摘要:

AbstractThe location, topographic organization, and function of the middle temporal visual area (MT) in the macaque monkey was studied using anatomical and physiological techniques. MT is a small, elliptically shaped area on the posterior bank of the superior temporal sulcus which can be identified by its direct inputs from striate cortex and by its distinctive pattern of heavy myelination. Its average surface area is 33 mm2, which is less than 3% of the size of striate cortex. It contains a complete, topographically organized representation of the contralateral visual hemifield. There are substantial irregularities in the detailed pattern of topographic organization, however, and the representation is significantly more complex than that found for MT in other primates. Much of MT is devoted to the representation of central visual fields, with the emphasis on central vision being similar to that found in striate cortex.Electrophysiological recordings have confirmed previous reports of a high incidence of direction selective cells in MT. The transition in functional properties, from cells lacking direction selectivity outside MT to direction selective cells within, occurs over a distance of 0.1–0.2 mm or less along the lateral border of MT. Such a transition does not occur along the medial border, however, as the cortex medial to MT contains many cells with strong direction selectivity. Nevertheless, this region differs from MT in its myeloarchitecture, its lack of inputs from striate cortex, and the large size of its receptive fields. These results demonstrate the existence of three distinct visual areas on the posterior bank of the superior temporal sulcus which can be distinguished on the basis of both physiological and anatomical criteri

ISSN:0092-7317    

DOI:10.1002/cne.901990302

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe central projections of afferent fibers from the cornea, and the infraorbital, infratrochlear, frontal, lacrimal and auriculotemporal nerves were investigated by means of the transganglionic transport of horseradish peroxidase. Afferent projections to the dorsal horn of the medulla are organized along both the rostrocaudal axis and the ventrolateral to dorsomedial margin of the medullary dorsal horn. An inverted but discontinuous facial representation exists through the rostrocaudal axis of the dorsal horn of the medulla with perioral and nasal receptive fields innervated by the infraorbital and infratrochlear nerves represented rostral to the progressively more posterior receptive fields innervated by the frontal, lacrimal and auriculotemporal nerves, respectively. The organization of the primary afferents is not uniform over the laminae of the dorsal horn of the medulla; the projections from the different nerves show the least overlap in lamina II, while overlap is most extensive in laminae I and V. The sensory projection from the cornea to the medullary dorsal horn is most dense in laminae I and II.All nerves, including those innervating the cornea, project to the interpolar, oral and principal trigeminal nuclei and are somatotopically organized. Projections to the reticular formation and the contralateral trigeminal sensory complex were not found in this study.These results support the organization of the dorsal horn of the medulla proposed by Déjerine (1914) and show that this organization is most evident for the primary afferent projections to lamina II

ISSN:0092-7317    

DOI:10.1002/cne.901990303

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe intracortical arborizations of neurons from the ventroposterolateral thalamic nucleus (VPL) in the cat were studied by intraaxonal injections of horseradish peroxidase (HRP) following identification of their receptive fields. In the primary somatic sensory cortex (SI) VPL cells terminated in different cytoarchitectonic areas according to their receptive field modality. Fibers excited by deep tissues or joint rotation arborized preferentially in area 3a. Those responding tonically to cutaneous stimuli were located in the anterior part of area 3b; hairdriven cells terminated in area 3b and in the rostral pole of area 1. All fibers had a similar laminar distribution within SI. Axons terminated mostly in layers VI, IV, and the lower part of layer III. None terminated in layers I and II. Most terminal arbors were oriented along the mediolateral axis of the brain. The main arborization of a single VPL cell formed a bush of about 500 μm in diameter. Some fibers generated two such bushes with an uninvaded region of about 300 μm between them. It is proposed that this patchy organization underlies in part the columnar organization of area SI. Many VPL cells had secondary projection sites in SI. These were issued from smaller‐sized collaterals and were located in a different cytoarchitectonic area than that of the main terminal plexuses. A significant number of these collaterals projected to area 4. Insufficient filling of the collaterals by HRP prevented a more complete characterization of the secondary arb

ISSN:0092-7317    

DOI:10.1002/cne.901990304

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

年代:1981

数据来源: WILEY

摘要:

AbstractIn rabbit retina, neurofibrillar methods stain two populations of amacrines whose cell bodies are located on either side of the inner plexiform layer: on in the ganglion cell layer and the other at the inner margin of the inner nuclear layer. The stained amacrines in the ganglion cell layer have the distinctive cytology of ‘coronate’ amacrines described from Nissl‐stained retina (Vaney, 1980a) and account for about 85% of the displaced amacrines in the rabbit retina. The coronate amacrines have a streak topography similar to that of the ganglion cells; they comprise about 32% of the neurons in the ganglion cell layer although their proportion increases with eccentricity from the visual streak. The cytology of the neurofibrillar stained amacrines in the inner nuclear layer resembles that of the displaced amacrines and their densities are almost equal. The cell bodies of the stained amacrines are smaller than those of the displaced amacrines but larger than most others in the inner nuclear layer; they account for some 2% of the neurons in the amacrine sublayer. Although the cell bodies of both populations are distributed rather evenly, the mosaic of the inner nuclear layer cells is more regular than that of the ganglion layer cells. We propose that the two populations of amacrines stained by neurofibrillar methods correspond to the acetylcholine synthesizing cells labelled by Masland and Mills (

ISSN:0092-7317    

DOI:10.1002/cne.901990305

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe superficial layers of the viper optic tectum, which receive fibers from the retina, were studied using both light and electron microscopes. The optic fibers layer, orstratum opticum, is composed of 200 to 250 tight fascicles containing thin fibers, nearly all of which are myelinated. In the main optic terminal layers, thestratum griseum et fibrosum superficiale, the greatest part of the cellular population is composed of small vertically oriented neurons and horizontal nerve cells, many of which are probably local circuit neurons.The neuropil of thestratum griseum et fibrosum superficialeis made up of small nerve elements, including three types of profiles containing synaptic vesicles: (1) boutons with pleiomorphic synaptic vesicles (P), representing over 47% of the total population of profiles containing synaptic vesicles and comprising three subgroups (P1, P2, and P3); (2) boutons with spheroidal synaptic vesicles (S), forming more than 29% of the total population of profiles containing synaptic vesicles and comprising two categories, S1and S2(S2, the more numerous, represents the optic boutons, which make up 22% of the total population of profiles containing synaptic vesicles); and (3) dendrites with pleiomorphic vesicles, accounting for approximately 23% of the total population of profiles containing synaptic vesicles. A study of synaptic patterns revealed a large number of serial synapses and a lesser number of triplets or triadic synapses. The presynaptic components are boutons containing spheroidal (S1, S2) or pleiomorphic (P1, P2, P3) synaptic vesicles. The intermediate profile was always a dendrite with synaptic vesicles which frequently belonged to the small neurons of thestratum griseum et fibrosum superficiale. Comparison of the present results with other recent data shows that the synaptic circuitry in the optic tectum ofVipera aspisclosely resembles the pattern observed in the optic tectum of other vertebrates, ranging from fish to mammals. However, quantitative differences exist, especially with regard to the proportion of dendrites containing synaptic vesicles. Their number seems to be higher in sauropsidians than in mammals, particularly in primates.

ISSN:0092-7317    

DOI:10.1002/cne.901990306

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

年代:1981

数据来源: WILEY

摘要:

AbstractUsing the HRP retrograde transport technique in two different genera of owls (SpeotytoandTyto), we have studied the distribution of neurons projecting to the optic tectum and the visual thalamus. Small injections of HRP were made into these structures from the pial surface after they had been visualized directly by dissection of the overlying bone.In contrast to the findings in mammals, retinal ganglion cells were labeled only in the eye contralateral to the injection site, whether this was in the thalamus or tectum, and the labeled ganglion cells were found on both nasal and temporal sides of the vertical retinal meridian through the fovea. After thalamic injection, labeling was prominent in temporal retina representing the binocular field, temporal to the optic nerve head. Retinothalamic ganglion cells formed roughly concentric lines of isodensity centered on the fovea (Speotyto) orarea centralis (Tyto); labeling form thalamic injections involved both large and medium‐sized neurons, but did not involve the smallest nor a conspicuous class of very large neurons. Tectal injections led to prominent labeling along the horizontal streak region, with horizontally elongated isodensity contours in bothTytoandSpeotyto; retinotectal ganglion cells were heterogeneous and included a group of very large neurons and another group of small neurons, neither of which was labeled from the thalamus.In the visual Wulst, labeled neurons were confined to the supragranular layers after both tectal and thalamic injections. Corticotectal neurons were found in both ipsilateral and contralateral visual Wulst. They were characterized by large cell bodies and prominent dendrites. Corticotectal neurons were distributed throughout the mediolateal extent of the ipsilateral Wulst and therefore involved both the monocular and binocular representations of the visual field. Corticothalamic neurons, found only in the ipsilateral Wulst, were characterized by smaller cell bodies and fine dendrites. They were confined to the monocular crescent on the extreme medial edge of the Wuls

ISSN:0092-7317    

DOI:10.1002/cne.901990307

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

年代:1981

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901990301

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

年代:1981

数据来源: WILEY