Showing papers on "Orientation column published in 2004"
TL;DR: Observing the development of circuits in the rat barrel cortex using laser-scanning photostimulation analysis of synaptic connectivity, reconstructions of axonal arbors, and in vivo whole-cell recording revealed already spatially well-tuned receptive fields.
178 citations
TL;DR: Results from computer simulations show that the "haphazard wiring" model is consistent with data on the probability of monosynaptic connections and generates orientation columns and maps resembling those found in the cortex.
Abstract: The receptive fields of simple cells in visual cortex are composed of elongated on and off subregions. This spatial arrangement is widely thought to be responsible for the generation of orientation...
107 citations
TL;DR: It is hypothesized that columns of neurons that are vertically aligned with the septa, or septal columns, are functionally linked by virtue of their projections to MI cortex and represent an interconnected and functionally distinct circuit that transmits information to MI and other brain regions involved in motor control.
Abstract: In rodents, each mystacial whisker is represented in the granular layer of primary somatosensory (SI) cortex by a compact cluster of cells known as a barrel, and barrels are separated from each other by domains that are called septa. Vertical columns of neurons aligned with each barrel act as a functional assembly to process information from a “principal” whisker, but a functional role has not been identified for vertical columns of neurons that are aligned with the septa. To determine whether these septal columns provide the main source of projections to primary motor (MI) cortex, we placed retrograde tracers in MI cortex and analyzed the location of the retrogradely labeled neurons with respect to the septal and barrel compartments of SI barrel cortex. In cases in which SI barrel cortex was sectioned tangentially, retrogradely labeled neurons in the extragranular layers of SI were plotted and superimposed onto reconstructions of the layer IV barrel field. In each of these cases, most labeled neurons were located above or below the septal regions of layer IV. When SI barrel cortex was sectioned coronally, we observed multiple columns of labeled SI neurons that were vertically aligned with the septal zones of layer IV. These results indicate that columns of neurons that are vertically aligned with the septa, or septal columns, are functionally linked by virtue of their projections to MI cortex. We hypothesize that these septal columns represent an interconnected and functionally distinct circuit that transmits information to MI and other brain regions involved in motor control. J. Comp. Neurol. 480:299 –309, 2004. © 2004 Wiley-Liss, Inc.
67 citations
01 Jan 2004
TL;DR: Research in receptive fields and suppressive fields in lateral geniculate nucleus (LGN) and in primary visual cortex (V1) is summarized and it is hoped that this term will find wide acceptance to describe responses of both LGN and V1 neurons.
Abstract: Initial models proposed that these operations are weighted sums, with weights given by a neuron’s receptive field. These models explain the basic features of response selectivity. They were later extended to explain a number of suppressive effects originating within and outside the region of the receptive field. The resulting models rely on division. In this division, the receptive field feeds into the numerator, and the denominator is provided by a larger, non-classical suppressive field. While the receptive field confers to a neuron the basic selectivity for stimulus properties, the suppressive field modulates responsiveness. A divisive suppressive field confers to neurons in early visual system a number of computational advantages. Recent evidence in higher cortical areas suggests that the modulation of divisive suppression is the primary means of operation of visual attention. In this chapter I summarize research in receptive fields and suppressive fields in lateral geniculate nucleus (LGN) and in primary visual cortex (V1). In the following, I refer to a “suppressive field” as though this term had wide acceptance. In reality, the concept has been proposed only for LGN neurons (Levick et al., 1972), and lies forgotten since 30 years. My hope is that it will find wide acceptance to describe responses of both LGN and V1 neurons. Receptive fields in LGN
60 citations
TL;DR: A simple analysis shows how the responses of V2 neurons to pairs of angled lines may simply sum the responses from one or more orientation selective V1 neurons.
50 citations
TL;DR: The neural circuitry underlying the transformation from non-DS neurons to DS cortical cells is determined, consistent with a linear model whereby DS simple cells are formed from simple-cell inputs, with temporal phase differences often less than quadrature.
Abstract: In the central visual pathway of binocular animals, the property of directional selectivity (DS) is first exhibited in striate cortex. In this study, we sought to determine the neural circuitry underlying the transformation from non-DS neurons to DS cortical cells. In a well established model, DS receptive fields (RFs) are derived from the sum of two non-DS inputs with 90° (quadrature) spatiotemporal phase differences. We explored possible input sources for this model, which include non-DS simple cells and lateral geniculate nucleus (LGN) neurons, by examination of spatiotemporal RFs of single cells and of pairs of cells. We find that distributions of non-DS simple RFs do not match the temporal predictions of the quadrature model because of a lack of long-latency responses. The long-latency inputs could potentially arise from lagged LGN afferents. However, analysis of cell pairs indicates that DS cells receive cortical input from non-DS simple cells for both short- and long-latency components, with temporal phase differences typically90°. Furthermore, the distribution of minimum phase differences needed to generate DS cells overlaps that exhibited by non-DS simple cells. Considered together, these results are consistent with a linear model whereby DS simple cells are formed from simple-cell inputs, with temporal phase differences often less than quadrature.
49 citations
TL;DR: The results indicate a positive feedback from high-order visual cortical area 21a to lower-order areas underlying a spatial frequency-dependent mechanism.
48 citations
TL;DR: It is demonstrated that the integration of local flanking elements with a central stimulus can occur as early as 80 ms in human visual cortex, but this includes processes occurring at longer latencies and appears to involve both striate and extrastriate visual areas.
36 citations
TL;DR: It is demonstrated that functions that oscillate more than once do not produce maps closely resembling those seen biologically, which strongly suggests that local lateral connections in visual cortex oscillate only once and have the form of a Mexican hat.
Abstract: Maps of ocular dominance and orientation in primary visual cortex have a highly characteristic structure. The factors that determine this structure are still largely unknown. In particular, it is unclear how short-range excitatory and inhibitory connections between nearby neurons influence structure both within and between maps. Using a generalized version of a well-known computational model of visual cortical map development, we show that the number of excitatory and inhibitory oscillations in this interaction function critically influences map structure. Specifically, we demonstrate that functions that oscillate more than once do not produce maps closely resembling those seen biologically. This strongly suggests that local lateral connections in visual cortex oscillate only once and have the form of a Mexican hat.
36 citations
TL;DR: The cerebral cortex is organized in minicolumns of output neurons visible at the earliest ages studied (P3), which might have a higher probability of being interconnected than those outside.
Abstract: The apical dendrites of the pyramidal neurons of the cerebral cortex form radial bundles in all species and areas. Using microtubule-associated protein (MAP)2 immunostaining and Voronoi tessellation analysis in the rat visual cortex, we obtained objective criteria to define dendritic bundles in tangential sections: in supragranular layers of the rat visual cortex we found bundles of 6-6.4 dendrites, at a density of 1929 bundles/mm(2) and a centre-to-centre distance of 27 micro m. Using lipophilic tracers to label different pyramidal cell populations, based on the same criteria as in MAP2-immunostained material, we found that in the rat visual cortex the bundles consist of neurons with specific targets. Neurons projecting to the ipsi- or contralateral cortex form bundles together and with neurons projecting to the striatum, but not with those projecting to the superior colliculus, dorsal division of the lateral geniculate nucleus or through the cerebral peduncle. The latter neurons form bundles with neurons projecting to the striatum. Thus, the cerebral cortex is organized in minicolumns of output neurons visible at the earliest ages studied (P3), which might have a higher probability of being interconnected than those outside.
31 citations
TL;DR: Using a model of activity-dependent self-organization of geniculo-cortical afferent inputs, it is shown that spontaneous activity in the LGN can produce orientation maps, while the exposure to drifting gratings results in sharply segregated orientation maps as observed in cat visual cortex.
TL;DR: Electrical microstimulation delivered to primary visual cortex (V1) concurrently with the presentation of visual targets interferes with the selection of these targets and disrupts the flow of visual information along the geniculostriate pathway.
Abstract: Electrical microstimulation delivered to primary visual cortex (V1) concurrently with the presentation of visual targets interferes with the selection of these targets. To determine the source of this interference, we stimulated the visual input layers of V1 as rhesus monkeys generated saccadic eye movements to visual targets presented at and outside the receptive field of the stimulated neurons. Columns of cells in V1 innervated by the left and right eye are segregated according to eye dominance, such that cells within a column respond best to visual stimuli presented to the ocular dominant eye. Interference was maximal when targets were presented to the ocular dominant eye, moderate when presented to the ocular inferior eye, and negligible when presented to both eyes. Thus, electrical microstimulation of the visual input layers of V1 disrupts the flow of visual information along the geniculostriate pathway. Knowing how electrical stimulation of V1 affects visual behaviour is necessary when using monkeys to develop a visual prosthesis for the blind.
01 Jan 2004
TL;DR: It is suggested that columns in field 17 of the cat cortex are associated with 6–8 hyperColumns, though only with a single type of neuron within these hypercolumns, in terms of eye dominance and orientational preference.
Abstract: The spatial distribution of horizontal internal connections in field 17 of the cat cortex was studied after microiontophoretic application of horseradish peroxidase to individual cortical columns. Cluster analysis of the distribution of labeled cells in the superficial layers in the tangential plane of the cortex was performed. Field 17 included 7 ± 1 clusters of up to five cells. Clusters were distributed into two layers, separated by 1.2 ± 0.3 mm. The distance between the centers of the clusters forming rows was 0.8 ± 0.3 mm. The spatial characteristics of the grouping of cells sending axons into the cortical column were compared with published data based on optical visualization of the activity of neurons in orientational and eye-dominant columns of the visual cortex. It is suggested that columns in field 17 are associated with 6–8 hypercolumns, though only with a single type of neuron within these hypercolumns, in terms of eye dominance and orientational preference.
TL;DR: A new study in which activity was simultaneously recorded in pairs of retinal and cortical neurons provides evidence that these pathways converge on a single cortical neuron.
TL;DR: Horseradish peroxidase was applied microiontophoretically to nine individual columns in fields 17 and six columns in field 18 of the cat cerebral cortex, suggesting that the fields studied here contained columns which were afferent in relation to the ipsilateral eye and the contralateral eye.
Abstract: Horseradish peroxidase (HRP) was applied microiontophoretically to nine individual columns in fields 17 and six columns in field 18 of the cat cerebral cortex. Most labeled cells in the dorsal lateral geniculate body were identified in layer A. The ratio of number of labeled cells in layer A to the number of labeled cells in layer A1 was assessed (the A/A1 ratio). Application of HRP to columns in field 17 yielded A/A1 ratios of 0.5 to 2.5; application to field 18 gave ratios ranging from 0.2 to 0.9. This suggests that the fields studied here contained columns which were afferent in relation to the ipsilateral eye and the contralateral eye.
TL;DR: It is hypothesized that inhibitory processes and subthreshold influences from a space surrounding the RF play a special role in the formation of the neuronal responses generated in the associative visual cortical regions to visual stimulation.
Abstract: We studied the responses of neurons of the extrastriate cortical area 21b of the cat to changes in orientation of the movements of visual stimuli within the receptive field (RF) of the neuron under study. Our experiments demonstrated that 24 of 108 cells (22%) responded differentially to a certain extent to orientation of the movements of visual stimuli. As a whole, neurons of the area 21b did not demonstrate fine tuning on the optimum angle of orientation. In many cases, neuronal responses to different orientations of the movement of visual stimulus depended significantly on specific parameters of this stimulus (its shape, dimensions, and contrast). Some directionally sensitive neurons responded to a change in orientation of the movement of visual stimuli by modification of the index of directionality. We also studied spatial organization of the RF of neurons with the presentation of stationary visual stimuli. Comparison of the neuronal responses to a change in orientation of the movements of stimuli and to presentation of stationary stimuli showed that the correlation between the orientation sensitivity of the neuron under study and the stationary functional organization of its RF was insignificant. We hypothesize that inhibitory processes and subthreshold influences from a space surrounding the RF play a special role in the formation of the neuronal responses generated in the associative visual cortical regions to visual stimulation.