bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency tuning properties of neurons in the inferior colliculus of an FM bat
Authors: Casseday J. H. , Covey E.
Published: January 2005

We examined frequency tuning characteristics of single neurons in the inferior colliculus of the echolocating bat, Eptesicus fuscus, in order to determine whether there are different classes of spectral selectivity at this level and to relate frequency tuning properties to the design of the echolocation signal. In unanesthetized but tranquilized animals, we recorded responses from 363 single units to pure tones, frequency‐modulated (FM) sweeps, or broad‐band noise. Most units were selective for stimulus type; 50% responded only to pure tones, 14% responded only to FM sweeps, and 5% responded only to noise. The remainder responded to two or more types of stimuli. Tuning curves could be classified as follows: 1) V‐shaped tuning curves (57%) were the most common type; 2) closed tuning curves (20%) had thresholds at both low and high sound levels; 3) narrow filters (14%) had Q values above 20 at 10 dB and 30 dB above threshold or 10 dB and 40 dB above threshold; 4) frequency‐opponent tuning (6%) was found in units with high spontaneous activity; within a center range of frequencies, firing rate increased above spontaneous level, but at higher or lower frequencies, firing rate decreased below spontaneous level; 5) double‐tuned units (3%) had two best frequencies (BF). The most clear evidence of topographic distribution was seen for filter units, which were only found in the dorsal part of the 20–30 kHz isofrequency contour. Filter units were also the most clearly related to the echolocation signal of the bat. Their BFs were all within the range of the dominant frequency (˜20–30 kHz) that Eptesicus uses during the searching phase of echolocation. © 1992 Wiley‐Liss, Inc.
The somatosensory thalamus of monkeys: Cortical connections and a redefinition of nuclei in marmosets
Authors: Krubitzer Leah A. , Kaas Jon H.
Published: January 2005

Thalamic connections of three subdivisions of somatosensory cortex in marmosets were determined by placing wheatgerm agglutinin conjugated with horseradish peroxidase and fluorescent dyes as tracers into electrophysiologically identified sites in S‐I (area 3b), S‐II, and the parietal ventral area, PV. The relation of the resulting patterns of transported label to the cytoarchitecture and cytochrome oxidase architecture of the thalamus lead to three major conclusions. 1) The region traditionally described as the ventroposterior nucleus (VP) is a composite of VP proper and parts of the ventroposterior inferior nucleus (VPi). Much of the VP region consists of groups of densely stained, closely packed neurons that project to S‐I. VPi includes a ventral oval of pale, less densely packed neurons and finger‐like protrusions that extend into VP proper and separate clusters of VP neurons related to different body parts. Neurons in both parts of VPi project to S‐II rather than S‐I. Connection patterns indicate that the proper and the embedded parts of VPi combine to form a body representation paralleling that in VP. 2) VPi also provides the major thalamic input into PV. 3) In architecture, location, and cortical connections, the region traditionally described as the anterior pulvinar (AP) of monkeys resembles the medial posterior nucleus, Pom, of other mammals and we propose that all or most of AP is homologous to Pom. AP caps VP dorsomedially, has neurons that are moderately dense in Nissl staining, and reacts moderately in CO preparations. AP neurons project to S‐I, S‐II, and PV in somatotopic patterns. © 1992 Wiley‐Liss, Inc.
Proportion of glutamate‐ and aspartate‐immunoreactive neurons in the efferent pathways of the rat visual cortex varies according to the target
Authors: Dori I. , Dinopoulos A. , Cavanagh M. E. , Parnavelas J. G.
Published: January 2005

Immunohistochemistry, with antisera directed against glutamate (Glu) or aspartate (Asp), was combined with wheat germ agglutinin—horseradish peroxidase (WGA‐HRP) histochemistry to examine the distribution, morphology, and proportions of Glu‐ and Asp‐containing neurons that give rise to corticofugal and callosal projections of the rat visual cortex.

WGA‐HRP injections in the dorsal lateral geniculate nucleus resulted in retrograde labelling of small and medium‐sized cells throughout layer VI of the visual cortex. Of these cells, 60% were also Glu‐immunoreactive and 61% Asp‐positive. WGA‐HRP injections in the superior colliculus labelled large and medium‐sized neurons in the upper portion of layer V of the visual cortex. Of these cells, 46% were also stained for Glu and 66% for Asp. Injections in the pontine nuclei resulted in retrograde labelling of cells in the deeper part of cortical layer V. Retrogradely labelled cells, which were also immunoreactive for Glu or Asp, were large pyramidal cells. Corticopontine neurons, which were also Glu‐positive, accounted for 42% of the total number of WGA‐HRP labelled cells, whilst for Asp‐positive neurons this percentage was 51%. Finally, after injections in the visual cortex, retrogradely labelled small and medium‐sized cells were found throughout layers II–VI in the contralateral visual cortex. Of these neurons, 38% were also labelled for Glu while 49% were also Asp‐immunoreactive.

The present results demonstrate that substantial proportions of projection neurons in the rat visual cortex are immunoreactive for Glu or Asp, suggesting that these excitatory amino acids are the major transmitters used by the cortical efferent systems examined. Furthermore, the proportions of these immunoreactive neurons in the efferent pathways vary according to the target. © 1992 Wiley‐Liss, Inc.
Distribution of neuropeptide Y‐like immunoreactivity in the brain of the lizard Gallotia galloti
Authors: Medina Loreta , Martí Elisa , Artero Cristina , Fasolo Aldo , Puelles Luis
Published: January 2005

The distribution of neuropeptide Y (NPY)‐like immunoreactivity was studied in the brain of the lizard Gallotia galloti, in order to gain insight into the comparative topography of this peptide. Antisera against both NPY and its C‐terminal flanking peptide (C‐PON) were used, demonstrating a general coexistence of both peptides, as described in other vertebrates.

Most NPY‐like immunoreactive (NPY‐LI) cell bodies were observed in the telencephalon, specifically in various olfactory structures, all cortices, septum, basal ganglia (except for the globus pallidus), the nucleus of the diagonal band of Broca, the amygdaloid complex, and the bed nucleus of the anterior commissure. NPY‐LI cells were also seen in the preoptic and hypothalamic regions and the dorsal thalamus (mainly in the perirotundal belt), as well as in the mesencephalic tegmentum (in the ventral tegmental area, the substantia nigra, and the retrorubral area). NPY‐LI fibers and terminals were widely distributed in the brain. All visual and auditory neuropiles were densely innervated. Specially dense plexuses were seen in the nucleus accumbens, the ventral pallidum, the suprachiasmatic and ventromedial hypothalamic nuclei, the nucleus medialis thalami, the left habenula, and the central nucleus of the torus semicircularis.

Our analysis shows that the distribution of NPY‐like immunoreactivity in the forebrain of Gallotia largely resembles that of other vertebrates, whereas differences are mainly observed in the brainstem. The widespread distribution of NPY in the lizard brain suggests several modulatory functional roles, either in local‐circuit systems of the forebrain, or in various limbic, neuroendocrine, and sensory pathways. © 1992 Wiley‐Liss, Inc.
Functional organization of vagal reflex systems in the brain stem of the goldfish, Carassius auratus
Authors: Goehler Lisa E. , Finger Thomas E.
Published: January 2005

The coordination of secretory and motor responses to food within the alimentary canal requires well organized brain stem reflex systems. In the goldfish, Carassius auratus, three vagal reflex systems control three phases of ingestion and digestion. The orobranchial system sorts food from substrate, the pharyngeal chewing organ prepares items deemed to be food for digestion and absorption, and the abdominal system regulates the digestion of food. Each system is represented in the central nervous system by separate sensory and motor nuclei. The aim of the present study was to determine whether the interrelationships among the vagal sensory and motor nuclei reflect the peripheral organization.

The sensory nucleus of each vagal system was injected with the neuronal tracer horseradish peroxidase (HRP), in separate cases. HRP injections into the vagal lobe sensory layers (orobranchial system) labeled fibers projecting topographically to the vagal lobe motor layer, but not at all to the pharyngeal or abdominal motor nuclei. Similarly, injections of HRP into the pharyngeal and abdominal sensory nuclei selectively labeled nerve fibers projecting to the pharyngeal and abdominal motor nuclei, respectively. All injections resulted in labeled fibers and/or cells in the lateral reticular formation, and in fibers ascending in the secondary gustatory‐visceral tract. Gustatory information from the pharynx is apparently processed in the same brain stem system as pharyngeal general visceral information, suggesting that functional or regional characteristics of visceral sensory information may be more important for brain stem processing than the traditional “special” (gustatory) versus “general” visceral dichotomy. These results indicate that anatomically and functionally separate reflex systems exist within the goldfish vagal visceral nuclei. © 1992 Wiley‐Liss, Inc.
Dorsal mesencephalic projections to pons, medulla, and spinal cord in the cat: Limbic and non‐limbic components
Authors: Cowie Robert J. , Holstege Gert
Published: January 2005

The vertebrate dorsal mesencephalon consists of the superior colliculus, the dorsal portion of the periaqueductal gray, and the mesencephalic trigeminal neurons in between. These structures, via their descending pathways, take part in various behavioral responses to environmental stimuli. This study was undertaken to compare the origins and trajectories of these pathways in the cat.

Injections of horseradish peroxidase into the cervical spinal cord and upper medullary medial tegmentum retrogradely labeled cells mainly in the contralateral intermediate and deep superior colliculus, and in the ipsilateral dorsal and lateral periaqueductal gray and adjacent tegmentum. Only injections in the medullary lateral tegmental field labeled mesencephalic trigeminal neurons ipsilaterally.

Autoradiographic tracing results, based on injections across the dorsal mesencephalon, revealed three efferent fiberstreams. A massive first fiberstream (limbic pathway), consisting of thin fibers, descended ipsilaterally from the dorsal and lateral periaqueductal gray and adjacent superior colliculus through the mesencephalic and pontine lateral tegmentum, terminating in these areas as well as in the ventral third of the caudal pontine and medullary medial tegmentum. A few fibers from the dorsal periaqueductal gray matter (PAG) were distributed bilaterally to the dorsal vagal, solitary, and retroambiguus nuclei. The second fiberstream (the predorsal bundle) descended contralaterally from the superior colliculus (SC) and consisted of both thick and thin labeled fibers. The thin fibers terminated bilaterally in the dorsomedial nucleus reticularis tegmenti pontis and the medial half of the caudal medial accessory inferior olive. The thick fibers targeted the contralateral dorsal two thirds of the caudal pontine and medullary medial tegmental fields, and the facial, abducens, lateral reticular, subtrigeminal, and prepositus hypoglossi nuclei. A few fibers recrossed the midline to terminate in the ipsilateral medial tegmentum. Caudal to the obex, fibers terminated laterally in the tegmentum and upper cervical intermediate zone. From the lateral SC, fibers terminated bilaterally in the lateral tegmental fields of the pons and medulla and lateral facial subnuclei. The third fiberstream (mesencephalic trigeminal or Probst tract) terminated in the supratrigeminal and motor trigeminal nuclei, and laterally in the tegmentum and upper cervical intermediate zone.

In summary, neurons in the PAG and in the deep layers of the SC give rise to a massive ipsilateral descending pathway, in which a medial‐to‐lateral organization exists. A similar topographical pattern occurs in the crossed SC projections. The possibility that these completely different descending systems cooperate in producing specific defensive behaviors is discussed. © 1992 Wiey‐Liss, Inc.
Distribution of immunoreactivity for γ‐aminobutyric acid in the salamander olfactory bulb
Authors: Hamilton Kathryn A.
Published: January 2005

Intrinsic neurons provide inhibitory synaptic input to mitral (and tufted) output cells within several laminae of the olfactory bulb. In rodents, the two main types of intrinsic neurons are granule and periglomerular cells, both of which contain γ‐aminobutyric acid (GABA). In the present study, immunocytochemical techniques were used to determine whether intrinsic neurons in the salamander olfactory bulb might also contain GABA.

With the aid of two antisera to different GABA‐conjugates, immunoreactivity for GABA was localized within the olfactory bulb laminae. In the glomerular layer, periglomerular cells, which were strongly immunoreactive, were concentrated in clusters along the border with the olfactory nerve layer. Dendrites of the cells encircled nearby glomeruli and were presumably a primary source of intraglomerular processes that were also stained. In the subglomerular region and external plexiform layer, relatively few immunoreactive cells were observed, most of which appeared to be periglomerular and tufted cell types with glomerular dendrites. Throughout the external plexiform and mitral cell layers, however, a dense matrix of spiny processes and puncta was stained, outlining large, unstained dendrites derived from the large, unstained cell bodies of mitral cells. The spiny processes and puncta appeared to be derived from granule cells, which were the most abundant immunoreactive cells in the bulb. Granule cell bodies filled the granule cell layer.

In tissue fixed with 0.1–0.2% glutaraldehyde, staining in the olfactory bulb laminae was blocked by preadsorption of the two antisera with glutaraldehyde‐conjugated GABA‐bovine serum albumin. The staining therefore appeared to be specific for fixed GABA. The distribution of GABA immunoreactivity in the salamander olfactory bulb suggests that several types of GABAergic interneurons that branch in the glomerular, external plexiform, and mitral cell layers may influence the activity of mitral (and tufted) output cells. © 1992 Wiley‐Liss, Inc.
Serotoninergic projections from the raphe nuclei to the preoptic area in sheep as revealed by immunohistochemistry and retrograde labeling
Authors: Tillet Yves
Published: January 2005

A retrograde tracer, fluorogold, was injected into the sheep preoptic area in order to demonstrate the origin of the serotoninergic fibers observed in this area. Within the raphe nuclei, retrogradely fluorogold‐labeled neurons were observed mainly in the median raphe nucleus (B8), groups B6/B5, and in the area lateral to the nucleus interpeduncularis (group S4), but not in the dorsal raphe nucleus. About 50% of these fluorogold‐containing neurons were immunostained with a specific antiserum raised against serotonin. Double‐labeled neurons (serotonin‐immunoreactive and fluorogold containing neurons) represented less than 20% of the whole number of serotoninergic neurons. We concluded that a few serotoninergic neurons in the median raphe nucleus and in groups B5/B6 and S4 project to the preoptic area. Moreover, these nuclei contained non‐serotoninergic neurons which project to the same area. These results give new information on the serotoninergic innervation of the preoptic area in the sheep.
Early stages in the development of spinal motor neurons
Authors: Chen Edmond W. , Chiu Arlene Y.
Published: January 2005

In order to identify early events in the differentiation of motor neurons, the expression of several developmentally regulated, neuronal molecules was investigated by immunohistochemistry on consecutive sections of cervical spinal cord. Motor neurons are among the first neurons to be born and to differentiate within the embryonic rat spinal cord. They undergo their terminal mitosis on embryonic days 10 and 11 (E10–11) and acquire detectable levels of the transmitter synthesizing enzyme, choline acetyltransferase, by E11.5. Staining with antibodies to the 68 kD neurofilament protein revealed motor neurons extending processes out the ventral root as early as E10.5. Monoclonal antibodies to two different epitopes on the cell adhesive molecule, NCAM, bound to myotomes on E10.5, and began to recognize ventral horn neurons by E11. Two other markers of developing neurons, the growth‐associated protein, GAP‐43, and the surface glycoprotein, TAG‐1, were clearly detected on young motor neurons by E11.5. Thus, during the 36 hours following the final mitosis of their precursors, motor neurons acquire cytoskeletal, enzymatic, and cell surface components that distinguish them from other developing cells within the spinal cord.

Not all of the newly acquired molecules continue to be expressed by motor neurons. Immunoreactivity for TAG‐1 was lost by E12.5, followed by a gradual reduction of immunoreactivity for GAP‐43 and the highly polysialylated form of NCAM. By E15, only antibodies to choline acetyltransferase (Phelps et al., J. Comp. Neurol. 307:1–10, 1990), and to neurofilaments, selectively stained motor neurons within the embryonic spinal cord. The transient presence of GAP‐43, TAG‐1, and the embryonic form of NCAM coincides with a period of vigorous axonal growth and declines when motor neurons reach their targets. This report describes the temporal sequence of early stages in the differentiation of the rodent motor neuronal phenotype. Some of these changes may be related to interactions with their synaptic partners.
Heterogeneous development of calbindin‐D28K expression in the striatal matrix
Authors: Liu Fu‐Chin , Graybiel Ann M.
Published: January 2005

In the present study, we attempted to trace the development of the striatal matrix by analyzing the ontogenetic expression of calbindin‐D28K (calbindin), a calcium binding protein selectivity expressed in medium‐sized neurons of the matrix compartment of the mature rat's caudoputamen. The localization of calbindin was documented in a series of developing rat brains, as was the compartmental location of these cells relative to tyrosine hydroxylase (TH)‐immunostained dopamine islands, sites of future striosomes.

Medium‐sized striatal neurons appeared in the striatum at embryonic day (E) 20, and from their first appearance, the calbindin‐positive neurons had highly heterogeneous distributions. They first formed a latticework of patches and bands in a ventral region of the caudoputamen. By postnatal day (P) 7, this early calbindin‐positive lattice had evolved into a mosaic in which circumscript pockets of low calbindin‐like immunoreactivity appeared in more extensive calbindin‐rich surrounds. With further development, the mosaic gradually encroached on all but the dorsolateral caudoputamen, a district that is calbindin‐poor at adulthood. A special lateral branch of the striatal calbindin system was also identified, distinct from the rest of the calbindin‐positive mosaic in several developmental characteristics.

In the parts of the caudoputamen where the developing calbindin system and dopamine island system were both present, the dopamine islands invariably lay in calbindin‐poor zones. Most dopamine islands, however, only filled parts of the corresponding calbindin‐poor zones. Moreover, there were some calbindin‐poor zones for which TH‐positive dopamine islands could not be detected. Thus during development, calbindin was expressed in the extrastriosomal matrix of the striatum, but the matrix could be divided into calbindin‐rich and calbindin‐poor zones. In the calbindin‐rich regions, there were patches of especially intense calbindin expression and zones of weaker expression.

These results suggest that there is neurochemical heterogeneity in the striatal matrix during the prolonged developmental period in which the early calbindin‐positive lattice expands to form the calbindin‐positive matrix of the mature striatum. Surprisingly, calbindin expression in the matrix, although eventually distributed in strictly complementary fashion to striosomes, does not originate as a system complementary to dopamine islands. The prolonged disparity between the borders of dopamine islands and calbindin‐poor zones, and the different spatiotemporal schedules of development of the islands and the calbindin gaps suggest instead that the final match between the borders of striosomes and surrounding matrix results from dynamic processes occurring early in postnatal development. Candidate mechanisms for the gradual adjustment of these borders are proposed.
The tectorecipient zone in the inferior olivary nucleus in the rat
Authors: Akaike Tadashi
Published: January 2005

Tecto‐olivary and olivocerebellar projections in the rat were investigated in order to identify the tectorecipient zone in the inferior olivary nucleus and to determine whether inferior olivary neurons projecting to the cerebellar tecto‐olivo‐recipient zones (lobule VII, crus II, lobulus simplex, and paramedian lobule) originate in the different regions within the tectorecipient zone. An electrophysiological method and an axonal transport technique of wheat‐germ agglutinin‐conjugated horseradish peroxidase were used. The tectorecipient zone was identified in the caudomedial region of the medial accessory olive. Neurons projecting to lobule VII originated in the caudomedial region of the tectorecipient zone, but those to crus II, lobulus simplex, and paramedian lobule originated in its rostrolateral region. These observations suggest that there are two independent tecto‐olivo‐cerebellar systems: (1) superior colliculus—the medial region of the tectorecipient zone—lobule VII—the caudomedial region of the fastigial nucleus; and (2) superior colliculus—the rostrolateral region of the tectorecipient region—crus II, lobulus simplex, and paramedian lobule—the dorsolateral protuberance of the fastigial nucleus.
II. Localization of Pi class glutathione‐S‐transferase in the forebrains of neonatal and young rats: Evidence for separation of astrocytic and oligodendrocytic lineages
Authors: Cammer Wendy , Zhang Hong
Published: January 2005

The Yp isoform (Pi class) of glutathione‐S‐transferase has recently been localized in oligodendrocytes in the brains of mature rats. To examine at what postnatal age Pi first appears in oligodendrocytes or precursor cells, antibodies against Pi were used to immunostain tissue sections from the forebrains of neonatal rats and young rats up to 17 days of age. In the brains of neonates Pi immunofluorescence was observed in ovoid cells in the subependymal layer, and in ovoid cells and cells bearing short, thick processes in the corpus callosum and cingulum. These cells did not immunostain for vimentin. During the first postnatal week Pi‐positive cells showed positive immunostaining for ganglioside GD3, which is characteristic of oligodendrocyte precursors, and process‐bearing Pi‐positive cells appeared in the cingulum and at the lateral borders of the corpus callosum in increasing numbers. During the second postnatal week the cytoplasm of Pi‐positive cells became more compact, and the processes thinner, and the Pi‐positive cells and their processes began to immunostain for 2′,3′‐cyclic nucleotide‐3′‐phosphohydrolase, which is characteristic of immature and mature oligodendrocytes and myelin sheaths. By age 17 days Pi was observed in relatively mature oligodendrocytes. The observations suggest that Pi occurs in oligodendrocyte precursors, immature oligodendrocytes, and mature oligodendrocytes in the postnatal through 17 day old rat forebrain.

In the accompanying paper (Cammer and Zhang, '92)—if references are permitted in the Abstract a different glutathione‐S‐transferase isoform, Yb (Mu class), was localized in cells of the astrocyte lineage, beginning in the forebrains of neonatal rats. At each postnatal age Mu‐and Pi‐positive cells differed in size and shape as well as in their contents of “marker” antigens. These findings support the conclusion that the oligodendrocyte and astrocyte lines have separate precursors in the neonatal rat forebrain. © 1992 Wiley‐Liss, Inc.
Spatial density and distribution of choline acetyltransferase immunoreactive cells in human, macaque, and baboon retinas
Authors: Rodieck R. W. , Marshak D. W.
Published: January 2005

Whole‐mounted human, macaque, and baboon retinas were labelled with an antiserum to human choline acetyltransferase (ChAT), by the immunoperoxidase technique. Previous work in nonprimate species has shown that these cells correspond to the starburst amacrine cells. Labelled somata were disposed on either side of the inner plexiform layer, and their processes formed two narrow zones within it.

In human retinas, the ratio of labelled somata in the ganglion cell layer (GCL) to those in the inner nuclear layer (nominal Sb/Sa ratio) was about 60/40 at all locations, similar to that found in nonprimate mammalian species. The density of labelled cells in the human GCL ranged from 1,000 to 1,150 mm−2 near the fovea to 300 to 400 mm−2 in the periphery. Labelling tended to be more erratic in macaque retinas. Nevertheless the Sb/Sa ratio was as high as 70/30 and spatial densities were similar to those of humans. The overlap factor in macaque retinas outside the nasal quadrant was about 10 at all retinal eccentricities, based upon dendritic‐field sizes from a Golgi study.

About each labelled soma there was a region 20 to 120 μm in diameter in which the probability of the occurrence of other labelled somata was lower than elsewhere. No such nonrandomness was found between labeled cells in the GCL and those in the amacrine cell layer. The packing factor was about 0.3 in well‐labelled regions, independent of retinal position or spatial density. Published data on ChAT‐labelled cells in rabbit and rat show a similar value. This invariance is consistent with the hypothesis that this nonrandomness is a residual consequence of somal contiguity at an early developmental stage. © 1992 Wiley‐Liss, Inc.
Anatomy and fine structure of neurons in the deutocerebral projection pathway of the crayfish olfactory system
Authors: Mellon De Forest , Alones Vinessa , Lawrence M. David
Published: January 2005

Golgi impregnation and neurobiotin injection were used to examine details of the neural pathways in the olfactory system of the freshwater crayfish, Procambarus clarkii. Deutocerebral projection neurons (globuli cells) were directly injected with neurobiotin. These neurons have dendritic arborizations in the ipsilateral olfactory and accessory lobes, and they project axons to the lateral protocerebrum, where they terminate in microglomeruli of the hemiellipsoid body. The axons of the deutocerebral projection neurons are readily impregnated by Golgi procedures, and they terminate as an expanded membranous knot about 5 μm in diameter. Electron microscopy on Golgi‐stained terminals has revealed that each knot makes several hundred synapses with small spine‐like or shaft‐like processes of postsynaptic neurons. Injection of neurobiotin into local interneurons of the hemi‐ellipsoid body and subsequent examination of stained preparations with the electron microscope reveals that these cells are a major postsynaptic target of the deutocerebral projection neurons. Furthermore, the local interneurons make extensive efferent synaptic connections with unidentified neurons in the terminal medulla. © 1992 Wiley‐Liss, Inc.
Callosal and superior temporal sulcus contributions to receptive field properties in the macaque monkey's nucleus of the optic tract and dorsal terminal nucleus of the accessory optic tract
Authors: Hoffmann K.‐P. , Distler C. , Ilg U.
Published: January 2005

To assess the functional contribution of the cortical input to the receptive field properties of nucleus of the optic tract (NOT) and dorsal terminal nucleus (DTN) neurons, a first set of experiments evaluated the response properties of NOT‐DTN cells in monkeys with split corpus callosum. With respect to visual latency, direction specificity, directional tuning width, velocity tuning, ocular dominance, and binocular interaction, they were indistinguishable from NOT‐DTN neurons in normal monkeys. However, a clear difference was found regarding the extent of the receptive fields. Whereas, in normal monkeys, NOT‐DTN receptive fields include the contralateral hemifield and the fovea as well as substantial parts of the ipsilateral visual field, receptive fields in callosum‐split monkeys stop abruptly at, or close to, the vertical O‐meridian and do not extend into the ipsilateral visual field. In addition, the location of the highest sensitivity within the receptive fields in callosum‐split monkeys is shifted away from the vertical 0‐meridian in comparison to normal animals.

In a second set of experiments, we antidromically identified cortical neurons within the superior temporal sulcus that project to the NOT‐DTN. These neurons were found in area MT mostly near the border of MTp or MSTl. All of them are direction selective for ipsiversive stimulus movement, and their receptive fields extend substantially into the ipsilateral visual hemifield. Neurons with other preferred directions did not project to the NOT‐DTN.

These results contribute to the explanation of the ipsiversive directional deficits in slow eye movements after cortical lesions, as well as the asymmetries in optokinetic nystagmus with hemifield stimulation after transection of the corpus callosum. The more general implication of the results is that a particular function of a cortical area can only be understood by knowing its subcortical connections. © 1992 Wiley‐Liss, Inc.
Cortical afferents to behaviorally defined regions of the inferior temporal and parahippocampal gyri as demonstrated by WGA‐HRP
Authors: Martin‐Elkins Carol L. , Horel James A.
Published: January 2005

The inferior temporal gyrus in the monkey appears to be unique among the many extrastriate visual cortices in its importance for normal performance of delayed match‐to‐sample, a visual memory task. However, the anatomical pathway providing visual information to this portion of the temporal lobe remains unclear. In this study, wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) was injected into the anterior inferior temporal gyrus and heavy projections were found to arise in cytoarchitectural area TF of the parahippocampal gyrus, as well as moderate projections in more posterior portions of inferior temporal gyrus and perirhinal and entorhinal cortices. Subsequently, WGA‐HRP was injected into area TF, resulting in retrogradely labeled cells primarily located in the portions of area TF adjacent to the injection and also in the occipitotemporal sulcus including the ventral portion of the prestriate visual area V4. Moderate projections were found to originate from the dorsal region of area V4 in the lunate sulcus, portions of the caudal parietal lobe, the posterior bank of caudal superior temporal sulcus, and area OPT located at the tip of the superior temporal sulcus. The middle temporal gyrus, foveal prestriate cortex, and area TEO, a transitional area between temporal and occipital visual areas, were all free from retrogradely labeled cells. These latter areas are included in the well‐established anatomical system that is known to carry visual information from striate cortex through prestriate to eventually reach dorsal portions of inferotemporal cortex which is coincident with the temporal lobe visual area TE. It is suggested here that there is an additional ventral pathway into area TE as well, which includes projections through portions of the prestriate cortex, occipitotemporal sulcus, and parahippocampal gyrus, ultimately reaching the anterior inferior temporal gyrus, an area that may be specialized to hold visual information over brief periods of time. © 1992 Wiley‐Liss, Inc.
Ontogenesis of the pyramidal cell of the mammalian neocortex and developmental cytoarchitectonics: A unifying theory
Authors: Marín‐Padilla Miguel
Published: January 2005

The prenatal development of the mammalian neocortex has been analyzed, with the rapid Golgi method, in a variety of experimental animals (hamster, mouse, rat, and cat) and in humans. A new developmental conception of the structural organization of the mammalian neocortex is discussed. Neocortical development begins with the establishment of the primordial plexiform layer (PPL) which precedes and is a prerequisite for the subsequent formation of the cortical plate (CP). The formation of the CP occurs, in its entirety, within the PPL. During its development, three fundamental neuronal events occur: migration, early differentiation, and late maturation. All migrating neurons, travelling on radial glial fibers, reach layer I, develop an apical dendrite, and establish contacts with its elements. These newly differentiated neurons assume similar morphology resembling embryonic pyramidal cells. As such, an early differentiation stage common to all neurons of the CP is established. During the late maturation stage, all CP neurons acquire their specific phenotypic structural and functional features. Only pyramidal neurons retain and expand their original connections with layer I while other neuronal types lose these connections. The pyramidal cell is redefined in developmental terms: the neocortex's pyramidal cell is both structurally and functionally locked into position between layer I and the cortical depth of its soma. During mammalian evolution pyramidal cells are forced to structurally and functionally elongate their apical dendrite outwardly to accommodate an increasing amount of information without losing either their original anchorage to layer I or their cortical depth. This unique property of pyramidal neurons is considered to be a mammalian innovation. Based on these observations, a unifying developmental cytoarchitectonic theory applicable to all mammals is proposed. The theory considers the CP to be a mammalian innovation and to represent a single, stratified, and expanding telencephalic nucleus. The theory envisions the mammalian neocortex as an open biological system capable of progressive expansion by the recruitment and transformation of primitive neurons from upper layer II into pyramidal cells. Hence, the number of pyramidal cell strata increases over the course of mammalian phylogeny. The developmental roles of layer I in the migration of neurons, formation of the CP, unique morphology of pyramidal cells, and overall structural organization of the mammalian neocortex are emphasized. © 1992 Wiley‐Liss, Inc.
Changes in lamination and neuronal survival in the isthmo‐optic nucleus following the intraocular injection of tetrodotoxin in chick embryos
Authors: Péquignot Y. , Clarke P. G. H.
Published: January 2005

We have studied how the development of the isthmo‐optic nucleus (ION) is affected by electrical activity in the ION's axonal target territory, the contralateral retina. Electrical activity was blocked or reduced in the retina for various periods by tetrodotoxin injected intraocularly in different doses. The effects on the morphology of the retina appear to have been minor.

During the ION's period of naturally occurring neuronal death (embryonic days 12 to 17), the injections substantially reduced this neuronal death and disrupted the development of lamination in the contralateral ION; there was also a lesser reduction in neuronal death in the ipsilateral ION. The dose of tetrodotoxin required to affect lamination was lower than that affecting neuronal death. Thus, the effects on neuronal death and on lamination were independent, since either could occur without the other. These effects were mediated by retrograde signals (probably two or more) from the eye; they occurred too early for the alternative anterograde route via the optic tectum (which projects to the ION) to be responsible.

After embryonic day 17, the ION's response to intraocular tetrodotoxin changes abruptly from increased survival to total and rapid degeneration. © 1992 Wiley‐Liss, Inc.
Maintenance of targeting errors by isthmo‐optic axons following the intraocular injection of tetrodotoxin in chick embryos
Authors: Péquignot Y. , Clarke P. G. H.
Published: January 2005

We have studied the role of electrical activity in the elimination of axonal targeting errors, which is a normal process in brain development. The experiments were focussed on the isthmo‐optic nucleus (ION), which, in adults, projects in topographical order on the contralateral retina. During embryogenesis, however, a few isthmo‐optic neurons project to the ipsilateral retina, and many project to topographically inappropriate parts of the contralateral one; both kinds of targeting error are known to be eliminated by the deaths of the parent neurons.

We injected tetrodotoxin (TTX) intraocularly at embryonic days 13 and 15 and, on the latter, applied a retrograde label to the retina of the same eye. Embryos were fixed at embryonic day 17. In some embryos, the label was a peripherally placed fleck of the carbocyanine dye “diI”; the resulting retrogradely labeled neurons in the contralateral ION were much more widely scattered in the TTX‐injected embryos than in controls (errors in topography). In other embryos, the label was a solution of rhodamine‐B‐isothiocyanate (RITC) injected into the vitreous body; this yielded several ipsilaterally labeled isthmo‐optic neurons in the TTX‐injected embryos, but virtually none in the controls. The numbers of both kinds of aberrantly projecting neuron approached those previously reported near the beginning of the ION's period of neuronal death. We conclude that electrical activity plays an important role in the elimination of axonal targeting errors in the chick embryo's isthmo‐optic system. © 1992 Wiley‐Liss, Inc.
Area 3a in the cat II. Projections to the motor cortex and their relations to other corticocortical connections
Authors: Avendaño Carlos , Isla Alberto J. , Rausell Estrella
Published: January 2005

It is well known that area 3a in the cat may monosynaptically influence the activity of neurons in the motor cortex. Much less information is available, however, on the anatomy of these connections. By using single or combined injections of different retrograde axonal tracers, we investigated the topography (horizontal and laminar) of area 3a neurons projecting to the motor cortex, and the anatomical relationships between these neurons and those projecting to other areas (2, 5, and SII) which, in turn, project to the motor cortex. Area 3a projects to all parts of area 4γ, to area 4δ, and to the agranular area 6 in the lateral bank of the presylvian sulcus (area 6aγ), but not to other parts of areas 4 and 6. This projection exhibits a loose topographic organization along the mediolateral dimension of area 3a, and, in many cases, arises predominantly from the rostral half of this area.

Although single small injections in the motor cortex produced two or more separate patches of retrograde labeling in 3a, after simultaneous injections of fluorochromes in two separate loci there often appeared in area 3a overlapping populations of neurons which were labeled retrogradely by each of the dyes, but with very few double‐labeled neurons. In horseradish peroxidase (HRP) cases, 72% of area 3a neurons projecting to area 4γ were distributed in supragranular layers (mainly layer III), although the proportion of labeling in infragranular layers was larger when using fluorescent dyes. Double‐labeled cells predominated in infragranular layers. These results have a bearing upon the functional roles that have been attributed to area 3a, as a cortical locus involved in muscle sensation, and a cortical relay to the motor cortex of rapid feedback information from muscle activity during movement. © 1992 Wiley‐Liss, Inc.
Diencephalic projections from the superficial and deep laminae of the medullary dorsal horn in the rat
Authors: Iwata Koichi , Kenshalo Dan R. , Dubner Ronald , Nahin Richard L.
Published: January 2005

An important function of the medullary dorsal horn (MDH) is the relay of nociceptive information from the face and mouth to higher centers of the central nervous system. We studied the central projection pattern of axons arising from the MDH by examining the axonal transport of Phaseolus vulgaris‐leucoagglutinin (PHA‐L). Labeled axon and axon terminal distributions arising from the MDH were analyzed at the light microscopic level.

After large injections of PHA‐L into both superficial and deep laminae of the MDH in the rat, labeled axons were observed in the nucleus submedius of the thalamus (SUB), ventroposterior thalamic nucleus medialis (VPM), ventroposterior thalamic nucleus parvicellularis (VPPC), posterior thalamic nuclei (PO), zona incerta (ZI), lateral hypothalamic nucleus (LH), and posterior hypothalamic nucleus (PH).

Restriction of PHA‐L into only the superficial laminae resulted in heavy axon and varicosity labeling in the SUB, VPM, PO, and VPPC and light labeling in LH. In contrast, after injections into deep laminae, labeled axons were mainly distributed in ZI and PH; some were also in VPM and LH, and fewer still in PO and SUB. Varicosities in VPM, SUB, and PO were significantly larger than those in VPPC, ZI, LH, and PH. Varicosity density was highest in SUB and lowest in the VPPC.

We concluded that there are two distinct nociceptive pathways, one originating from the superficial MDH and terminating primarily in the dorsal diencephalon and the second originating from deep laminae of the MDH and terminating primarily in the ventral diencephalon. We propose that in the rat, input from the deeper laminae is primarily involved in the motivational‐affective component of pain, whereas input from the superficial MDH is related to both the sensory‐discriminative and motivational‐affective component of pain. Published by 1992 Wiley‐Liss, Inc.
Localization of kynurenine aminotransferase immunoreactivity in the rat hippocampus
Authors: Du Fu , Schmidt Werner , Okuno Etsuo , Kido Ryo , Köhler Christer , Schwarcz Robert
Published: January 2005

The localization and distribution of kynurenine aminotransferase (KAT), the biosynthetic enzyme of the excitatory amino acid receptor antagonist, kynurenic acid, was studied in the rat hippocampal formation with immunohistochemical methods. The enzyme was found mainly in glial cells that could be distinguished as 3 types on the basis of their shapes and locations. Typically, these cells shared the morphological features of astrocytes and exhibited glial fibrillary acidic protein immunoreactivity as demonstrated by a double‐labeling technique. The distribution of KAT‐containing glial cells was heterogeneous throughout the hippocampal formation. In the hippocampus, the stratum lacunosum‐moleculare of Ammon's horn and the hilus contained a higher density of KAT‐positive glial cells than other regions, whereas the lowest density of KAT glial cells was observed in the granule cell layer of the dentate gyrus and in the stratum radiatum of CA subfields. In the subicular complex, the density of KAT‐containing glial cells was generally higher in the superficial than in the deep layer. Hippocampal neurons exhibiting KAT immunoreactivity, distinguished as nonpyramidal cells, were very few in number and mainly distributed in strata oriens and pyramidale of Ammon's horn. Substantially more KAT‐positive neurons were observed in layers II and III of the subicular complex. The organization of cellular elements containing KAT may be of relevance for the function and possible dysfunction of kynurenic acid in the rat hippocampal formation. © 1992 Wiley‐Liss, Inc.
GABAergic neurons in the mammalian inferior olive and ventral medulla detected by glutamate decarboxylase immunocytochemistry
Authors: Fredette Barbara J. , Adams Joe C. , Mugnaini Enrico
Published: January 2005

Neurons containing glutamic acid decarboxylase (GAD) (presumed GABAergic neurons) were mapped by immunocytochemistry in the ventral medulla of rat, rabbit, cat, rhesus monkey, and human, with emphasis on the inferior olive. In all species, three categories of GABAergic neurons were identified: periolivary neurons in the gray matter and the white matter surrounding the inferior olive, internuclear neurons located in the white matter between the subnuclei of the inferior olive, and intranuclear neurons located within the olivary gray matter. The intranuclear GABAergic neurons of the inferior olive had a characteristic morphology which differed from non‐GABAergic olivary neurons; they were usually smaller, and, wherever their processes were stained, they had radiating, sparsely branching dendrites. They were also usually distinguished from the other GABAergic neurons by their smaller size. The intraolivary GABAergic neurons constituted only a minor proportion of the total olivary neuronal population, but they were concentrated in regions of the olive that varied by species. In the rat, they were situated in the rostral tip of the medial accessory olive and in the caudal subdivision of the dorsal accessory olive, while in the rabbit, they were located in the caudal two‐thirds of the medial accessory olive, in the dorsal cap, and in the ventral lateral outgrowth. Such neurons were extremely rare in the cat; only a few were found in the rostral parts of the principal olive, the medial accessory olive, and the dorsal accessory olive. In the rhesus monkey, the principal olive and the lateral region of the rostral medial accessory olive contained most of the intranuclear GABAergic neurons, but some were also present in the dorsal accessory olive. In the human, such neurons occurred in the principal olive, the dorsal accessory olive and the rostral medial accessory olive, but as in the rhesus monkey, most were observed in the principal olive. © 1992 Wiley‐Liss, Inc.