Showing papers on "Orientation column published in 2001"
TL;DR: The connections along the retinogeniculocortical pathway show a precision that goes beyond simple retinotopy to include many other response properties, such as receptive-field sign, timing, subregion strength, and size.
Abstract: Hundreds of thalamic axons ramify within a column of cat visual cortex; yet each layer 4 neuron receives input from only a fraction of them. We have examined the specificity of these connections by recording simultaneously from layer 4 simple cells and cells in the lateral geniculate nucleus with spatially overlapping receptive fields (n = 221 cell pairs). Because of the precise retinotopic organization of visual cortex, the geniculate axons and simple-cell dendrites of these cell pairs should have overlapped within layer 4. Nevertheless, monosynaptic connections were identified in only 33% of all cases, as estimated by cross-correlation analysis. The visual responses of monosynaptically connected geniculate cells and simple cells were closely related. The probability of connection was greatest when a geniculate center overlapped a strong simple-cell subregion of the same sign (ON or OFF) near the center of the subregion. This probability was further increased when the time courses of the visual responses were similar. In addition, the connections were strongest when the simple-cell subregion and the geniculate center were matched in position, sign, and size. The rules of connectivity between geniculate afferents and simple cells resemble those found for retinal afferents to geniculate cells. The connections along the retinogeniculocortical pathway, therefore, show a precision that goes beyond simple retinotopy to include many other response properties, such as receptive-field sign, timing, subregion strength, and size. This specificity in wiring emphasizes the need for developmental mechanisms (presumably correlation-based) that can select among afferents that differ only slightly in their response properties.
350 citations
TL;DR: FMRI was used to estimate the average receptive field sizes of neurons in each of several striate and extrastriate visual areas of the human cerebral cortex, and results are qualitatively in line with those obtained by others in macaque monkeys using neurophysiological methods.
Abstract: Functional magnetic resonance imaging (fMRI) was used to estimate the average receptive field sizes of neurons in each of several striate and extrastriate visual areas of the human cerebral cortex. The boundaries of the visual areas were determined by retinotopic mapping procedures and were visualized on flattened representations of the occipital cortex. Estimates of receptive field size were derived from the temporal duration of the functional activation at each cortical location as a visual stimulus passed through the receptive fields represented at that location. Receptive fields are smallest in the primary visual cortex (V1). They are larger in V2, larger again in V3/VP and largest of all in areas V3A and V4. In all these areas, receptive fields increase in size with increasing stimulus eccentricity. The results are qualitatively in line with those obtained by others in macaque monkeys using neurophysiological methods.
344 citations
TL;DR: Recent experimental and theoretical results in cat primary visual cortex and in the whisker-barrel fields of rodent primary somatosensory cortex suggest common organizing principles for layer 4, the primary recipient of sensory input from the thalamus.
172 citations
TL;DR: It is found that axons in layer 3 spread out from the site of a tracer injection in an anisotropic manner and that this elongated distribution is aligned with the preferred orientation recorded at each site.
Abstract: One important aspect of the functional architecture of primary visual cortex is the circuitry that accounts for the receptive field properties of neurons. The anatomy that underlies retinotopy and ocular dominance is well known, but no anatomical structure related to orientation selectivity has been found in primates. We examined whether the arrangement of local axon systems projecting within the cortical layers might be correlated with orientation preference in New World monkeys. We found that axons in layer 3 spread out from the site of a tracer injection in an anisotropic manner and that this elongated distribution is aligned with the preferred orientation recorded at each site. Moreover, within a few degrees of the foveal representation, the majority of the axon terminals fall within or just outside of the limits of the cortical mapping of the classical receptive field. Thus local axons produce a field of monosynaptic excitation that aligns with orientation axes and reaches neurons that have receptive fields which are adjacent in visual space.
161 citations
TL;DR: Plasticity is not uniformly distributed across the cortex, and the same spike time-dependent learning rules that have been found in single-cell in vitro studies are also valid on the level of cortical maps.
160 citations
TL;DR: Recent studies of primary visual cortex (V1) redefine layers 3 and 4 of V1 in monkeys and show that monkeys, apes and humans have different laminar specializations.
100 citations
TL;DR: The high-resolution visuotopic organization of cat primary visual cortex, and the encoding of simple visual stimuli by ensembles of ganglion cells in the isolated turtle retina are studied.
100 citations
TL;DR: It is proposed that V3 contributes to the processing of stereoscopic depth information and that the parietal areas to which it projects use this information for the analysis of object depth and three-dimensional form.
Abstract: Recordings were made from single and small groups of cells in prestriate area V3 of the visual cortex of the Cynomolgus macaque (Macaca fascicularis). The majority of cells in V3 were selective for orientation and stereoscopic depth, these cells being segregated into two sets of functionally distinct columns. Orientation columns in V3 have been previously demonstrated; here we show that V3 also contains columns of segregated disparity-selective cells. On the basis of its cellular properties, functional organization, and intra-cortical connections, we propose that V3 contributes to the processing of stereoscopic depth information and that the parietal areas to which it projects use this information for the analysis of object depth and three-dimensional form.
95 citations
TL;DR: It is shown that, as early as 2 wk before eye-opening, visual stimuli presented through the closed eyelids can drive neuronal activity in LGN and striate cortex of the ferret, which could have important implications for the self-organization of visual cortex.
Abstract: In studies of the developing mammalian visual system, it has been axiomatic that visual experience begins with eye-opening. Any role for neuronal activity earlier in development has been attributed to the patterned spontaneous activity found in retina and lateral geniculate nucleus (LGN). Here we show that, as early as 2 wk before eye-opening, visual stimuli presented through the closed eyelids can drive neuronal activity in LGN and striate cortex of the ferret. At this age, spontaneous activity in cortex is much lower than in LGN, and the visual responses of many cortical, but not geniculate, neurons depend on the orientation of a moving grating. Furthermore the selectivity of cortical neurons to the orientation of gratings presented through the closed eyelids improves with age. Thus neuronal activity patterned by visual experience, rather than by spontaneous retinal activity, is present in visual cortex much earlier than previously thought. This could have important implications for the self-organization of visual cortex.
88 citations
TL;DR: It is shown that prospective visual cortical areas and corresponding thalamic nuclei in the embryonic rhesus monkey (Macaca mulatta) can be defined by combinatorial expression of genes encoding Eph receptor tyrosine kinases and their ligands, the ephrins, prior to obvious cytoarchitectonic differentiation within the cortical plate and before the establishment of reciprocal connections between the cortex plate and thalamus.
84 citations
TL;DR: Three case studies in which patients with visual disorders are investigated are presented and the experiments are able to show how the cortex is capable of modifying the visual field representation in response to abnormal input.
TL;DR: The visually responsive neurons in A1 probably account for the capacity of the auditory cortex to mediate visual behavior in ‘rewired hamsters’.
Abstract: We studied visually guided behavior and the visual response properties of single auditory cortex (A1) neurons in neonatally operated hamsters with surgically induced, permanent, ectopic retinal projections to auditory thalamic nuclei and to visual thalamic nuclei which normally receive little direct retinal input. The surgically induced retino-thalamo-cortical pathways can mediate visual guided behaviors whose normal substrate, the pathway from the retina to the primary visual cortex via the primary thalamic visual nucleus, is missing. The visually evoked response properties of A1 neurons resemble in many respects those of neurons in V1 of normal hamsters: many A1 neurons have well-defined visual receptive fields and preferences for orientation or direction of movement. In addition, some visually responsive cells in A1 are bimodal--they also respond to auditory stimuli. The visually responsive neurons in A1 probably account for the capacity of the auditory cortex to mediate visual behavior in 'rewired hamsters'.
TL;DR: It is concluded that, once stimulation parameters are adjusted for the small volume of the rat brain, the use of antidromic techniques may be an effective strategy to differentiate among projection neurons comprising different local circuits in supra- and infragranular circuits.
Abstract: Physiological studies of the rodent somatosensory cortex have consistently described considerable heterogeneity in receptive field properties of neurons outside of layer IV, particularly those in layers V and VI. One such approach for distinguishing among different local circuits in these layers may be to identify the projection target of neurons whose axon collaterals contribute to the local network. In vivo, this can be accomplished using antidromic stimulation methods. Using this approach, the axonal conduction properties of cortical efferent neurons are described. Four projection sites were activated using electrical stimulation: (1) vibrissal motor cortex, (2) ventrobasal thalamus (VB), (3) posteromedial thalamic nucleus (POm), and (4) cerebral peduncle. Extracellular recordings were obtained from a total of 169 units in 21 animals. Results demonstrate a close correspondence between the laminar location of the antidromically identified neurons and their anatomically known layer of origin. Axonal properties were most distinct for corticofugal axons projecting through the crus cerebri. Corticothalamic axons projecting to either VB or POm were more similar to each other in terms of laminar location and conduction properties, but could be distinguished using focal electrical stimulation. It is concluded that, once stimulation parameters are adjusted for the small volume of the rat brain, the use of antidromic techniques may be an effective strategy to differentiate among projection neurons comprising different local circuits in supra- and infragranular circuits.
TL;DR: The distributions of several anatomical markers in V1 of two experimentally strabismic Macaca nemestrina monkeys were examined, finding changes appear to be related to the loss of binocularity in cortical neurons, which has its most profound effects near OD column borders.
Abstract: Strabismus, a misalignment of the eyes, results in a loss of binocular visual function in humans. The effects are similar in monkeys, where a loss of binocular convergence onto single cortical neurons is always found. Changes in the anatomical organization of primary visual cortex (V1) may be associated with these physiological deficits, yet few have been reported. We examined the distributions of several anatomical markers in V1 of two experimentally strabismic Macaca nemestrina monkeys. Staining patterns in tangential sections were related to the ocular dominance (OD) column structure as deduced from cytochrome oxidase (CO) staining. CO staining appears roughly normal in the superficial layers, but in layer 4C, one eye's columns were pale. Thin, dark stripes falling near OD column borders are evident in Nissl-stained sections in all layers and in immunoreactivity for calbindin, especially in layers 3 and 4B. The monoclonal antibody SMI32, which labels a neurofilament protein found in pyramidal cells, is reduced in one eye's columns and absent at OD column borders. The pale SMI32 columns are those that are dark with CO in layer 4. Gallyas staining for myelin reveals thin stripes through layers 2–5; the dark stripes fall at OD column centers. All these changes appear to be related to the loss of binocularity in cortical neurons, which has its most profound effects near OD column borders. J. Comp. Neurol. 438:300–317, 2001. © 2001 Wiley-Liss, Inc.
TL;DR: Speed preferences in MT neurons are found to be unaffected by changes in stimulus pattern, supporting the hypothesis that these neurons represent retinal image velocities.
Abstract: Speed preferences in MT neurons are found to be unaffected by changes in stimulus pattern, supporting the hypothesis that these neurons represent retinal image velocities.
TL;DR: The model puts constraints on the feedback synaptic footprint and shows that its elongated shape does not play a crucial role in sensitivity to orientation discontinuity, but the inhibitory component of feedback must predominate overall.
Abstract: We model feedback from primary visual cortex to the dorsal lateral geniculate nucleus (dLGN). This feedback makes dLGN neurons sensitive to orientation discontinuity (Sillito et al., 1993; Cudeiro & Sillito, 1996). In the model, each dLGN neuron receives retinotopic input driven by layer 6 cortical neurons in a full set of orientation columns. Excitation is monosynaptic, while inhibition is through perigeniculate neurons and dLGN interneurons. The stimulus consists of drifting gratings, one within and the other outside a circular region centered over the receptive field of the model dLGN relay neuron we study. They appear as a single grating when they are aligned with equal contrast. The model reproduces experimental results showing an increasing inhibitory effect of feedback on the firing rate of dLGN neurons as the two gratings move towards the aligned position. Moreover, enhancement of dLGN cell center-surround antagonism by feedback is revealed by measuring the responses to drifting gratings inside a circular window, as a function of window radius. This effect is related to the observed length tuning of dLGN cells. Sensitivity to orientation discontinuity could be mediated in the model by feedback from either simple or complex cells. The model puts constraints on the feedback synaptic footprint and shows that its elongated shape does not play a crucial role in sensitivity to orientation discontinuity. The inhibitory component of feedback must predominate overall, but the feedback signal from a cortical neuron to a dLGN neuron with the same or nearby receptive-field center can be dominated by excitation. Predictions of the model include (1) robust stimuli for layer 6 cortical neurons give pronounced nonlinearities in the responses of dLGN neurons; (2) the sensitivity to orientation discontinuity at low contrast is twice that at high contrast.
Book•
01 Jan 2001
TL;DR: Glutamate-mediated responses in developing retinal ganglion cells, L.C. Chalupa the dynamics of primate retinal group cells, E.M. Kaplan the role of feedback connections in shaping the responses of visual cortical neurons, J.J. Walsh the metamodal organization of the brain.
Abstract: Glutamate-mediated responses in developing retinal ganglion cells, L.C. Liets, L.M. Chalupa the dynamics of primate retinal ganglion cells, E. Kaplan, E. Benardete BDNF/TRKB signaling in the developmental sculpting of visual connections, D.O. Frost thalamic relay functions, S.M. Sherman higher-order motion processing in the pulvinar, C. Casanova, L. Merabet, A. Desautels, K. Minville response properties in the pulvinar complex after neonatal ablation of the primary visual cortex, A. Desautels, C. Casanova the superior colliculus and its control of fixation behaviour via projections to brainstem omnipause neurons, A. Bergeron, D. Guitton a possible role of the superior colliculus in eye-hand coordination, L.L Nenburger, R. Kleiser, V. Stuphorn, L.E. Miller, K.-P. Hoffmann look and see - how the brain moves your eyes about, P.H. Schiller, E.J. Tehovnik nonvisual influences on visual-information processing in the superior colliculus, B.E. Stein, W. Jiang, M. Wallace, T. Stanford beyond the classical receptive field in the visual cortex, R. Freeman processing of second-order stimuli in the visual cortex, C.L. Baker, Jr., I. Mareschal the role of feedback connections in shaping the responses of visual cortical neurons, J. Bullier, J.-M. Hup , A.C. James, P. Girard cortical mechanisms of binocular stereoscopic vision, A.J. Parker, B.G. Cumming cortical plasticity revealed by circumscribed retinal lesions or artificial scotomas, B. Dreher, W. Burke, M.B. Calford neural analysis of visual information during locomotion, H. Sherk, G.A. Fowler behavioural cartography of visual functions in cat parietal cortex: areal and laminar dissociations, S.G. Lomber visual cortex organization in primates: theories of V3 and adjoining visual areas, J.H. Kaas, D.C. Lyon from attentional gating in macaque primary visual cortex to dyslexia in humans, T.R. Vidyasagar different spaces and different times for perception and action, M.A. Goodale asymmetrical masking between radial and parallel motion flow in transparent displays, M. Iordanova, M. W. von Grunau speculations on the neural basis of islands of blindsight, R. Fendrich, C. M. Wessinger, M.S. Gazzaniga "seeing" in the blind hemifield following hemispherectomy, A. Ptito, A. Fortin, M. Ptito visual pathways following cerebral hemispherectomy, D. Boire, H. Theoret, M. Ptito from visual consciousness to spectral absorption in the human retina, J. Faubert, V. Diaconu tickling the brain - studying visual sensation, perception and cognition by transcranial magnetic stimulation, A. Cowey, V. Walsh the metamodal organization of the brain, A. Pascual-Leone, R. Hamilton when the auditory cortex turns visual, M. Ptito, J.-F. Giguere, D. Boi. (Part contents).
TL;DR: It is demonstrated that manipulation of binocular vision in the adult modifies neither the location of the primary callosal cortical map nor its retinotopy, and it induces functional plastic changes in this map which lead to a significant widening of the area of visual space signalled through the corpus callosum.
Abstract: In the primary visual cortex of normally reared adult cat, neurons activated through the corpus callosum are almost entirely located at the 17/18 border. They display small receptive fields distributed along the central vertical meridian of the visual field and are orientation selective. Here we demonstrate that a few weeks of monocular deprivation or unilateral convergent strabismus produced in adulthood does not modify the cortical distribution of these neurons, but leads to an increase of their receptive field size mainly toward the ipsilateral hemifield and to a loss of their orientation selectivity. We conclude that manipulation of binocular vision in the adult modifies neither the location of the primary callosal cortical map nor its retinotopy. In contrast, it induces functional plastic changes in this map which lead to a significant widening of the area of visual space signalled through the corpus callosum. These plastic changes are interpreted as the result of the strengthening of normally hidden subthreshold synaptic inputs.
TL;DR: Correlation of the neuroimaging findings in this case with the most commonly used maps of the representation of the visual field on the striate cortex suggests that none of the maps correctly predicts the location or extent of lesions that affect the intermediate portion of the cortex.
TL;DR: It is demonstrated that sharp and contrast–invariant orientation tuning curves are combined with contrast saturation, the strength of cortical amplification can be localized in orientation space and anisotropic contextual suppression by iso-oriented flanking stimuli arises as an emergent property and can be mediated by local connections.
TL;DR: This work presents a model, based on local intracortical connectivity between cells of similar orientation tuning, that can account for many aspects of cross-orientation inhibition.
13 Jun 2001
TL;DR: It was shown that disinhibitory mechanism could explain neuronal sensitivity to cross-like figures and which combinations of the relative shape, localization and weight of the excitatory, end-stopping and disin inhibitory zones of the simulated receptive field allow to imitate a selective or an invariant tuning to a cross- like figure of the real neurons in the cat primary visual cortex.
Abstract: Sensitivity of simulated striate neurons to the crosses of different shape and orientation was studied in a two-layered neural network which consisted of formal neurons with end-stopping inhibitory and disinhibitory zones in the receptive field. We evaluated the output responses of neurons under variation of a cross size, shape, orientation. It was shown that disinhibitory mechanism could explain neuronal sensitivity to cross-like figures. The tuning of the simulated neurons calculated from their output responses reproduced the characteristic features of the natural units in the cat striate cortex. It was shown which combinations of the relative shape, localization and weight of the excitatory, end-stopping and disinhibitory zones of the simulated receptive field allow to imitate a selective or an invariant tuning to a cross-like figure of the real neurons in the cat primary visual cortex.
21 Aug 2001
TL;DR: A correlation-based model for the orientation map formation proposed by Miller is considered and the result indicates that the developed orientation maps have the following properties: maps have oriented receptive fields and periodicity of phases appears.
Abstract: We consider a correlation based model for the orientation map formation proposed by Miller[3] and study the formation mathematically. We perform the Fourier transform of the model and we observe that the model has the following properties. (1) It develops oriented receptive fields; (2) These oriented receptive fields are arranged in order, and ordered orientation columns are developed; (3) The periodicity of orientations on the cortical surface lacks; (4) The periodicity of phases appears; (5) Singular points appear irregularly on the cortical surface. Our analytical results are justified by computer simulations.
TL;DR: The aim of the present work was to study the distribution of connections running from field 18 to field 17 within the cortical space and the compare their distribution with the distributed connections within field 18.
Abstract: of the cat cerebral cortex is determined by many factors, particularly the characteristics of the distribution of the thalamic inputs and neuronal connections within these fields, between these fields, and with the hemispheres [11–15]. Unlike other cortical fields involved in the processing of visual information, fields 17 and 18 receive afferent fibers from layers A and A1 of the dorsal nucleus of the lateral geniculate body. Thus, processing of visual information in these fields is performed in parallel. In the hierarchical structure of the visual cortical fields, fields 17 and 18 are at the lower levels [14]. Reports describing the structure and functional characteristics of fields 17 and 18 have focused significantly on connections within and between these fields [4–6, 8, 13]. The spatial organization of different types of connection and their relationships are important for understanding the mechanisms by which visual information is processed in the cortical fields. Studies of the internal connections of field 17 have demonstrated that in the plane parallel to the cortical surface, these connections are located along the projection of the horizontal meridian of the visual field [1], while the internal horizontal connections of field 18 are distributed along the projection of the vertical meridian of the visual field [3]. These data led to the conclusion that field 17 performs more detailed analysis of the horizontal components of images, while field 18 is concerned with the analysis of the vertical components. The aim of the present work was to study the distribution of connections running from field 18 to field 17 within the cortical space and the compare their distribution with the distribution of connections within field 18.