bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thalamic connections with limbic cortex. II. Corticothalamic projections
Authors: Kaitz Suzan S. , Robertson Richard T. 
Published: January 2005

AbstractThe corticothalamic projections from the cat limbic cortex have been investigated with anterograde and retrograde axonal transport techniques. Five limbic cortical areas—the anterior limbic area, the cingular area, the granular and dysgranular retrosplenial areas, and the presubiculum—were identified on the basis of their cytoarchitecture. Emphasis was placed on determining the laminar distribution of the cells of origin of the efferent projections, the projection pathways, and the sites of termination within the thalamus.Projections to the thalamus originate in layers V and VI of limbic cortex. In the cingular region the cells of origin are predominantly in layer V and to a lesser extent in layer VI, while the majority of cells projecting from the more caudal retrosplenial areas and presubiculum are in layer VI. There are two fiber pathways from each cortical area to the thalamus. One system of fibers passes through the internal capsule and lateral thalamic peduncle, and a second system travels in the cingulate fasciculus before piercing the corpus callosum to join the postcommissural fornix.The lateral dorsal nucleus and the anterior nuclear group, including the anterior dorsal, anterior ventral, and anterior medial nuclei, are the major thalamic recipients of projections from limbic cortex. Corticothalamic projections also terminate sparsely in the midline and intralaminar nuclear complex, including the central lateral, central dorsal, paracentral, central medial, rhomboid, and reuniens nuclei. Projections from the anterior limbic area project predominantly to the anterior medial, centrall lateral, and paracentral nuclei. The anterior ventral nucleus, anterior medial nucleus, and lateral dorsal nucleus are the major thalamic recipients of projections from the cingular area, the granular and dysgranular retro‐splenial areas, and the presubiculum. It appears that the anterior dorsal nucleus receives afferents only from the dysgranular retrosplenial area. Bilateral corticothalamic projections were found in the anterior medial, dorsal medial, central lateral, central medial, paracentral, and reuniens nuclei.
Cytoarchitecture of primitive brains: Golgi studies in flatworms
Authors: Keenan C. Larry , Coss Richard , Koopowitz Harold 
Published: January 2005

AbstractNotoplana acticola, a free‐living polyclad flatworm, has a small but well‐defined brain that controls behavior of peripherally based motoneurones. This is the most primitive brain currently being studied electrophysiologically, but little is known of its cytoarchitecture. Using a modified rapid Golgi method, we have investigated neurone configurations within this brain. Superficially the brain resembles those of other invertebrates, but its cells also possess many vertebrate features. There is a surprising diversity of cell types with complicated branching patterns. Multipolar neurones appear to be the most common type. A few typical invertebrate monopolar cells were also stained. Bipolar cells occur in the rind. Processes resembling dendritic spines were observed. Measurements of these indicate that they fall within the range found in other vertebrates and invertebrates. Small multipolar cells that could either be glial or interneurones were found scattered through the brain.
Reciprocity of receptive field images and point images in the superior colliculus of the cat
Authors: Capuano Umberto , McIlwain James T. 
Published: January 2005

AbstractThe largest receptive fields mapped during microelectrode penetrations through the upper strata of the cat's superior colliculus vary substantially in size and shape in different collicular regions. Previous work has shown that when these large fields are plotted in the retinotopic map of the colliculus, their profiles become elliptical and vary little in size and orientation over the central regions of the map. Such profiles are called the receptive field images (RFIs) in the visual coordinate system of the colliculus. Of particular interest here is the relationship of these RFIs to the region of the colliculus occupied by cells whose receptive fields include a common visual point. We call this region the point image in the colliculus. A straightforward geometric argument indicates that the point image in the upper collicular strata should have the same size, shape, and orientation as the RFIs of the large‐field cells recorded here, if, indeed, these RFIs are translationally invariant as suggested by the earlier studies.The experiments reported here directly assessed the translational invariance of large‐field RFIs in the superior colliculi of individual cats. The results support the previous inference that the profiles are oval with their long axes oriented mediolaterally. The mediolateral and anteroposterior dimensions of the profiles were about 2.7 and 2.0 mm, respectively, wherever they were measured in the central regions of the colliculus. Since the boundaries of the point images in the superficial strata must have similar shape and dimensions, these data indicate that a visual point is “seen” by collicular cells spread through a substantial fraction of the tissue recieving the projection of the contralateral visual field.
The representation of the auditory and somatosensory systems in the external nucleus of the cat inferior colliculus
Authors: Aitkin L. M. , Kenyon C. E. , Philpott P. 
Published: January 2005

AbstractParallel single unit and retrograde tracing experiments were carried out in the anesthetized cat to elucidate the representation of the auditory and somatosensory systems in the external nucleus of the inferior colliculus (ICX).Units responding to tonal stimuli were more commonly encountered in ICX and the adjacent intercollicular area (ICA) than were units with identified tactile receptive fields. Concomitantly, a larger number of retrogradely labeled cells were identified in midbrain auditory structures, following injections of horseradish peroxidase (HRP) into ICX, than were found in the combined dorsal column nuclei.Microelectrode recording revealed that the entire accessible body surface was represented in ICX, and receptive fields of individual units were usually large and mostly located on the contralateral side. HRP‐labeled cells were scattered throughout the contralateral cuneate, gracile, and spinal trigeminal nuclei. tations of tone pips. Responses to complex sound were commonly observed. Binaural stimuli influenced the firing of the majority of auditory units. Labeled auditory neurons following ICX injections were found mainly in the inferior colliculus of both sides. Spread of tracer into the central and pericentral nuclei was associated with labeling of many neurons in hind brain auditory structures.Only vague suggestions of somatotopy or tonotopy were observed in the electrophysiological experiments; similarly, no topographical relationship between HRP injection site and locus of retrograde label in a given projecting nucleus could be discerned.Speculations were made, in the light of the dual convergent sensory representation in ICX, about the role of this structure in acoustico‐motor mechanisms.
The time of origin of neurons in the hippocampal region of the rhesus monkey
Authors: Rakic P. , Nowakowski R. S. 
Published: January 2005

AbstractThe time of origin of neurons in the hippocampal region was determined in a series of rhesus monkeys, each of which had been exposed to a pulse of tritiated thymidine (3H‐TdR) at a different time during ontogeny and sacrificed between the second and fifth month after birth. No heavily labeled cells were found in the hippocampal region of animals exposed to 3H‐TdR before embryonic day 33 (E33). Exposure to 3H‐TdR given at E36 labels a few neurons in the deepest layers of the entorhinal area, and 3H‐TdR given at E38 labels a small number of neurons in all hippocampal subdivisions. Although the first neurons are generated almost simultaneously throughout the hippocampal region, the proliferation ceases at a different time in each subdivision. The last neurons destined for the entorhinal area and presubiculum are generated between E70 and E75, whereas the last parasubicular neurons are generated between E75 and E80. The production of neurons that form the subiculum ends about two weeks earlier, between E56 and E65. Within the hippocampus, genesis of pyramidal cells ends between E70 and E80 in area CA1, between E56 and E65 in area CA2, between E65 and E70 in area CA3, and between E75 and E80 in area CA4. In contrast, the genesis of granule cells of the fascia dentata is considerably prolonged. It continues throughout the second half of gestation, declines steadily in the course of the first postnatal month, and tapers off during the next 2 months.There is a distinct inside‐to‐outside spatiotemporal gradient in the parahippocampal formation and in the stratum pyramidale of both the subiculum and hippocampus. In contrast, the spatiotemporal pattern of granule cell origin in the dentate gyrus is outside‐to‐inside. Furthermore, granule cells generated between E36 and E80 are distributed in a distinct suprapyramidal‐to‐infrapyramidal gradient, whereas those generated at later ages are distributed evenly throughout the fascia dentata. Correlation of the present findings with histological data on hippocampal neurogenesis in the human brain demonstrates that the timing and sequence of developmental events as well as spatiotemporal gradients are similar in both primate species.
The site of origin and route and rate of migration of neurons to the hippocampal region of the rhesus monkey
Authors: Nowakowski R. S. , Rakic P. 
Published: January 2005

AbstractThe site of origin and route and rate of migration of neurons in the developing hippocampal region of the rhesus monkey were studied with tritiated thymidine (3H‐TdR) autoratiography. Analysis of specimens sacrificed approximately 1 hour after exposure to 3H‐TdR shows that the neurons destined for the hippocampus and subiculum are generated exclusively in the ventricular zone lining the medial wall of the lateral cerebral ventricle. In contrast, neurons of the parahippocampal formation are generated in two proliferative zones: The majority of neurons destined for the lamina principalis interna arise from the ventricular zone, whereas most of those destined for the lamina principalis externa originate from the subventricular zone. The neurons of the dentate gyrus are also generated in two locations: in the ventricular zone (between E38 and E85) and within the prospective hilus of the dentate gyrus (from E58 up to approximately 3 months after birth).Analysis of specimens sacrificed at progressively longer intervals after exposure to 3H‐TdR indicates that neurons destined for all of the subdivisions of the hippocampal region (except those cells generated in the hilus of the dentate gyrus) migrate through the intermediate zone, bypassing previously generated neurons on their way to the superficial limits of the developing cortical plate. Estimated migration rates are approximately 15 μm/day in the sector of the hippocampal formation, about 100 μm/day in the parahippocampal formation, and about 115 μm/day in the region of adjacent neocortex. Thus simultaneously generated neurons destined for three distinct cytoarchitectonic areas have significantly different rates of cell migration. These differences are unrelated to the length of cell trajectories and may depend on the mechanism of cell translocation and/or the timing of signals that initiate cell movement. The differential rate of migration indicates that the fate of postmitotic cells may be determined before they have reached their final destination.
The topography of primate retina: A study of the human, bushbaby, and new‐ and old‐world monkeys
Authors: Stone Jonathan , Johnston Elizabeth 
Published: January 2005

AbstractThe distribution of ganglion cells has been studied in the retinas of four primates: the prosimian bushbaby, the New‐World squirrel monkey, the Old‐World crab‐eating cynamolgous monkey, and the human. The sizes of ganglion cell somas were also measured at a number of retinal locations and compared with similar measurements in the cat retina to test for the presence in primates of retinal specializations such as the visual streak, and for gradients in retinal structure, such as that between temporal and nasal retina.In all four primates, ganglion cell somas in peripheral retina ranged considerably in diameter (6–16 μm in the bushbaby, 8–22 μm in the squirrel monkey, 8–23 μm in the cynamolgous monkey, 8–26 μm in the human). It seems likely that the strong physiological correlates of soma size which have been described among cat retinal ganglion cells and among the relay cells of the macaque lateral geniculate nucleus are generally present in primates. In all four primates, evidence was also obtained of a visual streak specialization; the isodensity lines in ganglion cell density maps were horizontally elongated, and small‐bodied ganglion cells were relatively more common in the region of the proposed streak than in other areas of peripheral retina. However, the visual streak seems less well developed than in the cat; among the four primate species examined it was best developed in the bushbaby, at least as assessed by the shape of the isodensity lines.All four primates showed a clear foveal specialization, but this feature seemed least developed in the bushbaby. At the fovea, ganglion cells are smaller in soma size than in peripheral retina; they also seemed more uniform in size, although some distinctly larger cells persist in the human and bushbaby. Soma size measurements also provided evidence of a difference between nasal and temporal areas of peripheral retina comparable to that reported for the cat and other species.Thus the primate retinas examined show features, such as the foveal specialization, which seem unique to them among mammals. They also show features, such as nasal‐temporal differences in ganglion cell size, and (though weakly developed) a visual streak, which they have in common with other mammals with widely different phylogenetic histories.
Collateral sprouting of insect motorneurons
Authors: Donaldson P. Lynn , Josephson Robert K. 
Published: January 2005

AbstractThe metathoracic extensor tibiae muscle of the cricket, Teleogryllus oceanicus, is innervated by two excitatory axons: a fast axon, which initiates large twitches to single stimuli, and a slow axon, which evokes minute twitches to single stimuli, but which, through facilitation and summation, evokes readily measurable tension to repetitive stimulation. The fast axon and the slow axon leave the metathoracic ganglia in different nerve roots, the fast axon through nerve 5 and the slow axon through nerve 3. The fast axon innervates muscle fibers in the middle of the extensor tibiae, and the slow axon innervates muscle fibers at the proximal and distal ends of the muscle. A central region of muscle fibers is innervated by only the fast axon. This region is flanked on either side by dually innervated fibers, fibers that receive both the fast and the slow axons. Fibers with only slow axon innervation are restricted to a wedge‐shaped patch in the proximal extensor tibiae and a larger region in the most distal portion of the muscle. Sectioning nerve 5 containing the fast axon, or nerve 3 containing the slow axon, partially denervates the extensor tibiae. Functional transmission by the fast axon fails 7–10 days after nerve section. The innervation field of the intact motorneuron expands in a partially denervated muscle. The linear expansion rate of the slow axon field is about 20–40 μm per day. The enlarged slow field does not regress when axons regenerate to the muscle through nerve 5. The progressive expansion of the slow innervation field suggests that the expansion is due to collateral sprouting of slow axon terminals.
Studies on the somatotopy of the trigeminal system in the mallard, Anas platyrhynchos L. III. Afferents and organization of the nucleus basalis
Authors: Dubbeldam Jacob L. , Brauch Christiane S. M. , Don Anneke 
Published: January 2005

AbstractThe ascending projections from the principal sensory nuclues V (PrV) have been studied by tracing degeneration after lesions in the PrV and by injections of HRP into the projection zone of PrV. The quintofrontal tract arises from PrV, ascends into the forebrain, and terminates in the ipsilateral and the contralateral nucleus basalis (NB). The contralateral fibers decussate in the the tegmentum at the level of the trochlear‐oculomotor nuclei. NB is a laminar nucleus lying over the rostral part of the paleostriatal complex. Dorsally NB is bounded by the neostratum. NB consists of small neurons. In the dorsal part of NB, these neurons are arranged in vertical columns; the afferents ascend through these columns, and clusters of degenerated boutons are found around the cells. It is possible to distinguish regions in NB receiving ophthalmic, maxillary, mandibular, or glossopharyngeal afferents. The rostral part of NB receives an exclusive ipsilateral projection; the intermediate part, a bilateral projection; and the caudal part, a contralateral projection, with the exception of the most caudal area, which also receives a bilateral projection. It is not clear whether NB should be considered a thalamic, a telencephalic, or even a pallial structure. The hypothesis that the columnar organization of the NB is a prerequisite to preserve a precise somatotopy of the tactile system of the oral region is discussed. In this respect the organization of NB can be compared to that of layer IV of the somatosensory (SI) cortex of mammals. Knowledge of the structure and functions of the peripheral tactile sense system opens the possibility of subdividing the NB into functional units.
Primary afferent axons in the tract of lissauer in the monkey
Authors: Coggeshall Richard E. , Chung Kyungsoon , Chung Jin Mo , Langford Lauren A. 
Published: January 2005

AbstractThe main thrust of the present study was to determine the numbers of primary afferent fibers in the tract of Lissauer in the monkey. The findings are that approximately 40% of the axons in the tract of Lissauer are primary afferent axons from a single segment, and approximately another 40% are primary afferents from segments cranial and caudal to the segment under consideration. Presumably, the remaining 20% are propriospinal axons. There is relatively little difference in the proportions of primary afferents in medial as opposed to lateral parts of the tract, and in this respect the monkey differs somewhat from the rat and cat. Thus in the monkey the tract of Lissauer should probably be regarded as a primary afferent pathway with the propriospinal fibers forming a distinct but relatively minor component of the tract.
Organization of extrinsic tectal connections in goldfish (Carassius auratus)
Authors: Grover B. G. , Sharma S. C. 
Published: January 2005

AbstractNonretinal sources of tectal afferents, the laminar and regional organization of the inputs, and the relation of the tectum with primary and secondary visual and motor centers in goldfish were studied following HRP injections in the optic tectum, orbit of the eye, cerebellum, pretectal area, and dorsolateral mesencephalic tegmentum.Ipsilateral tectal afferents include the area dorsalis centralis of the forebrain, the nucleus dorsalis lateralis of the thalamus, the area pretectalis, the nucleus pretectalis, a nucleus in the rostral mesencephalic tegmentum, the torus longitudinales, the torus semicircularis, a dorsolateral tegmental nucleus, the nucleus isthmi, and a rostral cell group of the nucleus motorius tegmenti.Comparison of results in a series of tectal HRP injections which differed in depth, tangential extent, and location indicated that projections from the area pretectalis, nucleus pretectalis, and nucleus isthmi terminate in the stratum fibrosum et griseum superficiale of the tectum. Terminals of the forebrain and nucleus dorsolateralis and contralateral tectum are sparse and widely branching. Projections from the area and nucleus pretectalis tend to terminate in the rostral tectum, and those from the contralateral tectum, torus semicircularis, dorsolateral tegmental nucleus, and nucleus motorius tegmenti terminate preferentially in the caudal tectum.Cells of origin of extrinsic tectal efferents were also identified following HRP injections in the pretectal area and mesencephalic tegmentum. Proximal dendrites and axons of these cells were labeled sufficiently to allow comparison with morphological types characterized in Golgi studies.HRP injections in the cerebellum labeled cells bodies in the area pretectalis, nucleus pretectalis, and the nucleus of the posterior commissure. Double label experiments with intraocular injection of tritiated proline demonstrated direct retinal input to these three areas. No indications of direct connections between the tectum and cerebellum were found following tectal or cerebellar HRP injections.
The aberrant retino‐retinal projection during optic nerve regeneration in the frog. I. Time course of formation and cells of origin
Authors: Bohn Ronald C. , Stelzner Dennis J. 
Published: January 2005

AbstractWe have reported previously that during optic nerve regeneration in Rana pipiens, axons are misrouted into the opposite nerve and retina. In the present investigation we have examined the time course of formation of these “misrouted” axons and their cells of origin. The right eye of 31 frogs was injected with 3H‐proline at various times after right optic nerve crush. In every frog examined 2 weeks and later after nerve crush, the distribution of autoradiographic label indicated that axons from the right eye had grown into the left optic nerve at the chiasm. The amount of label increased from 2 weeks to reach a maximum at 6 weeks where the entire left nerve was filled with silver grains. At 5 to 6 weeks after crush, laboled axons were found within the ganglion cell fiber layer (GCFL) of the retina of the opposite eye for a maximum distance of 2.3 mm from the optic disc. In frogs examined at intervals later than 6 weeks after crush, the amount of label within the left eye and nerve progressively decreased, indicating a gradual disappearance of the misrouted axons. Studies using anterograde transport of horseradish peroxidase (HRP) after nerve injection confirmed these autoradiographic findings. The position of ganglion cells in the right eye whose axons were misrouted to the left eye was determined by retrograde transport of HRP. Five or 6 weeks after crushing the right optic nerve, the left eye was injected with HRP and labled ganglion cells were found throughout the right eye retina. The largest percentage of labeled cells was found within the ventral half of the retina, particularly within the temporal quadrant, and nearly all of the labeled cells were found in more peripheral portions of the retina. Since few retino‐retinal axons are found during normal development, the present results show that the factors guiding regenerating axons in the adult frog differ substantially from those present during development.