was observed.

We conclude that visual or light deprivation has no effect on the morphological develop‐ ment of superior colliculus projecting Type I RGCs in hamsters, and the elimination of the transient features on the Type I RGCs during development does not depend on visual experience or light stimulation.
A vasopressin and oxytocin containing nucleus in the pig hypothalamus that shows neuronal changes during puberty
Authors: van Eerdenburg Frank J. C. M. , Poot Peter , Molenaar Gerard J. , van Leeuwen Fred W. , Swaab Dick F.
Published: January 2005

A vasopressin and oxytocin containing nucleus is described for the first time in the pig hypothalamus. It is located near the third ventricle, just dorsal to the suprachiasmatic nucleus, and consists of magnocellular neurons, similar to those of the supraoptic nucleus and paraventricular nucleus. Morphometric analysis of neuronal number, size, density, and volume was performed at four different ages: 1 day, 7 weeks, 16 weeks, and 30 weeks postnatally. No sex difference in these parameters was observed. In this period the volume of the nucleus increased gradually from 6.6 X 10−3 to 54.2 X 10−3 mm3. One day after birth 1,215 ± 191 (mean ± SEM) neurons were present in the vasopressin and oxytocin containing nucleus, followed by a decrease to 771 ± 80 neurons at 7 weeks and 697 ± 116 at 16 weeks. Between 16 and 30 weeks (puberty) there was a dramatic increase in neuron number up to 1,765 ± 214 neurons. This increase in the number of vasopressin and oxytocin containing neurons in the pig hypothalamus is much later in development than has ever been reported so far.
The anterior ectosylvian sulcal auditory field in the cat: I. An electrophysiological study of its relationship to surrounding auditory cortical fields
Authors: Clarey Janine C. , Irvine Dexter R. F.
Published: January 2005

The extent of a region containing acoustically responsive neurons within the anterior ectosylvian sulcus and its relationship to surrounding gyral auditory cortical fields was examined in chloralose‐anaesthetized cats. Multiple microelectrode penetrations were made orthogonal to the middle and anterior ectosylvian gyral surfaces, and longer penetrations were made into the dorsal and ventral banks and fundus of the anterior ectosylvian sulcus. The quantitative and qualitative auditory response characteristics of neurons and neuron clusters in the sulcal banks and surrounding regions were mapped in detail, and the degree of overlap of auditory and visual neurons within the sulcus was determined by routinely testing for responsiveness to a gross light flash.

The detailed results from three animals and a summary of all penetrations into the sulcus are presented. The anterior ectosylvian sulcal field (Field AES) lay deep within the banks and fundus of the posterior three quarters of the sulcus. A combination of changes in the auditory response characteristics of neurons (i.e., in optimal stimulus, latency, and frequency tuning), and the presence of visually responsive cells, distinguished this field from surrounding fields. The distinction between the anterior ectosylvian field and extensions of the nearby tonotopic fields (i.e., primary and anterior auditory fields) into the dorsal and ventral banks of the dorsoposterior sector of the sulcus was readily made on the basis of these characteristics. The distinction between the anterior ectosylvian field and extensions of the second auditory field into the ventral bank of the middle sector of the sulcus was more difficult and there were differences between animals in the transition between these fields. Anterior ectosylvian sulcal field responses did not extend into the dorsal bank in anterior parts of the sulcus but were restricted to fundal regions, an observation consistent with the presence of the fourth somatosensory field in the dorsal bank of this sector of the sulcus. The majority of penetrations into the sulcus revealed coextensive auditory and visual activity, an observation apparently at variance with the identification of a purely visual field in this region. Barbiturate anaesthesia, which has been used in experiments demonstrating an anterior ectosylvian visual area, was found to have a depressing effect on auditory responses within the anterior ectosylvian sulcal field.
The dopaminergic amacrine cell
Authors: Dacey Dennis M.
Published: January 2005

The detailed morphology of the dopaminergic amacrine cell type has been characterized in the macaque monkey retina by intracellular injection of horseradish peroxidase (HRP). This cell type was recognized by its large soma in an in vitro, wholemount preparation of the retina stained with the fluorescent dye, acridine orange. HRP‐fills revealed a large, sparsely branching, spiny dendritic tree and a number of extremely thin, axon‐like processes that arose from the soma and proximal dendrites. The axon‐like processes were studded with distinct varicosities and were traced for up to 3 mm beyond the dendritic tree. The true lengths of the axon‐like processes were greater than 3 mm, however, because the HRP reaction product consistently diminished before an endpoint was reached. Both the dendrites and the axon‐like processes were narrowly stratified close to the outer border of the inner plexiform layer, although in a few cases single axon‐like processes projected into the outer nuclear and outer plexiform layers.

The HRP‐filled amacrines appeared equivalent to a subpopulation of neurons that are intensely immunoreactive for tyrosine hydroxylase (TH). TH‐immunoreactive cells showed a nearly identical soma size and dendritic field size range, the same pattern of dendritic branching and spiny morphology, and also gave rise to distinct axon‐like processes from both the soma and proximal dendrites.

To test this correspondence more directly, the large acridine stained cells were injected with Lucifer Yellow and the retina was subsequently processed for TH immunoreactivity using diaminobenzidine as the chromagen. In all cases Lucifer Yellow injected cells also showed intense TH immunoreactivity.

Spatial densities of the TH amacrine cells were therefore used to calculate coverage factors for the dendritic trees and for the axon‐like components of the HRP‐filled cells. The axon‐like processes showed a coverage factor of at least 300, about 100 times that of the dendritic fields. This great overlap could be directly observed in TH‐immunoreacted retinal wholemounts as a dense plexus of fine, varicose processes. The density of the TH plexus is greater than the density predicted from the lengths (1–3 mm) of the HRP‐filled axon‐like processes however, and suggests that the axon‐like processes have an actual length of about 4–5 mm.

The dual morphology of the dopaminergic amacrine, coupled with the previous studies of identified dopaminergic synapses, suggests the hypothesis that the varicosities on the axon‐like processes are the major source of synaptic output, and that the spiny dendrites are the major recipients of synaptic input from cone bipolar cells and other amacrine cells.

The rare extension of the axon‐like processes into the outer plexiform layer, and current understanding of the morphology of dopaminergic interplexiform cells in teleost fish, supports the hypothesis that the dopaminergic amacrine and interplexiform cells represent a single cell type in which there is quantitative variation across species in the projection pattern of the axon‐like processes.
Molecular identification of the lugaro cell in the cat cerebellar cortex
Authors: Sahin Mustafa , Hockfield Susan
Published: January 2005

The cerebellar cortex contains five major classes of neurons that can be differentiated from one another on the basis of their location, size, shape, and, in some cases, molecular characteristics. The cerebellar cortex also contains other, less numerous neuronal types, including the Lugaro cell, which has been described on only a few occasions. The Lugaro cell is a relative rare cell type and is characterized by a fusiform cell body with thick, horizontally oriented dendrites. It is located in or slightly below the Purkinje cell layer. Because the Lugaro cell shares some morphological characteristics with the other large granular layer neurons, it often has been classified as a Golgi cell.

In the present study we have taken advantage of differences in the molecular properties of neurons and have used monoclonal antibodies to identify and classify the Lugaro cell. Three large neuronal types in the cerebellar cortex were examined with cell‐type‐specific antibodies: Cat‐301 and Cat‐304 for Lugaro cells; Rat‐303 for Golgi cells; and anti‐calbindin for Purkinje cells. Double label immunocytochemistry on sections of the cat cerebellum was performed with subclass‐ or species‐specific secondary antibodies. Each of the three antibodies was selective for one of the three large neuron classes. Cat‐301 and Cat‐304 recognized Lugaro cells but not Golgi or Purkinje cells.

Our results demonstrate that the Lugaro cells are molecularly, as well as morphologically, distinct from Purkinje and Golgi cells and thus constitute a distinct cell type in the cerebellar cortex.
An intracellular study of respiratory neurons in the rostral ventrolateral medulla of the rat and their relationship to catecholamine‐containing neurons
Authors: Pilowsky Paul M. , Jiang Chun , Lipski Janusz
Published: January 2005

Intracellular recording and labelling with Lucifer yellow of respiratory neurons in the rostral ventrolateral medulla were carried out in urethane‐anaesthetised rats. A combined immunofluorescence and immunoperoxidase technique enabled an assessment of the tyrosine hydroxylase immunoreactivity, as well as an examination of the morphology of inspiratory and expiratory neurons in this part of the medulla oblongata. The results demonstrate: (a) that respiratory neurons in the rostral ventrolateral medulla of the rat are intermingled with catecholamine‐containing neurons of the C1 cell group, but are not themselves catecholamine‐containing; (b) that many non‐spinally projecting respiratory neurons have axonal arborisations within the ventrolateral medulla in the same region as the C1 cell group, other respiratory neurons, and neurons reported to have a cardiovascular function; and (c) that the dendrites of respiratory neurons in this region radiate throughout the ventrolateral medulla and frequently approach the ventral surface.
Primate supplementary eye field: I. Comparative aspects of mesencephalic and pontine connections
Authors: Shook B. L. , Schlag‐Rey M. , Schlag J.
Published: January 2005

WGA‐HRP was used to examine projections to the brainstem from the supplementary eye field (SEF). The SEF was defined electrophysiologically in awake, behaving monkeys and connections were compared to those of the arcuate frontal eye field (FEF), area 6DC, and primary motor cortex. The SEF was found to have either direct or indirect connections with almost every known pre‐ and paraoculomotor structure of the brainstem. The SEF was found to project bilaterally to layers I and IV of a tangentially widespread region of the superior colliculus. Terminal label was evident in the pretectal olivary nucleus, nucleus of the optic tract, nucleus raphe interpositus (omnipause region), nucleus prepositus hypoglossi, the perioculomotor cap of the central gray, dorsal central gray, nucleus reticularis tegmenti pontis, nucleus reticularis pontis oralis, and to multiple nuclei of the basis pontis (most densely to the dorsomedial nucleus). Bilateral projections were found in the parvicellular red nucleus. Reciprocal connections were present in the nucleus limitans, the mesencephalic reticular formation, locus coeruleus, and the serotonergic nuclei of the raphe complex (dorsalis and central superior). Overall patterns of connectivity were similar to those of the FEF and markedly different from those of the contiguous dorsocaudal area 6 or primary motor cortex. It was concluded that observed patterns of SEF‐brainstem connectivity further justifies viewing this region as a distinct eye field that is likely to serve preparatory and trigger functions in the generation of saccadic eye movements.
Morphological types of projection neurons in layer 5 of cat visual cortex
Authors: Hübener Mark , Schwarz Cornelius , Bolz Jürgen
Published: January 2005

Pyramidal cells in layer 5 of the visual cortex have multiple cortical and subcortical projection sites. Previous studies found that many cells possess bifurcating axons and innervate more than one cortical or subcortical target, but cells projecting to both cortical and subcortical targets were not observed. The present study examines the morphology of cells in cat visual cortex projecting to the superior colliculus, the main subcortical target of layer 5, and cells in layer 5 projecting to cortical areas 18 and 19. The neurons that give rise to these different projections were retrogradely labelled and intracellularly stained in living brain slices.

Our results show that cells within each projection group have several morphological features in common. All corticotectal cells have a long apical dendrite forming a large terminal tuft in layer 1. Their cell bodies are medium sized to large, and their basal dendrites form a dense and symmetrical dendritic field. Corticocortical cells in layer 5 have a very different morphology: their apical dendrites are short and they never reach higher than layers 2/3. Their cells bodies are small to medium sized and they have fewer basal dendrites than corticotectal cells. Thus there are two morphologically distinct projection systems in layer 5, one projecting to cortical and the other one to subcortical targets, suggesting that these two systems transmit different information from the visual cortex.

Among the corticotectal cells with the largest cell bodies we found some cells whose basal and apical dendrites were almost devoid of spines. Spiny and spinefree corticotectal cells also have different intrinsic axon collaterals and therefore play different roles in the cortical circuitry. While many spiny corticotectal cells have axon collaterals that project to layer 6, spinefree corticotectal cells have fewer axon collaterals and these do not arborize in layer 6. We suggest that the two morphological types of corticotectal cells might be related to functional differences known to exist among these cells. We discuss how the presence or absence of spines affects the integration of the synaptic input and how this might be related to the cells' functional properties.
Morphological changes of the myenteric plexus neurons in the bullfrog (Rana catesbeiana) duodenum during metamorphosis
Authors: Torihashi Shigeko
Published: January 2005

Myenteric plexus neurons of the duodenum in the bullfrog Rana catesbeiana were examined during metamorphosis by the Gros‐Bielschowsky silver impregnation method and electron microscopy.

Larval type neurons with slender and curved cell soma were recognized in the duodenum of the premetamorphic tadpole. They degenerate and decrease in number during early metamorphic climax through shrinkage of the cell soma and autolysis of the cytoplasm. These larval type neurons reduce to debris and then disappear. Two new cell types (adult type neurons) subsequently appear. These new neurons develop and increase in number during late climax and after metamorphosis. Those that appear first are large type A neurons each with a prominent axon and they stain darkly with silver. They enlarge during late stages. Subsequently small type B neurons appear which stain weakly with silver. They increase the number of their dendrites, change their shape, but enlarge only slightly during late development.

In summary, therefore, it is concluded that during metamorphosis, the larval myenteric plexus neurons in the bullfrog duodenum are replaced by two new populations of adult neurons.
Terminal arbors of individual, physiologically identified geniculocortical axons in the tree shrew's striate cortex
Authors: Raczkowski Denis , Fitzpatrick David
Published: January 2005

We studied the terminal patterns of single, physiologically identified geniculocortical axons in the striate cortex of the tree shrew by using intracellular recording and labeling methods. Axons were classified by their response to the onset (ON‐center) or offset (OFF‐center) of a light stimulus presented to the ipsilateral or contralateral eye. Then, we attempted to penetrate each axon for labeling with horseradish peroxidase. We recovered 23 axons and studied 16 of these in detail. Light microscopic reconstructions of these axons revealed several distinct terminal patterns within cortical layer IV. ON‐center axons had terminal arbors that ended mainly in the upper part of layer IV (IVa), while OFF‐center axons ended in the lower part of layer IV (IVb). Within layers IVa and IVb, axons driven by the ipsilateral eye and those driven by the contralateral eye had overlapping distributions. However, their terminal arbors differed in size, in shape, and in the number of boutons. Compared with contralateral eye arbors, ipsilateral eye axons were on average three times larger in lateral extent (925 μm vs. 325 μm), spread over four times the surface area (0.13 mm2 vs. 0.03 mm2), and supported one and one‐half times as many terminal boutons (1,647 vs. 1,086). The ipsilateral eye axons had more boutons at the edges of layer IV (i.e., the upper part of layer IVa and the lower part of layer IVb), while those from the contralateral eye axons were more evenly distributed. These results show that each functional class of geniculocortical fiber has a different laminar and areal arrangement of boutons and we consider the significance of these differences for visual cortical function.
Plasticity of GABA‐ and glutamate‐containing terminals in the mouse thalamic ventrobasal complex deprived of vibrissal afferents: An immunogold‐electron microscopic study
Authors: Hámori J. , Takács J. , Verley R. , Petrusz P. , Farkas‐Bargeton E.
Published: January 2005

GABA and glutamate immunogold staining demonstrated that nerve cells of the thalamic ventrobasal complex (VB) of mice were positive exclusively for glutamate. None of the neuronal perikarya reacted the GABA antibody. By using alternate thin sections of the normal VB, it was also shown that large “specific” somatosensory and small corticothalamic terminals, both of which contained spherical synaptic vesicles, exhibited only glutamate‐like immunoreactivity. A third axonal type, containing flat‐ovoid synaptic vesicles, stained only for GABA.

Seventy‐five days after coagulation of the vibrissal follicles in newborn mice, a characteristic multiplication of GABA positive axon terminals was observed. In addition, it was demonstrated that, similarly to modified cortical endings (Hámori et al., J. Comp. Neurol. 254:166–183, '86), many GABA positive terminals appeared as specific afferent endings, replacing the missing “specific” vibrissal afferents. This finding shows a remarkable plasticity of inhibitory GABA axons during developmental synaptogenesis and provides further evidence that the size, location, and the type of attachment of presynaptic terminals are dependent on their postsynaptic target.