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Showing papers on "Orientation column published in 1993"


Journal ArticleDOI
25 Feb 1993-Nature
TL;DR: It is reported here that ganglion cells near the fovea were allocated 3.3 to 5.9 times more cortical tissue than more peripheral ones, and it is concluded that the cortical representation of the most central retina is much greater than expected from the density of its ganglions.
Abstract: The retinal fovea, which corresponds to the central degree or so of vision, is spatially over-represented in the visual cortex. It is about 0.01% of retina area, but at least 8% of the striate cortex. Does this simply reflect an equivalently uneven distribution of ganglion cells in the retina, or is the cortical representation of the fovea preferentially expanded? The answer hinges on the resolution of long-standing discrepancies between the retinal and cortical magnification factors. We approached the problem in a different way, using a retrograde transneuronal tracer from cortex to retina to relate directly the number of ganglion cells projecting to marked areas of striate cortex. We report here that ganglion cells near the fovea were allocated 3.3 to 5.9 times more cortical tissue than more peripheral ones, and conclude that the cortical representation of the most central retina is much greater than expected from the density of its ganglion cells.

181 citations


Journal ArticleDOI
TL;DR: Data obtained from experiments using a bipartite visual stimulus showed that bringing the stimulus into alignment resulted in a 24.28% increase in the surround antagonism of the centre response, which supports the view that an entire subset of cortical orientation columns generate the feedback influencing any given dLGN cell.
Abstract: In a previous study, we have shown that the corticofugal projection to the dLGN enhances inhibitory mechanisms underlying length tuning. This suggests that the inhibitory influences deriving from the corticofugal feedback should exhibit characteristics that reflect the response properties of orientation-tuned layer VI cells. Here we report data obtained from experiments using a bipartite visual stimulus, with an inner section over the dLGN cell receptive field centre and an outer section extending beyond it. For both X and Y cells there was a modulation of the strength of the surround antagonism of centre responses that was dependent on the orientation alignment of contours in the two components of the stimulus. Layer VI cells showed maximal responses when the two components were aligned to the same orientation; dLGN cells showed a minimal response. Varying the orientation alignment of the inner and outer components of the stimulus in a randomised, interleaved fashion showed that bringing the stimulus into alignment resulted in a 24.28% increase in the surround antagonism of the centre response. Blocking cortical activity showed this effect of alignment to be strongly dependent on corticofugal feedback. This effect of orientation alignment appears to apply for any absolute orientation of the alignment condition and supports the view that an entire subset of cortical orientation columns generate the feedback influencing any given dLGN cell. This mechanism makes dLGN cells sensitive to the orientation domain discontinuities in elongated contours moving across their receptive field.

147 citations


Journal ArticleDOI
TL;DR: The results reaffirm the existence of multiple extrastriate visual areas in the rat and provide a definition of the retinotopy of some areas that have not been completely mapped before.
Abstract: Previous studies have determined that the striate cortex of the rat is reciprocally connected with multiple extrastriate cortical areas that are retinotopically organized. The objective of this study was to investigate the retinotopy of the striate-extrastriate connections in the rat, by placing triple or double injections of fluorescent tracers (fluorogold, fast blue, rhodamine dextran, or rhodamine-labeled microspheres) in different regions of the striate cortex (Oc1) and mapping the distribution of cells and fibers labeled with the different tracers in the lateral (Oc2L) and medial (Oc2M) extrastriate cortex. The tracer injection sites were visualized in tangential sections of the flattened cortex and correlated with the myelin layout of the striate cortex and with an electrophysiological map from previous studies. The results showed retinotopically organized Oc1 connections with ten different extrastriate cortical areas. The location of these extrastriate areas and the retinotopy of their striate connections remained mostly invariant despite changes of the injection sites in Oc1. Thus, the quadrantic retinotopy was obtained for striate connections to areas posterior, posterolateral, lateromedial, laterointermediate, laterolateral, anterolateral and rostrolateral in Oc2L; and to areas posteromedial, anteromedial, and anterior in Oc2M. The present anatomical map correlates well with electrophysiological maps of the rat extrastriate cortex from previous studies. Furthermore, they provide a definition of the retinotopy of some areas that have not been completely mapped before. These results reaffirm the existence of multiple extrastriate visual areas in the rat.

110 citations


Journal ArticleDOI
TL;DR: Single neurons were recorded in the striate visual cortex of the old-world monkey Macacus nemestrinus, and the laminar specificity of the boutons was very much more precise in the monkey than in the cat.
Abstract: Single neurons were recorded in the striate visual cortex (area 17) of the old-world monkey Macacus nemestrinus. Eight pyramidal neurons, seven spiny stellate neurons, two basket cells, a clutch cell, and a chandelier cell were filled intracellularly with HRP. Their receptive fields were consistent with previous single-unit studies. Their axonal arbors were less elaborate than in equivalent neurons in the cat, but the laminar specificity of the boutons was very much more precise in the monkey than in the cat. Nevertheless, the basic cortical circuits in cat and monkey appear to be very similar.

60 citations


Journal ArticleDOI
TL;DR: A neural network model for explaining experimentally observed neuronal responses in cat primary visual cortex that satisfactorily account for experimental observations is proposed.
Abstract: A neural network model for explaining experimentally observed neuronal responses in cat primary visual cortex is proposed. In our model, the basic functional unit is an orientation column which is represented by a large homogeneous population of neurons modeled as integrate-and-fire type excitable elements. The orientation column exhibits spontaneous collective oscillations in activity in response to suitable visual stimuli. Such oscillations are caused by mutual synchronization among the neurons within the column. Numerical simulation for various stimulus patterns shows that as a result of activity correlations between different columns, the amplitude and the phase of the oscillation in each column depend strongly on the global feature of the stimulus pattern. These results satisfactorily account for experimental observations.

40 citations


Journal ArticleDOI
TL;DR: Ablation of visual cortical areas 17 and 18 in neonatal and young adult cats induces novel retinal projections to terminate bilaterally in the lateral posterior nucleus at a position ventromedial from the medial interlaminar nucleus.
Abstract: Ablation of visual cortical areas 17 and 18 in neonatal and young adult cats induces novel retinal projections to terminate bilaterally in the lateral posterior nucleus (LP) at a position ventromedial from the medial interlaminar nucleus. Comparison with the visual-field maps of LP indicate that the terminations are focussed on the representation of the visual-field center.

23 citations


Journal ArticleDOI
TL;DR: In the cat visual cortex, binocular convergence seems to occur so early in cortical processing that monocular stimulation with many orientations leads to a rather homogeneous activation of cortical tissue.
Abstract: Extending previous investigations of the topographic relationship between ocular dominance and orientation columns in the cat visual cortex the two systems were visualized with transneuronally transported [3H]proline and with activity-dependent uptake of [14C]2-deoxyglucose, respectively. In addition, we used the 2-deoxyglucose method for a functional assay of both columnar systems. To this end, cats were injected with [3H]proline in the right eye. Two weeks later, they were stimulated monocularly through this eye by presenting contours of only a single orientation in the left and contours of many different orientations in the right visual hemifield while 2-deoxyglucose was injected. The patterns of increased 2-deoxyglucose uptake and of terminal labelling were analysed in flat-mount sections of the visual cortices and in frontal sections of the lateral geniculate nuclei. In the lateral geniculate nucleus, regions of increased 2-deoxyglucose uptake are in register with the [3H]proline-labelled laminae of the open eye. In the visual cortex, the hemispheres stimulated with many different orientations showed a rather homogeneous accumulation of 2-deoxyglucose over the entire extent and throughout all layers of area 17. The hemispheres stimulated with a single orientation displayed columnar patterns of orientation domains essentially similar to those obtained with binocular presentation of a single orientation. In particular and despite monocular stimulation, regions of increased 2-deoxyglucose uptake were neither in register with the [3H]proline-labelled terminals of the increased 2-deoxyglucose uptake were neither in register with the [3H]proline-labelled terminals of the stimulated eye in layer IV nor confined to columns of neural tissue above and below these terminals. The maximal horizontal offset between the termination sites of thalamic afferents and activated orientation columns was in the order of 400 microns. These findings suggest several conclusions. (i) In the cat visual cortex, binocular convergence seems to occur so early in cortical processing that monocular stimulation with many orientations leads to a rather homogeneous activation of cortical tissue. (ii) From the termination zones of geniculate afferents activity is apparently distributed already within layer IV to the respective orientation columns. (iii) This horizontal spread of activity could be assured by target cells with radially extending dendrites and/or tangentially oriented fibres.

18 citations


01 Jan 1993
TL;DR: This work compute the functional inner products of a two dimensional input signal image with a set of two dimensional Gabor functions which have been shown to be receptive to the receptive elds of simple cells in the primary visual cortex of mammals.
Abstract: This work presents explorations in the microstructure of natural vision systems based on large scale computer simulations Similarly to previous work in this area we compute the functional inner products of a two dimensional input signal image with a set of two dimensional Gabor functions which have been shown to t the receptive elds of simple cells in the primary visual cortex of mammals These inner products are then considered as net inputs to the cortical cells and used to compute the cell activations as non linear functions A previously used model is extended with a pixel wise winner takes all competition between di erent Gabor lters which is introduced in order to model lateral inhibition between cortical cells The e ect of lateral inhibition is qualitatively estimated by visualization of computed cortical images and quantitatively evaluated by applying the model to a face recognition problem Recognition rate of was achieved on a database of face images of persons vs achieved with a previously used model

17 citations


Journal ArticleDOI
TL;DR: The approach shows that the complex appearance of cortical orientation columns has a rather simple description in the Fourier domain, and explains why singularities in the cortex do not have vorticities other than ±1/2.
Abstract: We demonstrate that the map of the preferred orientations and the corresponding map of the orientation tuning strengths as measured with optical imaging are not independent, but that band-pass filtering of the preferred orientation map at each location yields a good approximation of the orientation tuning strength. Band-pass filtering is performed by convolving the map of orientation preference with its own autocorrelation function. We suggest an interpretation of the autocorrelation function of the preferred orientations as synaptic coupling function, i.e., synaptic strength as a function of intracortical distance between cortical cells. In developmental models it has been shown previously that a "Mexican hat"-shaped synaptic coupling function (with a shape similar to that of the autocorrelation function) can produce a realistical-looking pattern of preferred orientations. Since optical imaging performs surface averaging, we discuss the possibility that the connection between the two maps is a measurement artifact of optical imaging. Whether this is the case can only be decided by combining electrode penetrations with optical imaging techniques for which we suggest experiments. We present a model for the generation of both maps from a single computational concept. The model is based on inverse Fourier transform of rather simple two-dimensional annulus-shaped spectra which will produce a column structure very similar to real data. Thus, our approach shows that the complex appearance of cortical orientation columns has a rather simple description in the Fourier domain. Our theoretical analysis explains why singularities in the cortex do not have vorticities other than ±1/2, a result which corresponds to recent experimental findings. This study combines the results from several modeling approaches with recently available optical imaging data to construct a model of both aspects (angle and strength) of the cortical orientation column system. This could alter ideas about cortical development if the link between the two maps can be established as a physiological result.

13 citations


Book ChapterDOI
01 Jan 1993
TL;DR: In this article, the authors show that the orientation column structures of the cat's preferred orientation can be mapped to a power spectrum which has a rather simple annulus-like structure.
Abstract: The input to primary visual cortex is embedded in a high dimensional feature space whose dimensions include position in visual space, preferred orientation, ocular dominance etc. Since all cells in a column with axis perpendicular to the cortical surface have approximately the same properties [4], this space is effectively mapped on a two-dimensional space, the cortical plane. This dimension reduction leads to complex maps which so far have evaded intuitive understanding. We show that their most salient features can be understood from a few basic design principles, in particular, local correlation, isotropy and homogeneity. These principles can be defined most easily in the Fourier domain where they correspond to a power spectrum which has a rather simple annulus-like structure. After inverse Fourier transformation, we obtain maps of orientation column structures which are very similar to the experimentally observed orientation column maps of the cat. We show this by comparison with maps which were obtained by optical imaging methods. We expect that many of the models which have been developed to explain the mapping of the preferred orientations (e.g., [5, 7, 6, 8, 10, 11, 13]) can be subsumed under our approach.

10 citations


Journal ArticleDOI
TL;DR: The axonal tracer HRP-WGA was used in conjunction with AChE histochemistry to demonstrate that a reciprocal pathway links area 21a with the LPl (striate recipient zone) in the lateral posterior-pulvinar complex.

Book ChapterDOI
01 Jan 1993
TL;DR: This chapter discusses experiments to understand how the corticogeniculate pathway is organized in relation to the parallel granular and supragranular ascending systems and suggests that neurons in layer VI of striate cortex are in a position to selectively influence the transmission of activity in these two pathways.
Abstract: Publisher Summary One of the major advances in the understanding of functional organization of the visual system has been the identification of parallel geniculocortical pathways that link different populations of retinal ganglion cells with different layers of the striate cortex. Despite variation across species in the features that distinguish these pathways, two general classes can be identified in all: those that terminate in the granular layer of striate cortex, layer IV; and those that terminate in the supragranular layers, layers I-III. It has also been found that the projections from the lateral geniculate nucleus (LGN) to the striate cortex, like all thalamocortical pathways, are reciprocated by a dense feedback projection that originates from neurons in cortical layer VI. This chapter also discusses experiments to understand how this descending pathway is organized in relation to the parallel granular and supragranular ascending systems. The results suggest that neurons in layer VI of striate cortex are in a position to selectively influence the transmission of activity in these two pathways by virtue of their descending projections to the LGN as well as their local axonal projections to the granular and supragranular layers of the striate cortex. To examine the organization of the corticogeniculate pathway, small extracellular injections of biocytin are made into layer VI of tree shrew striate cortex and then the pattern of labeled axons in the LGN are examined.


Journal ArticleDOI
TL;DR: There is a higher synaptic density in the region of the visual cortex receivinginput from a retinal area with a high ganglion cell concentration than the area of the cortex receiving input from the retina with a low concentration of such cells.
Abstract: In the adult pigmented rabbit, synaptic density in the lateral and medial part of the visual cortex was estimated along the projection area of the visual streak. A higher synaptic density distribution was observed in the lateral cortex (projection area of the nasal visual field) than in the medial cortex (projection area of the temporal visual field). This shows that there is a higher synaptic density in the region of the visual cortex receiving input from a retinal area with a high ganglion cell concentration than the area of the cortex receiving input from the retina with a low concentration of such cells. The regions of the visual cortex with higher and lower synaptic densities are the areas having a higher and lower magnification factor respectively.


Book ChapterDOI
01 Jan 1993
TL;DR: By using positron emission tomography with an experimental paradigm related to the detection of horizontal disparity in Julesz type stereograms, the areas in the human brain that are specifically engaged in binocular disparity detection mediated by the Detection of shape are discussed.
Abstract: Publisher Summary The neuronal mechanisms of binocular vision presuppose sophisticated anatomical connections stemming from the fact that binocular cells in the visual cortex receive information from the two eyes' corresponding receptive fields. This chapter discusses by using positron emission tomography (PET) with an experimental paradigm related to the detection of horizontal disparity in Julesz type stereograms, the areas in the human brain that are specifically engaged in binocular disparity detection mediated by the detection of shape. The data clearly indicates that the analysis and processing of stereoptic disparity information takes place in the polar striate cortex and the neighbouring peristriate cortices. To analyze the involvement of the striate cortex in stereovision, the location and size of the activated regions was determined in 1 cm thick mesial parasagittal brain slices left and right of the midline. The regions activated by disparity detection on the mesial surface of the striate well correspond to the topographic representation of the centre of the visual field up to 5°.

Proceedings ArticleDOI
25 Oct 1993
TL;DR: The HRP technique is used to identify the cortico-cortical neurons which project to the facial or trunk-hindlimb regions of SV and found a new and complete somatosensory representation of the body surface.
Abstract: It is known that there are at least four separate somatosensory cortical representations in the cat's cortex. These areas had many cortico-cortical connections in the cerebral cortex. Furthermore, Mori et al. found a new and complete somatosensory representation of the body surface located rostro-caudally along the medial bank of the anterior suprasylvian sulcus (ASSS-m), the fifth somatosensory cortex (SV). These neurons had large receptive fields (RFs). In the present study, we used the HRP technique to identify the cortico-cortical neurons which project to the facial or trunk-hindlimb regions of SV.

01 Jan 1993
TL;DR: Optical recordings of neural activity in the primary visual cortex have shown that although there are regions of the cortex where a smooth gra- dation of preferred orientation appears, there are also discontinuities and distortions in the mapping, where modules having markedly different preferences are oc- casionally neighbours.
Abstract: In now classical experiments, David Hubel and Torsten Wiesel recorded action potentials from neurons in the monkey primary visual cortex while presenting bars of light or edges of various orientations in front of the eyes [l]. Advancing their electrode through the corti- cal tissue in directions tangential to the cortical surface, they observed many neiglhbouring cells with similar speci- ficity for the orientation of bars, and saw ordered changes in this preferred orientation as the penetration extended over greater distances. Penetrations perpendicular to the cortical surface revealed cells with very similar orientation preference throughout the depth of the cortical mantle, and together these features suggested that the stimulus dimension of orientation was mapped in an orderly fash- ion across the cortical surface, in a system of ‘ columns’ or ‘ modules’ of like-mind.ed cells. These findings, and the additional one that the c:ells’ preferences for the eye of stimulation (ocular dominance) are similarly mapped in an orderly fashion, have been summarized in the ‘ ice- cube’ model of the organization of visual cortex, famil- iar from every physiology textbook, in which orientation and ocular dominance are mapped orthogonally in regular ‘ hypercolumns’ that contain every combination of these two dimensions. It is now thought that that the mapping between these stimulus dimensions and their representation in the cor- tex is not quite so simpl!e. Optical recordings of neural activity in the primary visual cortex ([2], and see [3] for a recent review) have shown that although there are, indeed, regions of the cortex where a smooth gra- dation of preferred orientation appears, there are also discontinuities and distortions in the mapping, where modules having markedly different preferences are oc- casionally neighbours. An attractive means of account- ing for this organization is that it represents a mapping from a ‘ stimulus space’ , which has many dimensions, to the two dimensions of the cortex [4]. In the case of a stimulus space consisting of an orientation dimension, an ocular dominance dimens#ion and two dimensions of reti- nal position, for example, neighbourhood relations in the stimulus space can be largely preserved in mapping to the two-dimensional cortex only by allowing occasional discontinuities and distorllons. It is not too diEcult to imagine that this type of mapping might go a long way towards accounting for the relations between various stimulus spaces and their corresponding cortical maps in the many other visual cortical areas that extend across most of the back of the cerebrum. Most areas are populated by cells that show selectivity for sim- ilarly simple stimulus dimensions, whether it be direction

Proceedings ArticleDOI
08 Sep 1993
TL;DR: It is suggested that the initial phase of neural response encodes the location of the visual stimulus, whereas the later phase encodes its orientation, and the model of neural network system for image processing based on the iso-orientation domain model and the above idea is proposed.
Abstract: The objectives of the research were: (1) to investigate the dynamics of neuron responses and orientation selectivity in the primary visual cortex; (2) to find a possible source of bifurcation of visual information into `what' and `where' processing pathways; (3) to apply the obtained results for visual image processing. To achieve the objectives, a model of the iso-orientation domain (orientation column) of the visual cortex has been developed. The model is based on neurophysiological data and on the idea that orientation selectivity results from a spatial anisotropy of reciprocal lateral inhibition in the domain. Temporal dynamics of neural responses to oriented stimuli were studied with the model. It was shown that the later phase of neuron response had a much sharper orientation tuning than the initial one. The results of modeling were confirmed by neurophysiological experiments on the visual cortex. The findings allow us to suggest that the initial phase of neural response encodes the location of the visual stimulus, whereas the later phase encodes its orientation. Temporal dividing of information about object features and their locations at the neuronal level of the primary visual cortex may be considered to be a source for bifurcation of the visual processing into `what' and `where' pathways and may be used for parallel-sequential attentional image processing. The model of neural network system for image processing based on the iso-orientation domain model and the above idea is proposed. An example of test image processing is presented.

01 Jan 1993
TL;DR: A functional model called ED-chan is suggested to explore the meaning or usefulness of orientation specificity, and the results show that intermediate features such as ends, corners and crosses are being abstracted through self-organization.
Abstract: We propose an €&-chart, lmergent Local Indicator Mechanism, to model the representation and selforganization of intermediate features in the visual pathway. This model is motivated by the orientation specificity in the primary visual cortex. Our simulations of €@-chan demonstrate that local indicators of the locations of intermediate features emerge, and they become the seeds for unsupervised learning and pattern recognition; €0-chan predicts those portions of the input imagery where intermediate features potentially exist. Hence, E&-chun can be used to define a set of intermediate features for adaptation, and the onwards processing in a hierarchical pattern recognition system. Visual pathway processes information hierarchically, so that the external world is perceived via a series of feature abstractions. At the primary level, simple cells and complex cells in the primary visual cortex exhibit orientation specificity; the visual world is being dissected into line segments of various orientations. Furthermore, neurons with the same orientation specificity are grouped together into orientation columns, and these columns are regularly arranged in a stepwise or quasi-continuous fashion from Oo to 360°, to cater for all possible orientations in a given area of the visual field [l]. Why is the primary visual cortex (area 17) organized according to orientation specificity? While it is apparent that the decomposition of the visual world into line segments of various orientations is necessary for the discrimination of form and movement in the early vision, its significance for the representation of features at the intermediate level (area 18) is not well understood. In this paper, we suggest a functional model called ED-chan to explore the meaning or usefulness of orientation specificity. We have simulated lfi-chan on personal computer, and the results show that intermediate features such as ends, corners and crosses are being abstracted through self-organization. With €0-chan, we can construct a hierarchical neural net to self-learn and recognize objects in the visual world.

Proceedings ArticleDOI
25 Oct 1993
TL;DR: A new model of information processing in the visual cortex is proposed that uses lateral inhibition and temporally segregated activations between cortical neurons, resulting in predictive coding, based on the segregation of the times of arrival in theVisual cortex of signals originating from the retina and relayed in the lateral geniculate nucleus.
Abstract: We propose a new model of information processing in the visual cortex for the analysis of motionless images. It uses lateral inhibition and temporally segregated activations between cortical neurons, resulting in predictive coding. It is in agreement with some characteristics of the architecture of the visual cortex of the monkey. The model is based on the segregation of the times of arrival in the visual cortex of signals originating from the retina and relayed in the lateral geniculate nucleus. This distribution of delays depends both on the type of ganglion cell, of its position on the retina, and of its modulation by the cortical network. Indeed the parallel channels into which the retinal image is decomposed are represented as delay lines; and the resulting spatially uniform and discrete distribution of delays is modulated by spatial factors determined by the geometry of the retina.