bluuebunny/crossref_metadata_2025_split huggingface dataset:
Areal differences in the laminar distribution of thalamic afferents in cortical fields of the insular, parietal and temporal regions of primates
Authors: Jones E. G. , Burton H. 
Published: January 2005

AbstractA cytoarchitectonic parcellation has been made of the cortex of the insula and of the adjoining parts of the temporal and parietal lobes in rhesus and squirrel monkeys. In conjunction with this, the intracortical distribution of the thalamo‐cortical fibers has been studied by the autoradiographic tracing technique.There is a systematic change in the density, laminar distribution and general character of the intracortical thalamic afferent plexus which seems to follow, in particular, the progressive differentiation of cortical layering that occurs in moving from insular through granular to homotypical cortex. In the dysgranular and granular insular areas in which cortical lamination is indistinct, the thalamic plexus as demonstrated autoradiographically is sparse and extends through much of layers III and IV. In the granular cortex (areas 3b and AI), the thalamic plexus is densest and coarsest; it fills all of layers IV and IIIB and extends into layer IIIA. In the “second” and “third” sensory areas, such as the second somatic sensory and many of the auditory fields, the density of the plexus and its coarseness diminish slightly and the deeper half of layer IV becomes free of terminals. In the homotypical cortex, the plexus becomes sparser, finer and strictly confined to layer IIIB. In many areas there are additional indications of thalamic terminations in deeper layers. Where layers V and VI are not divided into sublaminae (e.g., in areas 3b and AI) there is labeling of the superficial half of layer VI. Where layers V and VI become subdivided in the homotypical cortex, the labeling is confined to layer VB. Terminations in layer I of the cortex of the auditory and adjacent fields were only observed in cases in which the magnocellular nucleus of the medial geniculate body was involved by the injection of isotope.The boundaries of the cortical projection fields of individual thalamic nuclei, as determined autoradiographically, are remarkably sharp and invariably coincide with a sharp architectonic boundary or with a zone of maximal cytoarchitectonic change. Zones of apparent architectonic transition never showed overlap of thalamic afferents emanating from more than one nucleus.These results raise for discussion the significance of architectonic structure in relation to cortical connectivity and have a bearing upon those studies that have attempted to relate the terminals of thalamic afferents to particular classes of cortical neuron.
The posterior thalamic region and its cortical projection in new world and old world monkeys
Authors: Burton H. , Jones E. G. 
Published: January 2005

AbstractThe posterior nuclear complex of the thalamus in rhesus, pigtailed and squirrel monkeys consists of the combined suprageniculate‐limitans nucleus and an ill defined region of heterogeneous cell types extending anteriorly from the dorsal lobe of the medial geniculate body towards the posterior pole of the ventral nuclear complex. This region is referred to as the posterior nucleus.The cortical projections of each of these nuclei, together with those of the adjacent ventral, pulvinar and medial geniculate complexes, have been studied by means of the autoradiographic tracing technique. The suprageniculate‐limitans nucleus, the main input to which is the superior colliculus, projects upon the granular insular area of the cortex. The medial portion of the posterior nucleus projects to the retroinsular field lying posterior to the second somatic sensory area. There is clinical and electrophysiological evidence to suggest that the retroinsular area may form part of a central pain pathway. The lateral portion of the posterior nucleus which is closely related to certain elements of the medial geniculate complex, projects to the postaditory cortical field. The ventroposterioinferior nucleus, which may be involved in vestibular function, projects to the dysgranular insular field.The principal medial geniculate nucleus can be subdivided into a ventral division that projects to field AI of the auditory cortex and a dorsal division that merges with the posterior nucleus; it is further subdivided into an anterodorsal component that projects to two fields on the superior temporal gyrus, together with a posterodorsal component in which separate cell populations project to areas lying anterior and medial to AI. The magnocellular medial geniculate nucleus, sometimes considered a part of the posterior complex, appears to project diffusely to layer I of all the auditory fields.The Auditory fields are bounded on three sides by the projection field of the medial nucleus of the pulvinar which also extends into the upper end of the lateral sulcus to bound the fields receiving fibers from the posterior nucleus. The topography of the areas receiving fibers from the posterior, medial geniculate and pulvinar complexes, taken in conjunction with the rotation of the primate temporal lobe, permits all of these fields to be compared with similar, better known areas in the cat brain.
Light and electron microscopy of the ground squirrel retina: Functional considerations
Authors: West Roger W. 
Published: January 2005

AbstractLight and electron microscopy of Golgi‐impregnated ground squirrel retinas have revealed a range of morphological subtypes of bipolar, amacrine, and ganglion cells. There are at least seven subtypes of bipolar cells. Those subtypes in which the somata were high (sclerad) in the inner nuclear layer (3 subtypes) had axon terminals low (vitread) in the inner plexiform layer, and those with somata low in the inner nuclear layer (4 subtypes) had axon terminals high in the inner plexiform layer. The bipolar subtypes with high axon terminals made flat contacts with receptor cells, whereas all but one of the bipolar subtypes with low axon terminals made ribbon‐related contacts with receptor cells. There are at least five subtypes of amacrine cells. The two subtypes which the Golgi method revealed most frequently were a broad‐field, unistratified neuron with a dendritic spread in excess of 1,000 m̈m and a narrow‐field, diffuse neuron with a dendritic spread of about 30 m̈m. The broad‐field, unistratified cell had the lowest proportion of amacrine vs. bipolar cell synaptic input of the amacrine subtypes (43%), whereas the narrow‐field, diffuse cell had one of the greatest proportions of amacrine cell input (96%). There are at least 15 subtypes of ganglion cells. The proportion of synaptic inputs to these cells ranged from 21% to 100% amacrine cell synapses. An attempt has been made to relate this new knowledge of retinal circuitry to the physiological output of the ganglion cells.
Alterations in receptive field properties of superior colliculus cells produced by visual cortex ablation in infant and adult cats
Authors: Mize R. Ranney , Murphy E. H. 
Published: January 2005

AbstractTo determine if functional alterations in the superior colliculus might account for recovery of visual behaviors following visual cortex removal in infant cats, the receptive field characteristics of single units in the superior colliculus of cats whose visual cortex was removed within the first week of life were compared with those of cats which sustained visual cortex lesions in adulthood and with those of normal cats. In the normal superior colliculus, 90% of all cells responded to moving stimuli irrespective of shape or orientation. Sixty‐four percent of these units were directionally selective, responding well to movement in one direction but poorly or not at all to movement in the opposite direction. Ninety percent of units were binocular, the vast majority of these responding equally to stimulation of either eye or showing only slight preference for stimulation of the contralateral eye. Responses to stationary flashes of light were observed in only 33% of all visually activated cells in the normal superior colliculus. After visual cortex ablation in adult cats, only six percent of movement sensitive cells were directionally selective. Binocular preference was shifted following adult visual cortex lesions such that sixty percent of all cells responded exclusively or predominantly to stimulation of the contralateral eye. Seventy‐one percent of all visually responsive units responded to stationary lights flashed on or off within their receptive field boundaries. Lesions limited primarily to area 17 had the same effect as larger lesions of visual cortex. Infant visual cortex lesions resulted in receptive field alterations similar to those observed after adult ablation. Only fifteen percent of motion sensitive units were directionally selective. Seventy‐one percent responded exclusively or predominantly to stimulation of the contralateral eye. Seventy‐six percent of visually responsive cells were activated by stationary light. Lesions largely confined to area 17 produced the same alterations as more extensive lesions of visual cortex. Thus, no evidence was found that the superior colliculus is involved in the functional reorganization presumed to occur following visual cortex ablation in infant cats. Recovery of visual behaviors following neonatal injury may therefore not involve alterations in the receptive fields of single cells.
Synapse formation in the mouse olfactory bulb. II. Morphogenesis
Authors: Hinds James W. , Hinds Patricia L. 
Published: January 2005

AbstractSerial thin sections of the mouse olfactory bulb from the fourteenth day of gestation (E14) to postnatal day 44 (P44) have been examined in order to study morphogenesis of individual synaptic junctions. At the initiation of synapse formation structures are found that resemble postsynaptic densities but are facing extracellular space or unmodified processes. Transition forms between these isolated postsynaptic densities and undoubted synapses have been found. These observations as well as quantitative studies support the hypothesis that isolated postsynaptic densities can form independently and be converted to synapses when a presynaptic specialization develops opposite them.Detailed studies of olfactory axodendritic synaptogenesis throughout the entire developmental period suggests strongly that these asymmetrical synapses pass through an immature symmetrical phase: (1) symmetrical olfactory axodendritic synapses are found in significantly higher concentration on axonal and dendritic growth cones than on more mature processes; (2) the number of symmetrical synapses is correlated with the rate of formation of new synapses determined previously. The time for a recognizable symmetrical synapse to be transformed into a recognizable asymmetrical one has been calculated to be 9–10 hours.A scheme of synapse formation in the CNS has been proposed in which a postsynaptic structure forms independently followed by aggregation of pre‐existing presynaptic components into a presynaptic specialization. Different morphogenetic sequences of synapse formation from region to region are attributed simply to different relative rates in the development of the postsynaptic density and the presynaptic specialization.
Axonal guidance of developing optic nerves in the frog. I. Anatomy of the projection from transplanted eye primordia
Authors: Constantine‐Paton M. , Capranica Robert R. 
Published: January 2005

AbstractRight or left eye primordia of Shumway stage 16–18 Rana pipiens embryos were transplanted to the position normally occupied by the ear, where they developed into externally normal eyes.Ganglion cell density in the retina of the transplanted eye was significantly lower than the ganglion cell density in the animal's normal eyes. No significant difference was observed between normal and transplanted inner and outer nuclear layers.In several preparations a large piece of embryonic forebrain was included in the initial eye graft. Optic nerves from the transplanted eyes penetrated this transplanted forebrain and established a dorsocaudal growth trajectory relative to the ectopic tissue's original anterior‐posterior and dorsal‐ventral axes. After traversing the forebrain, the transplanted optic nerve fibers penetrated the medulla where they invariably grew dorsocaudally to take up and maintain a dorsolateral position in the white matter of the spinal cord.The consistent dorsocaudal trajectory established by the translocated optic tract in the ectopic forebrain and in the hindbrain and spinal cord is very similar to the growth trajectory in the normal diencephalon, suggesting that dorsocaudal growth relative to the three major axes of the neural tube is an inherent property of optic nerve fibers. These results also suggest that the polarity cues which guide normal optic tract growth are not unique to the diencephalic regions of the neural tube.
Origins of axons in the cat's acoustic striae determined by injection of horseradish peroxidase into severed tracts
Authors: Adams Joe C. , Warr W. Bruce 
Published: January 2005

AbstractOrigins and terminations of fibers of the dorsal and intermediate acoustic striae were studied by surgically severing these tracts and injecting HRP into the incision. This procedure results in filling the severed axons with HRP. Filled axons were traced to cell groups of origin and to some terminations of the acoustic striae. HRP‐labeled terminals were found in the cochlear nuclei as well as in periolivary cell groups. Filling of cells with HRP ranged from being complete, resulting in Golgi‐like images, to being barely detectable. Labeled cells were abundant in the dorsal and posteroventral cochlear nucleus adjacent to the injection as well as scatered throughout the periolivary cell groups of both sides, being highest in concentration around the ipsilateral lateral superior olive. On the side contralateral to the injection, labeled cells were found along the medial border of the dorsal cochlear nucleus, in the interstitial nucleus of the stria of Held, and sparsely throughout the ventral cochlear nucleus. The distribution of labeled cells was similar following HRP injections of the dorsal cochlear nucleus, except that these injections revealed additional descending projections from the inferior colliculi and from the ventral nucleus of the trapezoid body of both sides. These additional projections were interpreted as entering the CN by a ventral route. Findings of this study are in accord with physiological recordings made from fibers of the acoustic striae.
Recovery from the effects of monocular deprivation in kittens
Authors: Mitchell Donald E. , Cynader Max , Anthony Movshon J. 
Published: January 2005

AbstractSignificant recovery from the effects of early unilateral eye closure has been found following a period of reversed deprivation involving forced usage of the deprived eye. A simple period of binocular vision, however, has been reported to be ineffective. We have compared these two recovery conditions (reversed deprivation and binocular vision) in kittens initially deprived to the age of 45 or 60 days, and given seven to eight weeks of recovery. We estimated behavioral recovery by measuring visual acuity through the deprived eye. Kittens deprived to day 45 attained nearly normal grating resolution in their deprived eyes (5–6 cycles/degree), while those deprived to day 60 showed enduring partial acuity deficits (4–5 cycles/degree). Surprisingly, the deprived eye's acuity in kittens given binocular vision during recovery was nearly the same as that possessed by the deprived eyes of reverse‐deprived kittens. We estimated physiological recovery from the visual response properties and eye dominance of 359 cortical neurons; all kittens showed shifts in eye dominance from the situation that obtains after a period of deprivation. Reverse‐deprived kittens, in agreement with previous reports, showed more pronounced shifts of cortical eye dominance than did binocularly recovered kittens. Nevertheless, significant recovery of both the deprived eye's influence and of the selectivity of its receptive fields was seen in kittens given binocular vision. In no case was there significant recovery of cortical binocular interaction: most neurons were monocularly driven, and were aggregated into ocular dominance columns strongly dominated by one eye or the other. Since both behavioral and electrophysiological measurements suggest considerable recovery of function even in cases where kittens were merely given binocular vision during recovery, we conclude that the two eyes'effectiveness is not solely determined by competitive interaction – significant changes can occur when neither eye has a competitive advantage over the other.
Cytoarchitectonic analysis of the bullfrog (Rana catesbeiana) spinal cord by means of electron microscopy with special reference to distribution of microneurons
Authors: Sasaki Hiroshi 
Published: January 2005

AbstractIn order to determine cytological nature of the “small cells” found in the dorsal half of the bullfrog spinal cord at the electron microscopic level, the complete mapping of these elements was carried out, using both paraffin and thick sections. Asa result, these elements were demonstrated to have four main fine structural characteristics of an unequivocally neuronal nature: (1) synaptic contacts, (2) subsurface cisternae, (3) typical pattern of the rough‐surfaced endoplasmic reticulum, and (4) close contacts of astroglial proc‐esses with the somal surface.The most prominent features in the bullfrog spinal cord can be summarized as follows: the microneurons occupy the dorsal region as well as the region around the central canal of the gray, and the most dorsal part of the gray in exclusively occupied by these microneurons. They show, furthermore, a tendency to separate grossly into medial and lateral groups. No microneurons are visible in the ventral horn. According to the results obtained from the cytoarchitectonic com‐parison of the bullfrog spinal cord and the rat spinal cord, it can be said that in the former no differentiated laminar structures can be recognized, while in the latter the gray matter is sufficiently differentiated to permit full percellation.
An electron microscope observation of the right and the two left portions of the habenular nuclei of the frog
Authors: Kemali Milena , Guglielmotti Vittorio 
Published: January 2005

AbstractThe right dorsal habenula (RDH), the left dorsal habenula, lateral portion(LDH‐LP) and the left dorsal habenula, medial portion (LDH‐MP) of the adult frog Rana esculenta have been studied by the electron microscope with the use of three types of fixatives: osmium tetroxide, aldehydes and potassium permanganate.The study has demonstrated in the habenulae of both sides a variety of synaptic vesicles, special synaptic patterns (en passant, serial, axo‐somatic) containing small spherical transparent vesicles, never mixed with other types of vesicles, and large pale processes containing big granules. However, a particular type of synaptic vesicles characterized by small clear spherical vesicles with a tiny dark granule revealed by potassium permanganate fixation has been demonstrated only in the neuropil of the LDH and not in the RDH. Further, a peculiar type of intracytoplasmic inclusion appears in the form of myelin‐like and crystal‐like formations only in the LDH‐MP.On the basis of these consistent ultrastructural differences, the dorsal habenular nuclei of the frog can be considered as composed of three individual nuclei, each with its own morphological characterization, dislocated, for some unknown reason, one on the right and two on the left side of the epithalamus.The results suggest that the LDH‐MP is a nucleus metabolically different from the others and that the projections to the dorsal habenular nuclei are different on the right and left sides of the brain.
Neurophysiology of spastic, a behavior mutant of the mexican axolotl: Altered vestibular projection to cerebellar auricle and area acoustico‐lateralis
Authors: Ide Charles F. 
Published: January 2005

AbstractThe spastic mutant of Ambystoma mexicanum shows deficiencies in swimming coordination and equilibrium. Behavior “phenocopy” experiments done previously indicated that vestibular projections to cerebellum and hindbrain interneurons might be responsible for mutant behavior patterns. To test function in mutant vestibular projections, single unit recordings were carried out in the vestibulo‐cerebellum (auricle) and hindbrain area acousticolateralis (AAL) of wild‐type and mutant animals in response to natural vestibular stimulation. Vestibular unit types responding during longitudinal tilting or to sustained tilt were encountered in equal proportions in both animal types. However, mutants showed a significant increase in spontaneously active units in these areas indicating possible deficiencies in inhibitory circuitry. In addition, the topographic location of vestibular units changed under the influence of the spastic gene. In mutants, significant numbers of units were found “translocated” into a ventro‐caudal auricular zone abutting the AAL. Anatomical studies detailed in the following paper have shown this same area to contain grossly “translocated” cerebellar cells and afferent fiber tracts in mutants. These data are drawn together in a model in which deficiencies in the (form and) inhibitory function of the vestibulo‐cerebellum is postulated to underly the behavioral abnormalities of the spastic phenotype.
The cytoarchitecture of the torus semicircularis in the Tegu lizard, Tupinambis nigropunctatus
Authors: Browner Robert H. , Rubinson Kalman 
Published: January 2005

AbstractThe torus semicircularis (TS) of the Tegu lizard extends from the superficial caudal mesencephalon, dorsal to the exiting trochlear nerve, to a position ventral to the middle part of the optic tectum and its ventricle. It has an oblique orientation with the caudal pole abutting the midline while the rostral end is lateral and slightly ventral. The TS consists of a central nucleus and several adjacent cell groups. The central nucleus and the laminar nucleus, situated medially, extend the entire length of the TS while the cortical nucleus, situated dorsally and laterally, is present only in the caudal superficial portion. The central nucleus is composed of ovoid neurons with branched, radiating dendrites. The dendrites are directed medially and laterally with spines on the distal portion of the dendritic tree. The laminar nucleus consists of three to five neuronal layers. It is mainly composed of fusiform neurons with one dendritic trunk from each extremity of the soma. There is little branching and few dendritic spines.The cortical nucleus is a laminated region consisting of alternating layers of neurons and lateral lemniscal fibers. The neurons of the superficial layers are fusiform with their long axis perpendicular to the long axis of the brainstem. They possess two main dendritic trunks which parallel the laminae and are covered with dendritic spines. The deeper layers consist of pyramidal neurons with three dendritic trunks, secondary branches, and few spines. The long axis of these neurons extends from the center of the TS to the periphery. Two dendritic trunks extend dorsally or laterally towards the surface, while the third extends towards the central nucleus. The dendrites, thus, extend across the laminae. In addition, a cell‐free lateral zone is described.