摘要:

AbstractTo investigate the afferent projections to the flocculus in a nonhuman primate, we injected horseradish peroxidase into one flocculus of six rhesus macaques (Macaca mulatta) and processed their brains according to the tetramethylbenzidine protocol to reveal retrogradely labeled neurons. Labeled neurons were found in a large set of nuclei within the rostral medulla and the pons.The greatest numbers of labeled neurons were in the vestibular complex and the nucleus prepositus hypoglossi. There were neurons labeled bilaterally throughout all the vestibular nuclei except the lateral vestibular nucleus, but most of the labeled neurons were in the caudal parts of the medial and inferior vestibular nuclei and in the central part of the superior vestibular nucleus; the nucleus prepositus was also labeled bilaterally, primarily caudally. Modest numbers of labeled neurons were found in the y‐group, most ipsilaterally, and many neurons were labeled in the interstitial nucleus of the vestibular nerve. No labeled neurons were found in the vestibular ganglion following a large injection into the flocculus.A second large source of afferents to the flocculus was the medial, paramedial, and raphe reticular formation. Dense aggregates of labeled neurons were located in several pararaphe nuclei of the rostral medulla and the rostral pons and in the nucleus reticularis paramedianus of the medulla and several component nuclei of the nucleus reticularis tegmenti pontis bilaterally. Several groups of cells within and abutting upon the medial and rostral aspects of the abducens nucleus were labeled bilaterally.There was a modest projection from two parts of the pontine nuclei. Both a dorsal midline nucleus ventral to the nucleus reticularis tegmenti pontis and a collection of nuclei in a laminar region adjacent to the contralateral middle cerebellar peduncle contained labeled neurons whose numbers, while modest, were large compared to the projections to the flocculus in other animals. This generic difference may be due to the greater development of the smooth pursuit system in monkeys and the consequent need for a more substantial input from the cerebral cortex.As in other genera, the inferior olive projected to the flocculus via the dorsal cap of Kooy and the contiguous ventrolateral outgrowth. The projection was completely crossed and large injections labeled virtually every neuron in the dorsal cap, suggesting that the dorsal cap is the principal source of climbing fiber afferents.A comparison of these afferent sources to the monkey flocculus with the discharge patterns of floccular mossy fibers suggests that certain afferent projections may provide particular subsets of mossy fibers. Consistent with its suggested role in the genesis and modification of slow eye movements, the flocculus receives information from structures whose neurons discharge with head and eye movements. However, the floccular projections from the stomatosensory nuclei, the nucleus ceruleus, and the raphe nuclei suggest that the flocculus may participate in a larger repertoire of behaviors than just smooth eye movement

ISSN:0092-7317    

DOI:10.1002/cne.902350102

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

年代:1985

数据来源: WILEY

摘要:

AbstractTo fulfill its putative role in short‐ and long‐term modification of the vestibulo‐ocular reflex, the flocculus of the cerebellum must send efferents to brainstem nuclei involved in the control of eye movements. In order to reveal the sites of these interactions, we determined the projections of the flocculus by autoradiography and orthograde transport of horseradish peroxidase in five rhesus macaques.Anterogradely labeled axons collected at the base of the injected folia and coursed caudally and medially between the middle cerebellar peduncle and the flocculus. They swept medially over the caudal surface of the middle cerebellar peduncle, over the dorsal surface of the cochlear nuclei, and then caudally along the lateral surface of the inferior cerebellar peduncle to pass over its dorsal surface in the cerebellopontine angle and terminate exclusively in the ipsilateral vestibular nuclei.Three contingents of axons could be differentiated. The axons of one group flowed caudally and medially into the y‐group, which clearly received the densest floccular projection. Other, notably thicker, axons of this group continued rostrally and medially to terminate chiefly in the large‐cell core of the superior vestibular nucleus. A second large contingent of thin axons streamed caudal and ventral to the y‐group to form a compact tract adjacent to the lateral angle of the fourth ventricle and dorsal to the medial vestibular nucleus. Fibers from this tract (the angular bundle of Löwy) supplied a sizable projection to the rostral part of the medial vestibular nucleus and modest projection to the ventrolateral vestibular nucleus. A final group of fibers extended caudally and medially from the y‐group in a plexus ventral to the dentate and interposed nuclei to terminate in the basal interstitial nucleus of the cerebellum (Langer, '85), a broadly distributed cerebellar nucleus on the roof of the fourth ventricle.The flocculus can affect vestibulo‐ocular behavior only through these efferents to the vestibular nuclei and the basal interstitial nucleus o

ISSN:0092-7317    

DOI:10.1002/cne.902350103

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

年代:1985

数据来源: WILEY

摘要:

AbstractWe have shown that the monkey flocculus is not connected with any of the major, well‐demarcated cerebellar nuclei. There is, however, a broadly distributed interstitial population of neurons in the white matter ventral to the cerebellar nuclei and extending into the peduncle of the flocculus; this population, previously undescribed in the monkey, has reciprocal connections with the flocculus (Langer et al., '85a,b). Several lines of evidence indicate that this collection of neurons, called the basal interstitial nucleus of the cerebellum (BIN/Cb), can justifiably be considered a nucleus.(1) Injection of horseradish peroxidase (HRP) into the flocculus always labels a group of neurons that lie immediately ventral to the well‐demarcated cerebellar nuclei and extend posteromedially into the lateral margin of the nodulus and rostrolaterally around the caudal surface of the y‐group, infiltrating the peduncle of the flocculus.(2) In Nissl‐stained material there is a readily seen collection of neurons that are clearly distinct from the overlying cerebellar nuclei, with precisely the same distribution. These neurons have a characteristic morphology: they are intermediate‐sized, chromatophilic, multipolar, and fusiform, and have rapidly tapering proximal dendrites. The cell nucleus is generally placed eccentrically in the cell body, against the plasma membrane or in one pole of the cell. The Nissl substance is usually finely granular in the center of the cell body and forms dense clumps adjacent to the cell membrane.(3) Anterograde label from injections of HRP or tritiated amino acids into the flocculus extends over the same group of neurons.In one brain with an HRP injection involving a part of the BIN/Cb there was a patchy, clustered distribution of labeled Purkinje cells extending throughout the flocculus and into the adjacent lateral parts of the simple lobule. The clusters were confined to the medial half of many of the floccu

ISSN:0092-7317    

DOI:10.1002/cne.902350104

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe ultrastructural features of murine vallate taste bud cells and their associated synapses have been examined in thin and thick sections with conventional transmission electron microscopy and high‐voltage electron microscopy. Computer‐assisted reconstructions from serial sections were utilized to aid in visualization of taste bud cell‐nerve fiber synapses.We have classified taste bud cells on the basis of previously established criteria‐namely, size of the nucleus, shape and density of chromatin, density of cytoplasm, and presence or absence of dense‐cored or clear vesicles, other cytoplasmic organelles, and synaptic foci. Both dark cells and light cells are present, as well as cells with intermediate morphological characteristics.Synapses were observed from taste bud cells onto nerve fiber processes. In virtually all instances, synapses are associated with the nuclear region of the taste cell. These synapses are characterized by the presence of 40–70 nm clear vesicles embedded in a thickened presynaptic membrane separated from the postsynaptic membrane by a 16–30 nm cleft. Synapses are not unique to any particular cell type. Dark, intermediate, and light cells all synapse onto nerve fibers. Two general types of synapses exist: spot (or macular) and fingerlike. In the latter, the postsynaptic region of the neuronal process protrudes into an invagination of the taste cell membrane. Differences in synaptic morphology are not correlated with taste cell type. In some cases a single taste cell was observed to possess both macular and fingerlike synapses adjacent to one another, forming a synaptic complex onto a single neuronal process. On the basis of the presence of synaptic contacts, we conclude that both “dark” and “light” cells ar

ISSN:0092-7317    

DOI:10.1002/cne.902350105

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

年代:1985

数据来源: WILEY

摘要:

AbstractThis article is an application of light and electron microscopic immunocytochemistry to the study of the neuronal circuit of the superficial layers in the rat dorsal cochlear nucleus (DCN). An antiserum against the intrinsic marker glutamate decarboxylase (GAD) is used to identify and map axon terminals and neurons that use gamma aminobutyric acid (GABA) as a neurotransmitter. It is demonstrated that layers 1 and 2 of the DCN contain a very high density of GABAergic boutons, matched only by the granule cell domains of the ventral cochlear nucleus, especially the superficial granule cell domain. These two layers also contain much higher concentrations of GABAergic cell bodies than all other magnocellular regions of the cochlear nuclear complex. Cartwheel and stellate neurons, and probably also Golgi cells, previously characterized in Golgi and electron microscopic investigations, appear immunostained and, therefore, are presumably inhibitory. The synaptic relations between parallel fibers, the axons of granule cells, and cartwheel and stellate neurons are confirmed. The present study also supports the conclusion that stellate cells are coupled to one another by gap junctions. Also scattered in layer 1 are large, GABAergic neurons that occur with irregular frequency and presumably represent displaced Purkinje cells, previously identified with a Purkinje‐cell‐specific marker. Granule neurons and pyramidal neurons remain unstained, even after topical injection of colchicine, which enhances immunostaining of the other glutamate‐decarboxylase‐positive cells, and therefore must use transmitters different from GABA.The possible analogies between the spiny cartwheel and the aspiny stellate cells of the DCN and the cerebellar Purkinje and stellate/basket cells are discussed in the light of data from Golgi, electon microscopy, and transmitter imunocytoch

ISSN:0092-7317    

DOI:10.1002/cne.902350106

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe prenatal and early postnatal neurogenesis of the human climbing fibers of the lateral cerebellar hemispheres have been studied, with the rapid Golgi method, and correlated with the developmental stages of Purkinje cells. A transitional phase has been established in the neurogenesis of the human Purkinje cell between the second and third stages of Cajal. This phase coincides with the arrival of the climbing fibers. It is characterized by the reabsorption and subsequent transformation of Purkinje cell's basal dendrites into somatic spines. Following the arrival of the climbing fibers and the establishment of contacts, the Purkinje cell is progressively transformed from an immature stellate and nonoriented cell into a monopolar and spatially oriented one which acquires all of its mature morphological and functional features.The human climbing fibers arrive at the Purkinje cell plate by the 28th week of gestation and establish a transient paraganglionic plexus before contacts with these neurons can be recognized. They start to form pericellular nests by the 29th week, and by the 31st week of gestation all Purkinje cells of the lateral hemispheres have pericellular nests around their bodies. These pericellular nests are progressively and rapidly transformed into supracellular “capuchones” which themselves are also short‐lived because the climbing process starts readily in them. Supracellular “capuchones” are recognized by the 34th seek and their fibrils start to climb the dendrites of Purkinje cells (young climbing phase) by the 36th week of gestation. The process of climbing the dendrites of the Purkinje cells will continue through late prenatal and early postnatal life.The human climbing fibers are distributed, in the internal granular layer, within narrow and long vertical territories which are transverse to the long axis of the follium. A single climbing fiber is (1) able to establish contacts with many Purkinje cells located within its narrow territory of distribution; (2) has a tendency to establish contacts with small groups of Purkinje cells rather than with isolate neurons; (3) able to send collaterals to several contiguous cerebellar folia; and (4) able to send collaterals to the internal granular layer and to form pericellular nests in it. The human cerebellum may be considered to be subdivided into a series of parallel, narrow, and transverse structural/functional planes, each one characterized by the distribution of a climbing fiber. It should be emphasized that the axonic collaterals of the Purkinje neurons are similarly distributed and oriented within the internal granular layer and could represent elements of the same flat functional planes. Observations made in this study suggest that the disappearance of the lamina dissecans may be, in part, related to the reabsorption of the Purkinje cell's basal dendrites and hence to the arrival of the climbi

ISSN:0092-7317    

DOI:10.1002/cne.902350107

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe large mystacial vibrissae on the faces of rodents have punctate representations in all stations in the central trigeminal pathway, including layer IV of the somatosensory cortex (SmI). The cortical whisker correlates, multicellular units termed barrels, are not present at birth, and damage to the vibrissae during the first postnatal week results in altered adult cytoarchitectonics The anatomical effects of vibrissae damage in the cortex have been well documented; here, we investigated the functional organization of altered SmI barrels with a high‐resolution 2‐deoxyglucose (2‐DG) technique (Durham et al., '81, J. Neurosci.1:519). The middle row of vibrissae was cauterized in 1‐, 2‐, 3‐, 4‐, or 5‐day‐old mice, and the animals were allowed to survive to sexual maturity. Various combinations of vibrissae were clipped acutely 24 hours prior to injection of 2–4 mCi of (3H)2‐DG. Mice actively explored an empty cage for 60 minutes, stimulating the remaining vibrissae. The mice then were perfused and their brains prepared for paraffin histology and emulsion autoradiography.In tangential sections through layer IV, patterns of neuropil and cell body labeling were analyzed with respect to barrel cytoarchitecture in normal and vibrissae‐damaged mice. In both control and experimental animals, patterns of neuropil and cell somata label corresponded exactly to barrel boundaries, whether normal or altered by vibrissae damage. Only those barrels for which vibrissae were intact had high levels of label, with anterior barrels more heavily labeled. Many neurons in the septa between these barrels and the adjacent barrels were labeled also. We found slightly higher neuropil label in the cortical zone corresponding to the damaged zone on the face in animals lesioned at any time. These data indicate that physiological somatotopy in vibrissae‐damaged animals matches the an

ISSN:0092-7317    

DOI:10.1002/cne.902350108

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

年代:1985

数据来源: WILEY

摘要:

AbstractInterhemispheric connections were studied in tree shrews (Tupaia belangeri) after multiple injections of horseradish peroxidase or horseradish peroxidase conjugated to wheat germ agglutinin into the cortex of one cerebral hemisphere. After an appropriate survival period, the areal pattern of connections was revealed by flattening the other hemisphere, cutting sections parallel to the cortical surface, and staining with tetramethylbenzidine. Architectonic boundaries were identified by using sections stained for myelinated fibers. Labeled cells and axon terminations formed largely overlapping distributions that covaried in density, although labeled cells appeared to be more evenly distributed than labeled terminations. Connections were concentrated along the border of area 17 (V‐I) with area 18 (V‐II). However, connections also extended as far as 2 mm into area 17 to include cortex representing parts of the visual field 10° or more from the zero vertical meridian. Clusters of dense connections spanned the width of area 18, where they alternated with regions of fewer connections. These clusters roughly corresponded in location to regions with heavier myelination. In the visually responsive temporal cortex, connections were also unevenly distributed. The organization of most of this cortex is not understood, but one subdivision, the temporal dorsal area (TD), has been identified on the basis of reciprocal connections with area 17. The central part of the TD had few interhemispheric connections, while most of the outer border had dense connections. The auditory cortex had dense and patchy connections throughout. The pattern in the primary somatosensory cortex (S‐I) varied according to the representation of body parts, so that the cortex related to the forepaw had sparse connections, while connections were dense but uneven over much of the representation of the face, nose, and mouth. A focus of connections was found at the border of the forepaw and face representations, where the myelination of S‐I cortex is interrupted. Dense, uneven connections also characterized the second somatosensory area, S‐II. The motor cortex was densely connected, with only slightly fewer terminations rostral to the forepaw region of S‐I. Other parts of frontal cortex had dense connections, The distribution of cortical connections varied with depth for at least some areas, so that clusters of cells and terminations were found in supragranular layers in S‐I, S‐II, and TD, while infragranular labeled cells were more evenly distributed.The results indicate that interhemispheric connections in tree shrews are widely distributed and include large portions of primary sensory fields, and that the primary somatic and visual areas have more interhemispheric connections than their homologues in higher primates. The local unevenness of the connections suggests that functions are unevenly distributed within cortical areas. Because visual and somatic areas representing the contralateral visual hemifield or body surface receive callosal inputs, many of these connections are not reflected in the excitatory receptive fields of

ISSN:0092-7317    

DOI:10.1002/cne.902350109

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

年代:1985

数据来源: WILEY

摘要:

AbstractTransganglionic and anterograde horseradish peroxidase transport was used to evaluate the central projections of undamaged trigeminal (V) nerve branches in adult rats and hamsters subjected to transection of the infraorbital nerve and to cauterization of the vibrissae follicles at birth. In rats, deafferented regions of the V brainstem nuclear complex did not receive abnormal projections from undamaged mandibular sensory afferents. Undamaged ophthalmic‐maxillary fibers also failed to terminate heavily in the region deafferented by the neonatal infraorbital lesions.In the hamster, on the other hand, neonatal infraorbital nerve lesions were associated with statistically significant increases in mandibular terminal fields in the principalis, subnucleus interpolaris, and subnucleus caudalis.Tracing experiments were also carried out in neonatal rats and hamsters to determine whether the above‐described differences in the response to infraorbirtal nerve damage reflected a difference in the maturity of the V primary afferent projections to the brainstem at the time of our neonatal lesions. In neonatal rats, the infraorbital and mandibular projections to the V brainstem nuclear complex were quite adultlike, both in their pattern and in the extent of their overlap, which was minimal. Overlap between mandibular and infraorbital terminal fields was also minimal in the newborn hamst

ISSN:0092-7317    

DOI:10.1002/cne.902350110

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

年代:1985

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902350101

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

年代:1985

数据来源: WILEY