摘要:

AbstractThe somatotopic organization of the postcentral parietal cortex of the Old World monkey,Macaca fascicularis, was determined with multi‐unit microelectrode recordings. The results lead to the following conclusions: (1) There are at least two complete and systematic representations of the contralateral body surface in the cortex of the postcentral gyrus. One representation is contained within Area 3b, the other within Area 1. (2) While there are important differences in the organization of the two representations, they are basically mirror‐images of each other. (3) Each representation maintains body‐surface adjacency by cortical adjacency in some mediolateral regions. In other regions, two types of discontinuities can be described: first, in which adjacent body surfaces are represented in separate cortical loci; second, in which adjacent cortical regions represent disparate body‐surface regions. The internal organization of each representation is better described as a composite of somatotopic regions (Merzenich et al., '78) than as a serial array of dermatomal bands, or as a “homunculus.” (4) While architectonic Area 2 responds to stimulation of deep body tissue, at least parts of Area 2 also respond to cutaneous stimulation. The organization of the cutaneous representation of the hand in Area 2 is basically a mirror‐image of the hand representation in Area 1. (5) Area 3a is activated by deep body tissue stimulation, suggesting the possibility of a fourth body representation within the traditional “S‐I” region of somatosensory cortex in macaques. In accord with a previous study in a New World monkey (Merzenich et al., '78), we suggest that the cutaneous representation in Area 3b be considered asSI proper, and that the cutaneous representation in Area 1 be termed theposterior cutaneous field. Furthermore, based on the orientation of the representations of the body surface, as well as other factors, we suggest that the representation in Area 3b is homologous to “SmI” (o

ISSN:0092-7317    

DOI:10.1002/cne.901920402

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe sensory innervation of primate sinus hairs has been studied by light and electron microscopy. For light microscopy paraffin sections as well as thick frozen sections were impregnated with silver and compared with serial semi‐thin sections of tissue prepared for electron microscopy. One type of sensory terminal is present in the epidermis surrounding the hair follicle, and four specific nerve terminals have been identified within the blood sinus. An epidermal rete ridge collar encircles the hair shaft and contains ∽200 Merkel cellneurite complexes. Numerous other Merkel cell‐neurite complexes are present in the external root sheath of the hair follicle beneath a thick glassy membrane innervated by ∽65 nerve fibers. At this level 10–15 lanceolate or palisade terminals are situated in the connective tissue. Up to 10 simple encapsulated corpuscles can be identified above the level of lanceolate endings and Merkel cell terminals. Ruffini corpuscles are closely applied to the glassy membrane below the lanceolate and Merkel terminals at the level where nerve fibers penetrate the capsule of the sinus. All of these terminals are supplied by 80–100 large diameter myelinated fibers distributed approximately as follows: 65 innervate Merkel cell‐neurite complexes, 15 to lanceolate, 10 to simple corpuscles, and 10 to Ruffini corpuscles. The innervation of the rete ridge collar is independent of that of the sinus consisting of 10–12 fibers derived from the superficial dermal network. Each of these sensory terminals can be correlated with specific functional parameters as described in numerous neurophysiologic studies. Merkel cell‐neurite complexes and Ruffini corpuscles are slowly adapting receptors; lanceolate terminals and simple corpuscles are rapidly a

ISSN:0092-7317    

DOI:10.1002/cne.901920403

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe organization of the Cebus monkey retina was analysed after the intraocular injection of 5,6‐dihydroxytryptamine. This amine was taken up not only by the previously known dopaminergic neurons, but also by a set of indoleamine‐accumulating neurons, whose processes are confined to the inner plexiform layer.The synaptic contacts of the dopaminergic neurons were analysed in the electron microscope after the processes of the indoleamine‐accumulating neurons were destroyed by the intrvitreal injection of the neurotoxic indoleamine, 5,7‐dihydroxytryptamine. The subsequent injection of 5,6‐dihydroxytryptamine induces certain changes in the dopaminergic neurons which accumulate the substance: electron‐dense cores appear in the synaptic vesicles, and increased electron‐density of mitochondrial and cellular membranes is often observed.The dopaminergic neurons were found to be presynaptic to amacrine cell perikarya and processes in the inner plexiform layer. In the outer plexiform layer they were presynaptic to both bipolar and horizontal cells, but they did not contact photoreceptors. The dopaminergic neurons received synapses only in the inner plexiform layer, from amacrine cell processes. It is inferred that in Cebus most dopaminergic neurons belong to a special class of retinal neuron, the interplexiform cells, which appear to transmit information centrifugally within the retina, from the inner to the outer plexiform layers. There are considerable similarities between the synaptology of the dopaminergic interplexiform neurons in the Cebus monkey and the goldfish retina, and the function of interplexiform neurons may therefore be similar in thes

ISSN:0092-7317    

DOI:10.1002/cne.901920404

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe cytoarchitecture of the cochlear nucleus in young adult albino rabbits (Cuniculus oryctologus) has been examined in Nissl‐ and Golgi‐impregnated material to compare rabbit cochlear nucleus with other mammalian species. Cochlear nucleus was subdivided into anteroventral (AVCN), posteroventral (PVCN), and dorsal (DCN) regions, as in other mammals. AVCN was characterized by bushy cells and stellate cells. The “bushy” dendritic trees of adjacent bushy cells often overlapped. PVCN was characterized by octopus, elongate, and stellate cells. The dendritic trees of adjacent octopus cells extended in a parallel array across the auditory nerve fibers. DCN had molecular, fusiform and polymorphic layers. The fusiform cell layer was especially prominent, with the fusiform cells appearing visually to be the organizing elements in DCN. The large cells in DCN were the fusiform and giant neurons; the medium cells were the stellate and elongate neurons; the small cells were the cartwheel, small stellate, and granule cells. The cochlear nucleus of rabbit is essentially similar in cytoarchitectural organization to other mammalian species which have been studied. The detailed morphology of the various cell types seen in Golgi preparations is quite similar to that of cat (Brawer et al., '74), although some differences d

ISSN:0092-7317    

DOI:10.1002/cne.901920405

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to investigate innervation of transplanted supernumerary hindlimbs in the frog (Xenopus laevis). Motoneurons innervating identified muscles in normal and supernumerary limbs were located by the method of retrograde transport of HRP after intramuscular injection. In the lumbar spinal cord of normalXenopus, motoneurons supplying medial hindlimb muscles, which are derived from the ventral muscle mass during development, are located at the medial end of the motor column; those innervating lateral, dorsallyderived muscles, lie at the lateral end of the motor column. In animals with supernumerary limbs, motoneurons supplying the transplant usually occupied the same mediolateral position as those supplying the same muscle in the normal limb. However, the rostrocaudal location of these motor pools exhibited greater flexibility. When the transplant was innervated by a rostral nerve of the lumbar plexus, motoneurons supplying gastrocnemius could be located in a region of the spinal cord whose motoneurons do not normally innervate this muscle. There is thus no rigid requirement that gastrocnemius motoneurons be located at specific segmental levels. Motoneurons supplying gastrocnemius in the normal limb on the experimental side showed normal rostrocaudal distributions, indicating little rearrangement of these motor pools. Dorsal root ganglion cells labeled after HRP injection could be concentrated in a ganglion which normally supplies little or no innervation to the injected muscle. The location of these cells confirmed the segmental source of sensory innervation of the extra limb; i.e., there was no stray innervation. Animals with supernumerary limbs exhibited little or no increase in the number of motoneurons on the extra limb side. In contrast, dorsal root ganglion cell populations exhibited a large increase on the experimental side.

ISSN:0092-7317    

DOI:10.1002/cne.901920406

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe cochlear nuclei of three burrowing snakes (Xenopeltis unicolor, Cylindrophis rufus, andEryx johni) and three non‐burrowing snakes (Epicrates cenchris, Natrix sipedon, andPituophis catenifer) were studied. The posterior branch of the statoacoustic nerve and its posterior ganglion were destroyed and the degenerated nerve fibers and terminals traced to primary cochlear nuclei in 13 specimens ofPituophis catenifer.All these snake species possess three primary and one secondary cochlear nuclei. The primary cochlear nuclei consist of a small nucleus angularis located at the cerebello‐medullary junction and a fairly large nucleus magnocellularis forming a dorsal cap over the cephalic end of the alar eminence. Nucleus magnocellularis may be subdivided into a medially placed group of rounder cells, nucleus magnocellularis medialis, and a laterally placed group of more ovate and paler‐staining cells, nucleus magnocellularis lateralis. A small but well‐defined secondary nucleus which showed no degenerated nerve terminals after nerve root section, nucleus laminaris, underlies the cephalic part of both nucleus magnocellularis medialis and nucleus magnocellularis lateralis.Larger and better‐developed cochlear nuclei were found in burrowing species than in non‐burrowing species of snakes. Of the three burrowing species studied,Xenopeltisshowed the greatest development of cochlear nuclei;Eryxcochlear nuclei were not quite as large but were better differentiated than inXenopeltis; andCylindrophiscochlear nuclei were fairly large but not as well developed nor as well differentiated as in eitherXenopeltisorEryx. The cochlear nuclei of the three non‐burrowing snakes,Epicrates, Natrix, andPituophis, Were not as large nor as well developed as those of the burrowing snakes.There is some, but not complete, correlation between cochlear development and papilla basilaris length and number of hair cells. Thus,XenopeltisandEryx, with well‐developed cochlear nuclei, have relatively long papillae basilares; but the boid,Epicrates, with less well‐developed cochlear nuclei, has a fairly well‐developed papilla basilaris.Cylindrophis, a burrowing species, shows only a moderate degree of cochlear nuclei, have relatively long papillae basilares; but the boid,Epicrates, with less well‐developed cochlear nuclei, has a fairly well‐developed papilla basilaris.Cylindrophis, a burrowing species, shows only a moderate degree of cochlear nuclei and papilla basilaris development. The non‐burrowers,NatrixandPituophis, have both small cochlear nuclei and relatively

ISSN:0092-7317    

DOI:10.1002/cne.901920407

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

年代:1980

数据来源: WILEY

摘要:

AbstractAbout one‐quarter of the neurons in the A‐laminae of the cat lateral geniculate selectively accumulate exogenous [3H]‐γ‐aminobutyric acid (GABA), its analog, [3H]‐2,4‐diaminobutyric acid (DABA), and the GABA agonist, [3H] muscimol. These neurons are small (12–18 μm diameter) and lack a laminar body, which suggests that they correspond to the class III cell identified in Golgi material. GABA and DABA are also accumulated by F‐terminals which are post‐synaptic to retinal terminals and presynaptic to relay cell dendrites. It is suggested that GABA may be the transmitter for these small neurons which appear to mediate by means of local circuits a feed‐forward inhibition

ISSN:0092-7317    

DOI:10.1002/cne.901920408

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe organization of the major efferents of the rat subthalamic nucleus (STN) was investigated using a fluorescent retrograde double‐labeling technique. Red fluorcrescent Evans Blue was injected into the globus pallidus and blue fluorescent DAPI‐Primuline was injected into the substantia nigra. After retrograde axonal transport many double‐labeled neurons were seen throughout the STN. Occasional double‐labeled cells were seen in the lateral hypothalamus just medial to the STN and in a thin lateral strip of neurons extending laterally from the STN. Evidence for a mediolateral topography in both the STN‐pallidal and STN‐nigral pathways was obtained.The STN contains few, if any, local interneurons. Cell counts revealed that at least 94% of, and possibly all, STN neurons send axon collaterals to both the globus pallidus and subst

ISSN:0092-7317    

DOI:10.1002/cne.901920409

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

年代:1980

数据来源: WILEY

摘要:

AbstractEarly stages in chick neurogenesis were investigated with tritiated thymidine (3H‐Tdr) autoradiography to determine the location and identity of the first neurons produced for the central nervous system. These cells have been shown to arise prior to neural tube closure (Sechrist, '75). Chicks were treated at selected intervals between 20 and 72 hours of incubation with3H‐Tdr in a modified pulse‐labeling technique, and terminated on the 18th day of embryonic development (E18), when neuronal types could be determined. Some of the earliest neurons start their final DNA synthesis before 20 hours of incubation (head process, Hamburger‐Hamilton stage 5). These are primarily medium‐sized cells of the reticular formation in the medulla and at the diencephalic‐mesencephalic junction, but also in the intermediate zone of the spinal cord. Motor neurons of the brainstem and spinal cord begin to appear next, after 26–28 hours incubation; the first sensory neurons arise after 32 hours. Other workers (Ramon y Cajal, '60; Tello, '23; Windle and Austin, '36) found that neurons of the reticular formation were the first to differentiate neurofibrils, during the latter part of E2, indicating that fibrillogenesis in these cells begins about 24 hours after the initial cessation of DN

ISSN:0092-7317    

DOI:10.1002/cne.901920410

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

年代:1980

数据来源: WILEY

摘要:

AbstractFine structural characteristics of synapses in the spiral organ of Corti were examined, with reference to differences between inner and outer haircell systems, and to location of neurons of origin of efferent axons. Surgical interruption of crossed olivocochlear bundle, of vestibular nerve, of facial nerve, and excision of superior cervical ganglia were used to determine the pathways of efferent axons. Interruption of the vestibular nerve near the brainstem results in degeneration of all efferent terminals on outer hair cells. Mid‐line lesions at, and caudal to, the facial colliculus result in degeneration of about half of these efferent terminals. Efferent synaptic bulbs to the inner hair‐cell system are small, of the order of one micron, and form type 2 junctions with afferent dendrites. They tend to have more large dense‐core vesicles (about 80 nm) than the large efferent terminals of the outer hair‐cell system, and appear to be the terminals of axons in the habenula perforata, which exhibit varicosities laden with large dense core vesicles. The varicosities are unaffected by excision of the superior cervical ganglia. So far as our material can reveal, it appears that the varicosities in the habenula perforata do not survive vestibular root interruption, nor do the efferent processes in the internal spiral bundle or at the base of inner hair cells. Most interestingly, the afferent processes of the inner hair‐cell system, as identified for example by their relation to pre‐synaptic bodies in the inner hair cells, are subject to a trans‐synaptic reaction after severance of the vestibular root. They undergo a dramatic cytological transformation, characterized by increase of volume, engorgement with microtubules, microfilaments, microvesicles of various sizes, and clusters of lysosomes. Thus, both the efferent and afferent terminals of the inner hair‐cell system show marked cytological differences from the corresponding terminals of the outer h

ISSN:0092-7317    

DOI:10.1002/cne.901920411

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

年代:1980

数据来源: WILEY