Cytoarchitectural differences are a key determinant of laminar projection origins in the visual cortex (original) (raw)
Related papers
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2000
The directionality of corticocortical projections is classified as feedforward (going from a lower to higher hierarchical levels), feedback (interconnecting descending levels), and lateral (interconnecting equivalent levels). Directionality is determined by the combined criteria of the laminar patterns of the axon terminals as well as the cells of origins and has been used to construct models of the visual system, which reveals a strict hierarchical organization (Felleman and Van Essen, 1991; Hilgetag et al., 1996a). However, these models are indeterminate partly because we have no indication of the distance separating adjacent levels. Here we have attempted to determine a graded parameter describing the anatomical relationship of interconnected areas. We have investigated whether the precise percentage of labeled supragranular layer neurons (SLN%) in each afferent area after injection in either visual areas V1 or V4 determines its hierarchical position in the model. This shows that...
Projections from Areas 18 and 19 to Cat Striate Cortex: Divergence and Laminar Specificity
European Journal of Neuroscience, 1991
The results of electrical stimulation experiments [Bullier et a/., (1988) Exp. Brain Res., 70, 90-981 demonstrated that afferents from areas 18 and 19 contact different functional types of neurons in area 17. We were therefore interested in examining whether these results could be explained by differences in the morphology of the terminals of these two groups of afferent connections to area 17. We also wanted to confirm, by a direct method, our earlier results [Salin et a/. (1989) J. Comp. Neurol., 283, 486-5121 that cortical afferents to area 17 in the cat present extensive divergences. We therefore placed small injections of anterograde tracers in areas 18 and 19 and examined the laminar distributions of terminals thus revealed and the extent of the surface of area 17 contacted by these terminals. Three tracers were used: wheat germ agglutininhorseradish peroxidase (WGA -HRP), Phaseolus vulgaris leucoagglutinin (Pha-L) and biocytin.
A predictive model of the cat cortical connectome based on cytoarchitecture and distance
Brain Structure and Function, 2014
Information processing in the brain is strongly constrained by anatomical connectivity. However, the principles governing the organization of corticocortical connections remain elusive. Here, we tested three models of relationships between the organization of cortical structure and features of connections linking 49 areas of the cat cerebral cortex. Factors taken into account were relative cytoarchitectonic differentiation ('structural model'), relative spatial position ('distance model'), or relative hierarchical position ('hierarchical model') of the areas. Cytoarchitectonic differentiation and spatial distance (themselves uncorrelated) correlated strongly with the existence of inter-areal connections, whereas no correlation was found with relative hierarchical position. Moreover, a strong correlation was observed between patterns of laminar projection origin or termination and cytoarchitectonic differentiation. Additionally, cytoarchitectonic differentiation correlated with the absolute number of corticocortical connections formed by areas, and varied characteristically between different cortical subnetworks, including a 'rich-club' module of hub areas. Thus, connections between areas of the cat cerebral cortex can, to a large part, be explained by the two independent factors of relative cytoarchitectonic differentiation and spatial distance of brain regions. As both the structural and distance model were originally formulated in the macaque monkey, their applicability in another mammalian species suggests a general principle of global cortical organization.
European Journal of Neuroscience, 2005
Current hierarchical models of the cerebral cortex are mainly based on qualitative connection studies. From wheatgerm-agglutininhorseradish peroxidase injections, we examined the laminar patterns of projections to and between the three major subdivisions of the motion-processing lateral suprasylvian (LS) complex [areas posteromedial lateral suprasylvian area (PMLS), anteromedial lateral suprasylvian (AMLS), posterolateral lateral suprasylvian area (PLLS)] of cat extrastriate cortex and of an adjoining form-processing area, 21a. We counted 145,000 labelled projection cells in 20 cortical areas in 11 cats, and applied various analyses to the data, expressed as the percent supragranular layer (%SG) origin of each connection. We report two main results. (i) A wide range of %SG values was obtained, both from each individual cat and across the 163 projections examined. Nonetheless, both hierarchical and non-parametric cluster analyses of the pooled connection origins suggested the presence of three distinct laminar projection classes, constrained by graded %SG values of 0-33%, 39-69% and 76-97%. These conformed, respectively, to feedback, lateral and feedforward laminar patterns seen qualitatively in our material. (ii) Hierarchical connectivity analyses suggested that PMLS, AMLS and PLLS are ordered in a hierarchical sequence. Macaque motion areas V5 ⁄ MT, MST and FST are arranged in a similar sequence, and areas at equivalent levels of the two motion hierarchies have some analogous functional specializations. Our findings provide the first objective support for the three laminar projection classes that underpin existing theoretical models of hierarchical cortical organization, and they suggest that the implementation of higher-order motion processing evolved along similar lines in the cat and monkey visual cortex.
Morphological types of projection neurons in layer 5 of cat visual cortex
Journal of Comparative Neurology, 1990
Pyramidal cells in layer 5 of the visual cortex have multiple cortical and subcortical projection sites. Previous studies found that many cells possess bifurcating axons and innervate more than one cortical or subcortical target, but cells projecting to both cortical and subcortical targets were not observed. The present study examines the morphology of cells in cat visual cortex projecting to the superior colliculus, the main subcortical target of layer 5 , and cells in layer 5 projecting to cortical areas 18 and 19. The neurons that give rise to these different projections were retrogradely labelled and intracellularly stained in living brain slices. Our results show that cells within each projection group have several morphological features in common. All corticotectal cells have a long apical dendrite forming a large terminal tuft in layer 1. Their cell bodies are medium sized to large, and their basal dendrites form a dense and symmetrical dendritic field. Corticocortical cells in layer 5 have a very different morphology: their apical dendrites are short and they never reach higher than layers 213. Their cells bodies are small to medium sized and they have fewer basal dendrites than corticotectal cells. Thus there are two morphologically distinct projection systems in layer 5 , one projecting to cortical and the other one to subcortical targets, suggesting that these two systems transmit different information from the visual cortex. Among the corticotectal cells with the largest cell bodies we found some cells whose basal and apical dendrites were almost devoid of spines. Spiny and spinefree corticotectal cells also have different intrinsic axon collaterals and therefore play different roles in the cortical circuitry. While many spiny corticotectal cells have axon collaterals that project to layer 6, spinefree corticotectal cells have fewer axon collaterals and these do not arborize in layer 6. We suggest that the two morphological types of corticotectal cells might be related to functional differences known to exist among these cells. We discuss how the presence or absence of spines affects the integration of the synaptic input and how this might be related to the cells' functional properties. Key w o r h cortical circuitry, dendritic spines, Meynert cell, brain slices, intracellular labelling Single cell recording in the visual cortex revealed many different types of neurons with specialized functional properties designed to process particular features of objects, such as form, motion, position in depth, or color. Since it is known from anatomical studies that cortical cells occur in a large variety of morphological forms, one might expect to find a correspondence between some functional aspects of a cell and its structure. A direct way to examine structurefunction relationships is to record intracellularly from a cell, determine its receptive field properties, and then inject the same cell with a dye (Kelly and Van Essen, '74; Gilbert and Wiesel, '79; Lin et al., '79; Parnavelas et al., '83; Martin and Whitteridge, '84a). This approach allows one to visualize the dendritic and axonal branching patterns of functionally identified cells and provides important insights into the cortical circuitry. However, it turned out that it is rather difficult to find a direct correspondence between structural features of cortical cells and certain receptive field properties. For example, the data of an early study (Kelly and Van Essen, '74) seem to suggest that there is a relationship between simple and complex receptive fields with stellate and pyramidal cell morphology, but subsequent studies (Gilbert and Wiesel, '79; Martin and Whitteridge, '84a) found no such correlation. Gilbert and Wiesel('79) reported that cells with larger dendritic arbors tend to have larger receptive fields, while Martin and Whitteridge ('84b) could
Brain Research, 1985
Key words: cortical visual area --interhemispheric connection --cat --fluorescent retrograde tracer lntra-and interhemispheric connections between the anterior ectosylvian visual area (AEV) and other visual cortical areas including the lateral suprasylvian (LSS) were examined in the cat using the retrograde double-label fluorescence technique. The areal and laminar distributions of labeled neurons were mapped following injections of different tracers: Evans Blue (EB), Fast Blue (FB) and Nuclear Yellow (NY) made separately into AEV and LSS of the same or opposite hemispheres. The results indicated: (1) reciprocal and bilateral AEV-LSS connections stemming from layers V and VI in addition to a predominant efferent LSS projection upon AEV from both layer III and the posterior lateral (PLLS) subdivision of LSS; (2) homotopic interhemispheric connections to AEV arising from layers III, V and VI and from layers III and V of ipsilateral areas 20 and 21a; (3) differential laminar distributions of the cell populations projecting to the two cortical sites injected including neurons in layer III of LSS which project to contralateral LSS and AEV of either hemisphere via collateral axon branching (double-labeled). The anatomical findings support the functional similarities between AEV and LSS and the possible role of AEV in interhemispheric transfer of visual information is discussed.
Laminar origins of visual corticocortical connections in the cat
The Journal of Comparative Neurology, 1984
The interconnections among visual areas in cat cortex were studied with respect to the specific laminae in which the cortically projecting neurons are located. Single injections of HRP were made through recording micropipettes into nine different visual areas. In 15 cortical areas the laminar distribution of neurons which were retrogradely filled with HRP was plotted. In this way we determined the laminar origins of the cortical projections to the nine separate cortical visual areas which were injected. There are three major observations. First, areas 17 and 18 are the only two visual areas in which layers I1 and I11 are the primary site of cortically projecting cells; in the other 13 areas the deeper layers of cortex provide a large percentage of such neurons. Second, within any one cortical area, cortically projecting neurons may be distributed among different layers; the specific layer depends upon the cortical target of those neurons. Third, any one cortical area receives projections from several different cortical layers, the specific layers being dependent upon the area from which the projection originates. An individual cortical area, therefore, contributes to several different cortical visual circuits, with each of these circuits defined by the laminar connections of its neurons.
Visuotopic organization of corticocortical connections in the visual system of the cat
The Journal of Comparative Neurology, 1992
It has recently been demonstrated that, in contrast with the retinogeniculocortical projection, the corticocortical connections in the cat present a high degree of convergence and divergence. This suggests that some corticocortical connections link nonvisuotopically corresponding regions. Using fine-grain electrophysiological mapping and anatomical tracing, we have set out to test this possibility by placing a small injection of retrograde tracer in area 17 and by comparing the extent of visual field encoded in the region of area 18 containing labeled cells and that represented in the uptake zone. The results demonstrate that the size of the labeled region on the surface of area 18 is independent of eccentricity and that, despite its anisotrophy, this region of labeling encodes a broadly circular region of visual field that is larger than that encoded in the uptake zone of the tracer in area 17. For example, in the representation of lower visual field, a virtual point in area 17 that encodes a visual field region 4" in diameter receives afferents from a region of area 18 encoding a region 11" wide. Examination of the density of labeled cells in the labeled zone in area 18 reveals that the highest density is observed in a region in visuotopic correspondence with the injection site. However, high labeling density is also occasionally found in patches that do not represent the same visual field region as the injection site. Many receptive fields of neurons recorded in the labeled zone in area 18 only partially overlap or fail to overlap the visual field region encoded by the injection site. The results also demonstrate that the extent of visual field encoded in the labeled zone in area 18 is the same as that represented in the region of intrinsic labeling in area 17. It is suggested that cortical afferents coming from several cortical areas and converging on a column of cells in area 17 cover the same extent of visual field and that this cortical network constitutes the structural basis for the modulatory regions of the receptive field as well as the synchronization of neurons in different cortical areas.