摘要:

AbstractThe organization of thalamic input to functionally characterized zones in primary somatosensory cerebral cortex (S‐I) of macaque monkeys (Macaca mulatta) was investigated using the method of labelling by retrograde transport of horseradish peroxidase (HRP). It was found that the cell columns positioned at the posterior margin of the band of cortex representing a given body region receive thalamic input from a posterior level of the ventroposterior thalamic nucleus (VP), and that cell columns at successively more anterior positions within that band receive input from successively more anterior levels of VP. The extreme posterior and anterior margins of the S‐I hand, foot and face areas receive input from neuron populations which are not as widely separated in the anteroposterior dimension of VP as the neurons projecting to the extreme anterior and posterior margins of the proximal limb and trunk representations in S‐I. These characteristics of the organization of the projections from VP to S‐I are consistent with the view that the body representations in VP and S‐I have the same connectivity and differential submodality distribution; and with the idea that thalamocortical connections only exist between functionally equivalent neuron populations in V

ISSN:0092-7317    

DOI:10.1002/cne.901780302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractAnterior dorsal ventricular ridge (ADVR) is a major telencephalic structure in reptiles. The intrinsic, efferent, and afferent connections of ADVR were studied in water snakes (Natrix sipedon) and garter snakes (Thamnophis sirtalis) using orthograde degeneration and Golgi techniques.ADVR in these snakes contains four zones oriented concentric with the ventricular surface and named zones A, B, C, and D, with zone A being the most peripheral. Each zone contains a characteristic population of neurons. Zone A neurons have dendrites which extend obliquely through zone A and into zone B. Zone B neurons have dendrites with a high density of dendritic spines and axons which ramify in zone A concentric with the ventricle, typically bearing large varicosities about 5 μ in length. Zone C neurons have dendrites with a low density of dendritic spines and axons which ramify within about 300 μ of the soma, typically bearing small varicosities about 3 μ in length. Zone D neurons resemble those in zone C, except that their axons may course ventrally out of ADVR into the subjacent striatum.Lesions placed superficially in ADVR produce terminal degeneration which is restricted to ADVR in Fink‐Heimer preparations. Lesions which damage the ventral part of ADVR produce degeneration in striatal nuclei (medial striatal nucleus, intrapeduncular nucleus, and perifascicular complex) as well as in the ventral two‐thirds of the posterior dorsal ventricular ridge. Unilateral transections of the midbrain produce degeneration in a system of thick caliber axons, with thin collaterals, which enters ADVR caudally behind the anterior commissure and rostrally through the lateral forebrain bundle. These fibers are oriented primarily along the radii of ADVR and confined predominantly to zones B, C, and D. Lesions of the dorsal thalamus produce degeneration in a system of thin caliber axons which enters ADVR rostrally through the lateral forebrain bundle. These fibers course radially through zones C and D and then turn to run concentric with the ventricle in zone B.These observations suggest that snake ADVR consists of two fundamentally different parts. Neurons in zones A and B interact strongly with neighboring neurons through somatosomatic and axodendritic contacts and participate in connections which run concentric with the ventricle. Neurons in zones C and D participate in connections which run radially. Some of the neurons in zone D, and possibly some in zone C, project to the striatum. Neurons situated near the ventral border of ADVR are the only source of ADVR efferents. Neurons in each zone interact with those in neighboring

ISSN:0092-7317    

DOI:10.1002/cne.901780303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe morphological and behavioral effects of complete binocular deprivation were studied by rearing cats from birth in total darkness. Nineteen animals were sacrificed immediately upon removal from the dark at intervals that ranged from 3 to 16 weeks. Measurements of cell sizes in the dorsal lateral geniculate nucleus revealed that dark rearing affects cell growth in two stages. During the first three months of dark rearing the growth rate of geniculate cells is reduced, and a maximum size difference between cells from light reared control animals and dark reared cats is seen at 12 weeks. However, during the fourth month of deprivation, geniculate cells recover from the effects of dark rearing, and grow to essentially normal size by 16 weeks.In a separate set of experiments, cats were removed from the dark at 8, 12 and 16 weeks, and given normal visual experience for as long as one and one‐half years. Lateral geniculate neurons in these animals were also normal in size.These results indicate that the effects of dark rearing on cell growth in the lateral geniculate nucleus are significant, but transitory, since they can be reversed either by long term deprivation, alone, or by exposure to normal levels of illumination.Behavioral experiments were performed to study the influence of dark rearing upon visually guided avoidance, jumping, placing, and following. After 8, 12 and 16 weeks of dark rearing, cats appear blind when first examined, and fail each of the behavioral tests. Within four weeks, however, visuomotor behavior recovers almost completely.Visual field perimetry testing was also carried out, and the results indicate that orientation is not reliably affected by periods of dark rearing less than 12 weeks in duration. However, 16 week dark reared animals show visual field defects, which persist for several months, and suggest that only the nasal hemiretina is used for orientation. Since the dark reared cats which showed deficits in orientation also demonstrated a pronounced convergent strabismus, it is proposed that misalignment of the visual axes may be directly responsible for the behavioral impairmen

ISSN:0092-7317    

DOI:10.1002/cne.901780304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe postnatal development of cytoplasmic laminated bodies in lamina A cells of the lateral geniculate nucleus in normal and dark reared cats has been studied quantitatively with light microscopy. In the normal cat laminated bodies develop between the sixth and eighth postnatal week and increase steadily in number thereafter. These inclusion bodies are found chiefly in medium size cells and are distributed more densely in the medial part of lamina A than laterally. Laminated bodies appear not to be a general feature of the visual pathways since they are not found in cells of the visual cortex, superior colliculus, or ventral lateral geniculate. In the dark reared cat laminated bodies develop at about the same time as in the normal animal, but approximately twice as many of them are seen at all ages investigated.Our experiments indicate that dark rearing does not cause a proliferation of multiple laminated bodies within single neurons, but rather induces the formation of a laminated body in cells that normally would not acquire one. This effect appears to be permanent since it is not reversed by long term dark rearing nor by periods of normal visual experience following deprivation.Physiological experiments (Sherman et al., '72) have shown that fewer Y‐cells are recorded in binocularly deprived cats than in normally reared animals. On the basis of the present results, it is suggested that dark rearing influences the functional specificity of developing lateral geniculate neurons. In this view, deprivation prevents normal numbers of Y‐cells from developing. Neurons which would have become Y‐cells develop instead as X‐cells; a change in functional organization which is associated structurally with an increase in the number of cells that contain cytoplasmic laminated

ISSN:0092-7317    

DOI:10.1002/cne.901780305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractAlthough the cat's canine tooth has become the accepted model for the electrophysiological study of dental sensory mechanisms no examination of its innervation has been carried out at the electron‐microscopical level. This study looked at the number and size distribution of both myelinated and non‐my‐elinated fibers in the crown of the cat's canine. The material examined was prepared by routine methods and the measurements taken from electron‐microscopical montages of pulpal cross‐sections. The measurements were made using a Quantimet 720 image analysis system. In one complete cross‐section 3,470 fibers were counted. Eighty‐one percent of these were non‐myelinated with a modal diameter of 0.35 μm. The modal diameter of the myelinated fibers was 2.5 μm. The relative preponderance of non‐myelinated fibers increased from core to periphery. The largest myelinated fibers were concentrated in the core. The fiber size distribution was similar in the single complete and two partial sections examined. It is concluded that all the fibers in the crown of the cat's canine would be contained in the A‐delta and C groups and that the strikingly large number of fibers present suggests that the peripheral pulp has a dense innervation, many of the cell processes found there b

ISSN:0092-7317    

DOI:10.1002/cne.901780306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe cerebellofugal projections in the contralateral ascending pathway of the brachium conjunctivum (B.C.) in the rat have been investigated in 23 animals using the Fink‐Heimer technique to demonstrate the axonal degeneration resulting from complete B.C. lesions (7), partial B.C. lesions (14) and control lesions dorsal to the B.C. (2). All of the degeneration resulting from the concomitant involvement of the structures surrounding the B.C. is accounted for in terms of known fiber pathways and from the results in the control experiments.The contralateral ascending pathway ascends rostrally from the decussation of the B.C. through the ventromedial midbrain tegmentum to the diencephalon. In the midbrain, cerebellofugal fibers terminate heavily throughout the red nucleus including the nucleus minimus, while others pass dorsolaterally and dorsomedially from the ascending tract to terminate in adjacent midbrain nuclei. The dorsolaterally directed fibers terminate in the midbrain reticular formation, the stratum griseum profundum of the superior colliculus, the anterior pretectal nucleus and the nucleus of the posterior commissure; the dorsomedially directed fibers terminate in the principal oculomotor nucleus, the nucleus of Dark‐schewitsch, interstitial nucleus of Cajal and the central gray matter. A considerable number of the cerebellofugal fibers proceed more rostrally within the prerubral field and enter the thalamus by two routes. Most follow a direct subthalamic course within field H of Forel and after contributing fibers to the zona incerta, enter the caudal pole of the ventromedial nucleus (Vm) of the thalamus to terminate throughout Vm and the ventrolateral complex (Vl). Others enter via the internal medullary lamina and terminate throughout the parafascicular and central lateral nuclei. A small number of cerebellothalamic fibers form a commissural projection to Vl on the opposite side.The finding that the cerebellothalamic projections to the ventral nucleus are distributed throughout Vm and Vl establishes the Vm‐Vl complex as the homologue in the rat of the ventral anterior and ventral lateral nuclei in the primate tha

ISSN:0092-7317    

DOI:10.1002/cne.901780307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe cerebellofugal projections in the ipsilateral and contralateral descending pathways of the brachium conjunctivum (B.C.) in the rat have been investigated in 22 animals using the Fink‐Heimer technique to demonstrate the axonal degeneration resulting from complete B.C. lesions (6), partial B.C. lesions (14) and control lesions dorsal to the B.C. (2). The incidental degeneration resulting from the concomitant involvement of the structures surrounding the B.C. is accounted for in terms of known fiber pathways and from the results in the control experiments.This study confirms Ramón y Cajal's ('03) original observation that cerebellofugal fibers in the B.C. project caudally throughout the length of the hindbrain via both ipsilateral and contralateral descending pathways. The fibers forming theipsilateral descending pathwayproceed ventrally from the B.C. at the level of the trigeminal motor nucleus, turn caudally and terminate within nucleus reticularis parvocellularis (Rpa). In particular, fibers within this pathway terminate densely in two cytoarchitecturally distinct Rpa subnuclei – nucleus “k” (Meessen and Olszewski, '49) and a caudal linear subnucleus – which project to the cerebellum (Faull, '77). Thecontralateral descending pathway(B.C.de) proceeds caudally from the decussation of the B.C. within the ventromedial region of the magnocellular nuclei of the reticular formation of the pons and medulla. Cerebellofugal fibers of the B.C.de terminate in a distinctive pattern within precerebellar brainstem nuclei: densely throughout the middle third of nucleus reticularis tegmenti pontis; in a longitudinal zone of each of the three pontine gray subnuclei; in the principal and dorsal accessory nuclei of the inferior olive; and sparsely within nucleus reticularis paramedianus. Fibers in the B.C.de also terminate within the magnocellular nuclei of the reticular formation, principally the nuclei reticularis pontis oralis an

ISSN:0092-7317    

DOI:10.1002/cne.901780308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractUtilizing the centrifugal neuronal transport of intracellularly injected horseradish peroxidase (HRP), we have performed a light microscopic (LM) investigation of the intramedullary parts of the axons and axon collaterals of sciatic α‐motoneurons in the adult cat.The intramedullary parts of the α‐motor axons had comparatively short internodes (down to 75 μm) and were thinner than reported in earlier studies on the ventral root. Positive correlations were obtained when relating nodal diameters (2.8–7.8 μm) or the mean diameters of the motor axons in the white matter (4.4–9.0 μm) to the diameters of the initial axonal segments (2.3–4.9 μm).Eighty percent of the motor axons gave off one to five collaterals. There was no correlation between the numbers of collaterals and the lengths of the parent motor axons in the gray matter. The branching patterns of the axon collaterals showed considerable variation and the number of end branches from a single collateral ranged between 1 and 39. The rostro‐caudal distribution of the collateral end branches was arranged symmetrically within a narrow space (± 300 μm) around the origins of the first order collaterals.Outbulgings of the motor axon collaterals, interpreted as synaptic terminals, were found along (59%) or at the ends (41%) of the collateral branches, and were located 200–700 μm away from the origin of the first order collateral. No characteristic LM feature of the outbulg

ISSN:0092-7317    

DOI:10.1002/cne.901780309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractFollowing olfactory bulb removal in young and adult rats, many neurons in the primary olfactory cortex become markedly argyrophilic in silver impregnated preparations. Although argyrophilic neurons are found scattered throughout the pyramidal and multiform cell layers, the heaviest concentration is seen in the superficial part of the pyramidal layer.Electron microscopic analysis reveals that argyrophilic neurons are undergoing rapid degeneration. The degenerative changes are similar in all affected cells, although some cells begin to disintegrate within 24 hours following bulbectomy, whereas others are just beginning to show pathological changes at three or four days. The first clear signs of cellular degeneration occur in the cytoplasm of the perikaryon and involve swelling of mitochondria and polysome disaggregation. An increase in the electron density of the cytoplasm follows and this is accompanied by the appearance of enlarged cisternae and disruption of the nuclear membrane. Degenerative changes in the nucleus usually are detected at a slightly later stage than in the cytoplasm. Nuclear changes are characterized by the proliferation of local aggregations of condensed chromatin, and the replacement of the nucleolus with large homogenous islands of electron dense material. In advanced stages of degeneration ribosomes are increased in density and become uniformly dispersed throughout the cytoplasm. Remnants of necrotic organelles are visible only at the cellular periphery, and phagocytosis of dying neurons by astrocytes and microglia follows quickly.Evidence from HRP‐studies indicates that cells in the olfactory cortex, which project directly to the bulb do not correspond to those which show fulminant necrosis following olfactory bulb removal. The majority of those which degenerate are located superficially, whereas the cells of origin of the centrifugal projection lie more deeply. Based on this dissociation, it is proposed that rapid cell death in the olfactory cortex is not caused by retrograde factors involving axotomy, but is due instead to transneuronal deafferentation that results from a sudden massive loss of input from the olfactory bul

ISSN:0092-7317    

DOI:10.1002/cne.901780310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901780301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY