Showing papers on "Orientation column published in 2000"
TL;DR: In ferrets in which retinal projections are routed into the auditory pathway, visually responsive neurons in ‘rewired’ primary auditory cortex are also organized into orientation modules, showing that afferent activity has a profound influence on diverse components of cortical circuitry, including thalamocortical and local intracortical connections, which are involved in the generation of orientation tuning, and long-range horizontal connections which are important in creating an orientation map.
Abstract: Modules of neurons sharing a common property are a basic organizational feature of mammalian sensory cortex. Primary visual cortex (V1) is characterized by orientation modules—groups of cells that share a preferred stimulus orientation—which are organized into a highly ordered orientation map. Here we show that in ferrets in which retinal projections are routed into the auditory pathway, visually responsive neurons in ‘rewired’ primary auditory cortex are also organized into orientation modules. The orientation tuning of neurons within these modules is comparable to the tuning of cells in V1 but the orientation map is less orderly. Horizontal connections in rewired cortex are more patchy and periodic than connections in normal auditory cortex, but less so than connections in V1. These data show that afferent activity has a profound influence on diverse components of cortical circuitry, including thalamocortical and local intracortical connections, which are involved in the generation of orientation tuning, and long-range horizontal connections, which are important in creating an orientation map.
433 citations
TL;DR: A biphasic BOLD response to visual stimulation in the primary visual cortex of cats is reported, indicating the pattern of overall activation in the visual cortex, but were less suited to discriminate active from inactive columns.
Abstract: Blood-oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is an important tool for localizing brain functions in vivo. However, the ability of BOLD fMRI to map cortical columnar structures is highly controversial, as the ultimate functional specificity of BOLD remains unknown. Here we report a biphasic BOLD response to visual stimulation in the primary visual cortex of cats. In functional imaging, the initial BOLD signal decrease accurately labeled individual isoorientation columns. In contrast, the delayed positive BOLD changes indicated the pattern of overall activation in the visual cortex, but were less suited to discriminate active from inactive columns.
390 citations
TL;DR: Functional magnetic resonance imaging (fMRI) was used to measure an asymmetry in the responses of human primary visual cortex (V1) to oriented stimuli and found that neural responses in V1 were larger for cardinal stimuli than for oblique stimuli.
Abstract: Visual perception critically depends on orientation-specific signals that arise early in visual processing Humans show greater behavioral sensitivity to gratings with horizontal or vertical (0 degrees /90 degrees; 'cardinal') orientations than to other, 'oblique' orientations Here we used functional magnetic resonance imaging (fMRI) to measure an asymmetry in the responses of human primary visual cortex (V1) to oriented stimuli We found that neural responses in V1 were larger for cardinal stimuli than for oblique (45 degrees /135 degrees ) stimuli Thus the fMRI pattern in V1 closely resembled subjects' behavioral judgments; responses in V1 were greater for those orientations that yielded better perceptual performance
350 citations
TL;DR: An explanation for how selectivity for orientation could be produced by a model with circuitry that is based on the anatomy of V1 cortex, a network model of layer 4Calpha in macaque primary visual cortex, which obtains sharpening, diversity in selectivity, and dynamics of orientation selectivity.
Abstract: In this paper, we offer an explanation for how selectivity for orientation could be produced by a model with circuitry that is based on the anatomy of V1 cortex. It is a network model of layer 4Cα in macaque primary visual cortex (area V1). The model consists of a large number of integrate-and-fire conductance-based point neurons, both excitatory and inhibitory, which represent dynamics in a small patch of 4Cα—1 mm2 in lateral area—which contains four orientation hypercolumns. The physiological properties and coupling architectures of the model are derived from experimental data for layer 4Cα of macaque. Convergent feed-forward input from many neurons of the lateral geniculate nucleus sets up an orientation preference, in a pinwheel pattern with an orientation preference singularity in the center of the pattern. Recurrent cortical connections cause the network to sharpen its selectivity. The pattern of local lateral connections is taken as isotropic, with the spatial range of monosynaptic excitation exceeding that of inhibition. The model (i) obtains sharpening, diversity in selectivity, and dynamics of orientation selectivity, each in qualitative agreement with experiment; and (ii) predicts more sharpening near orientation preference singularities.
265 citations
TL;DR: The hypothesis that nerve cells in middle layers of the cortex should be joined by narrow vertical connections to cells in layers lying superficial and deep to them, so that all cells in the column are excited by incoming stimuli with only small latency differences is formulated.
Abstract: Neuroanatomists from Cajal on (1) have searched in the cerebral cortex for units of structural organization that transcend the laminar pattern visible even to the untutored eye in Nissl-stained preparations. Many have commented on the vertical column-like arrays of cell bodies running orthogonal to the horizontal laminae that are particularly conspicuous in the temporal cortex of humans and other primates (Fig. 1). These columns have been promoted in the past as the morphological correlates of the functional columnarity of the cortex, known from physiological studies (2). The hypothesis of the column as the fundamental processing unit of the cerebral cortex was formulated by Mountcastle (3) from studies of cells responding to tactile stimuli in the somatosensory cortex of the cat. The hypothesis requires that nerve cells in middle layers of the cortex, in which thalamic afferents terminate, should be joined by narrow vertical connections to cells in layers lying superficial and deep to them, so that all cells in the column are excited by incoming stimuli with only small latency differences. The columns form a series of repeating units across the horizontal extent of the cortex.
Figure 1
Nissl-stained section of the upper bank of the superior temporal sulcus from a human brain, showing microcolumns of nerve cells (×40).
The verticality of cell–cell connections in the cortex has never been in doubt, but determining the minimal unit of such connectivity and the extent to which it is based on morphologically definable arrays of cells continues to exercise investigators. One problem inherent in the different experimental models customarily invoked as demonstrative of cortical columns is that they differ in scale. A column defined by neurons responding to peripheral stimulation as a vertically oriented microelectrode descends through the cortical layers, is narrower than the layer IV barrels of the rodent somatosensory cortex, and the …
226 citations
TL;DR: The main findings were that LGN cells on average process color information linearly, exhibiting sinusoidal changes in firing rate to isoluminant stimuli that vary sinusoidally in cone contrast as a function of color angle, and that the contribution of the S-opponent path is doubled at the level of the striate cortex, relative to that at the LGN.
Abstract: We have recorded the responses of single cells in the lateral geniculate nucleus (LGN) and striate cortex of the macaque monkey. The response characteristics of neurons at these successive visual processing levels were examined with isoluminant gratings, cone-isolating gratings, and luminance-varying gratings. The main findings were: (i) Whereas almost all parvo- and konio-cellular LGN cells are of just two opponent-cell types, either differencing the L and M cones (Lo and Mo cells), or the S vs. L + M cones (So cells), relatively few striate cortex simple cells show chromatic responses along these two cardinal LGN axes. Rather, most are shifted away from these LGN chromatic axes as a result of combining the outputs (or the transformed outputs) of So with those of Lo and/or Mo cells. (ii) LGN cells on average process color information linearly, exhibiting sinusoidal changes in firing rate to isoluminant stimuli that vary sinusoidally in cone contrast as a function of color angle. Some striate cortex simple cells also give linear responses, but most show an expansive response nonlinearity, resulting in narrower chromatic tuning on average at this level. (iii) There are many more +So than −So LGN cells, but at the striate cortex level −So input to simple cells is as common as +So input. (iv) Overall, the contribution of the S-opponent path is doubled at the level of the striate cortex, relative to that at the LGN.
185 citations
TL;DR: In these early stages of the visual system, attention to the orientation of the grating suppressed the metabolic activity in a retinotopically specific band peripheral to the representation of the stimulus.
Abstract: In this study we used a modified double-label deoxyglucose procedure to investigate attention-dependent modulations of deoxyglucose uptake at the earliest stages of the macaque visual system. Specifically, we compared activity levels evoked during two tasks with essentially identical visual stimulation requiring different attentional demands. During a featural-attention task, the subjects had to discriminate the orientation of a grating; during a control spatial-attention task, they had to localize the position of a target point. Comparison of the resulting activity maps revealed attention-dependent changes in metabolic activity in portions of the magnocellular layers of the lateral geniculate nucleus, and the magnocellular-recipient layers 4Calpha and 4B of the striate cortex. In these early stages of the visual system, attention to the orientation of the grating suppressed the metabolic activity in a retinotopically specific band peripheral to the representation of the stimulus. These results favor an early selection model of attention. After a thalamic attention-dependent gating mechanism, irrelevant visual information outside the focus of attention may be suppressed at the level of the striate cortex, which would then result in an increased signal-to-noise ratio for the processing of the attended feature in higher-tier, less retinotopically organized, extrastriate visual areas.
161 citations
TL;DR: A substantial number of neurons with bilateral receptive fields on hand digits, shoulders-arms or legs-feet in the caudalmost part of the postcentral gyrus in awake Japanese monkeys (Macaca fuscata) are found, which is a new interpretation to the midline fusion theory.
Abstract: Earlier studies recording single neuronal activity with bilateral receptive fields in the primary somatosensory cortex of monkeys and cats agreed that the bilateral receptive fields were related exclusively to the body midline and that the ipsilateral information reaches the cortex via callosal connections since they are dense in the cortical region representing the midline structures of the body while practically absent in the regions representing the distal extremities. We recently found a substantial number of neurons with bilateral receptive fields on hand digits, shoulders–arms or legs–feet in the caudalmost part (areas 2 and 5) of the postcentral gyrus in awake Japanese monkeys ( Macaca fuscata ). I review these results, discuss the functional implications of this bilateral representation in the postcentral somatosensory cortex from a behavioural standpoint and give a new interpretation to the midline fusion theory.
144 citations
TL;DR: The data suggest that the strongest input to cortical cells will arise from geniculate cells representing areas of visual space located at the borders of a visual stimulus, and suggests that analysis of response properties by patterns centred over the receptive fields of cells may give a misleading impression of the process of the representation.
Abstract: We have compared the spatial summation characteristics of cells in the primary visual cortex with those of cells in the dorsal lateral geniculate nucleus (LGN) that provide the input to the cortex. We explored the influence of varying the diameter of a patch of grating centred over the receptive field and quantitatively determined the optimal summation diameter and the degree of surround suppression for cells at both levels of the visual system using the same stimulus parameters. The mean optimal summation size for LGN cells (0.90°) was much smaller than that of cortical cells (3.58°). Virtually all LGN cells exhibited strong surround suppression with a mean value of 74%±1.61% SEM for the population as a whole. This potent surround suppression in the cells providing the input to the cortex suggests that cortical cells must integrate their much larger summation fields from the low firing rates associated with the suppression plateau of the LGN cell responses. Our data suggest that the strongest input to cortical cells will arise from geniculate cells representing areas of visual space located at the borders of a visual stimulus. We suggest that analysis of response properties by patterns centred over the receptive fields of cells may give a misleading impression of the process of the representation. Analysis of pattern terminations or salient borders over the receptive field may provide much more insight into the processing algorithms involved in stimulus representation.
94 citations
TL;DR: The feedback projections from area 21a appear to exert mainly an excitatory influence on the background activity and responsiveness of area 17 cells and only in subgroups of Area 17 cells does the feedback activity originating from area 20a seem to modulate specifically certain receptive field properties.
Abstract: We have examined the influence of 'feedback' projections from extrastriate visual cortical area 21a on the responses of neurons in area 17 of the cat, by cooling area 21a to 5-10 degrees C while the temperature over the recording sites was kept at 36 degrees C. Orientation, direction and length selectivities as well as contrast sensitivity were tested before and during cooling and after rewarming of area 21a. Overall, for the sample of cells recorded from the part of area 17 visuotopically corresponding to area 21a, the 'spontaneous' activity (at background illumination of 1 cd/m(2)) and the responsiveness to visual stimuli of standard contrast (15) were significantly reduced by inactivation of area 21a. In about half of the cells inactivation of area 21a affected substantially the sharpness of orientation-tuning. However, only in a minority of the cells were the direction or length selectivities significantly affected by inactivation of area 21a. Thus (i) the feedback projections from area 21a appear to exert mainly an excitatory influence on the background activity and responsiveness of area 17 cells and (ii) only in subgroups of area 17 cells does the feedback activity originating from area 21a appear to modulate specifically certain receptive field properties.
80 citations
TL;DR: By coordinating the activity in the two hemispheres in a way that preserves nearest neighbor relationships, callosal connections may best be viewed as elements of local circuits that operate within a single bilateral representation of visual space.
Abstract: Although callosal connections have been shown to link extensive regions of primary visual cortex, the distribution of these connections with respect to the map of visual space and the map of orientation preference remains unclear. Here we combine optical imaging of intrinsic signals with injection of fluorescent microspheres to assess the functional specificity of callosal connections in the tree shrew. By imaging both hemispheres simultaneously while presenting a series of spatially restricted stimuli, we find that a substantial region of visual space is represented bilaterally. Each hemisphere includes a representation of the ipsilateral visual field that is highly compressed relative to that of the contralateral visual field and is most extensive in the lower visual field, where approximately 30(o) of central visual space are represented bilaterally. Callosal connections extend throughout the region of bilateral representation but terminate in a spatially restricted manner that links visuotopically corresponding sites in the two hemispheres. In contrast, callosal connections appear to terminate without regard for the map of orientation preference, showing little sign of the orientation-specific modular and axial specificity that is characteristic of long-range horizontal connections. By coordinating the activity in the two hemispheres in a way that preserves nearest neighbor relationships, callosal connections may best be viewed as elements of local circuits that operate within a single bilateral representation of visual space.
TL;DR: Cytoarchitectural analysis confirmed the identity of area prostriata and further clarified its extent and borders with the parasubiculum of the hippocampal formation rostrally, and V1 of the visual cortex caudally.
Abstract: Area prostriata is a poorly understood cortical area located in the anterior portion of the calcarine sulcus. It has attracted interest as a separate visual area and progenitor for the cortex of this modality. In this report we describe a direct projection from area prostriata to the rostral cingulate motor cortex (M3) that forms the fundus and lower bank of the anterior part of the cingulate sulcus. Injections of retrograde tracers in M3 resulted in labeled neurons in layers III, V and VI of prostriate cortex. However, injections of anterograde tracers in M3 did not demonstrate axon terminals in area prostriata. This connection was organized topographically such that the rostral part of M3 received input from the dorsal region of prostriate cortex, whereas middle and caudal levels of M3 received input from more ventral locations. Injections of retrograde and anterograde tracers in the caudal cingulate motor cortex (M4) did not produce labeling in prostriate cortex. Cytoarchitectural analysis confirmed the identity of area prostriata and further clarified its extent and borders with the parasubiculum of the hippocampal formation rostrally, and V1 of the visual cortex caudally. This linkage between cortex bordering V1 and cortex giving rise to a component of the corticofacial and corticospinal pathways demonstrates a more direct visuomotor route than visual association projections coursing laterally.
TL;DR: The results demonstrate that M. domestica possess a highly differentiated neocortex with clear functional and architectonic cortical field boundaries, as well as discrete patterns of cortical connections.
Abstract: We examined the internal organization and connections of the primary visual area, V1, in the South American marsupial Monodelphis domestica. Multiunit electrophysiological recording techniques were used to record from neurons at multiple sites. Receptive field location, size, progressions, and reversals were systematically examined to determine the visuotopic organization of V1 and its boundaries with adjacent visual areas. As in other mammals, a virtually complete representation of the visual hemifield was observed in V1, which was coextensive with a region of dense myelination. The vertical meridian was represented at the rostrolateral boundary of the field, the upper visual quadrant was represented caudolaterally, whereas the lower visual quadrant was represented rostromedially. Injections of fluorescent tracers into V1 revealed dense connections with cortex immediately adjacent to the rostrolateral boundary, in peristriate cortex (PS or V2). Connections were also consistently observed with a caudotemporal area (CT), entorhinal cortex (EC), and multimodal cortex (auditory/visual, A/V). These results demonstrate that M. domestica possess a highly differentiated neocortex with clear functional and architectonic cortical field boundaries, as well as discrete patterns of cortical connections. Some connections of V1 are similar to those observed in eutherian mammals, such as connections with V2 and extrastriate areas (e.g., CT), which suggests that there are general features of visual system organization that all mammals possess due to retention from a common ancestor. On the other hand, connections of V1 with EC and multimodal cortex may be a primitive feature of visual cortex that was lost in some lineages, may be a derived feature of marsupial neocortex, or may be a feature particular to mammals with small brains.
TL;DR: Analysis of the development and structure of orientation (OR) and ocular dominance maps in the primary visual cortex of cats and monkeys using the elastic net algorithm suggests that developmental order can be predicted from the final OR and OD periodicities.
Abstract: The development and structure of orientation (OR) and ocular dominance (OD) maps in the primary visual cortex of cats and monkeys can be modelled using the elastic net algorithm, which attempts to find an 'optimal' cortical representation of the input features. Here we analyse this behaviour in terms of parameters of the feature space. We derive expressions for the OR periodicity, and the first bifurcation point as a function of the annealing parameter using the methods of Durbin et al (Durbin R, Szeliski R and Yuille A 1989 Neural Computation 1 348-58). We also investigate the effect of the relative order of OR and OD development on overall map structure. This analysis suggests that developmental order can be predicted from the final OR and OD periodicities. In conjunction with experimentally measured values for these periodicities, the model predicts that (i) in normal macaques OD develops first, (ii) in normal cats OR develops first and (iii) in strabismic cats OD develops first.
TL;DR: This study examines the arrangement of orientation pinwheel centers in the cat visual cortex by optical imaging of intrinsic signals and suggests that the areal border imposes a strong restriction on the pattern formation of orientation preference maps in the visual cortex.
Abstract: In the primary visual cortex of higher mammals, orientation preferences are represented continuously except for singular points, so-called pinwheel centers. In spite of the uniqueness of orientation pinwheel centers, very little is known about the pattern of their arrangement. In this study we examined the arrangement of orientation pinwheel centers in the cat visual cortex by optical imaging of intrinsic signals. Our results demonstrate that orientation pinwheel centers are arranged in a unique geometric pattern around the area 17/18 transition zone: pinwheel centers of the same type are arranged in rows parallel to the transition zone, and rows of clockwise and counterclockwise pinwheel centers are arranged alternately. We suggest that the areal border imposes a strong restriction on the pattern formation of orientation preference maps in the visual cortex.
TL;DR: The organization of neocortex in the short-tailed opossum was explored with multiunit microelectrode recordings from middle layers of cortex, revealing the presence of at least two systematic representations of the contralateral body surface located in a continuous strip of cortex running from the rhinal sulcus to the medial wall.
Abstract: The organization of neocortex in the short-tailed opossum ( Monodelphis domestica ) was explored with multiunit microelectrode recordings from middle layers of cortex. Microelectrode maps were subsequently related to the chemoarchitecture of flattened cortical preparations, sectioned parallel to the cortical surface and processed for either cytochrome oxidase (CO) or NADPH-diaphorase (NADPHd) histochemistry. The recordings revealed the presence of at least two systematic representations of the contralateral body surface located in a continuous strip of cortex running from the rhinal sulcus to the medial wall. The primary somatosensory area (S1) was located medially while secondary somatosensory cortex (S2) formed a laterally located mirror image of S1. Auditory cortex was located in lateral cortex at the caudal border of S2, and some electrode penetrations in this area responded to both auditory and somatosensory stimulation. Auditory cortex was outlined by a dark oval visible in flattened brain sections....
TL;DR: A proposed computational model of a dot-pattern selective neuron found in the inferotemporal cortex of monkeys is capable of explaining the results of neurophysiological experiments as well as certain psychophysical observations.
Abstract: A computational model of a dot-pattern selective neuron is proposed. This type of neuron is found in the inferotemporal cortex of monkeys. It responds strongly to groups of dots and spots of light intensity variation but very weakly or not at all to single dots and spots that are not part of a pattern. This non-linear behaviour is quite different from the spatial frequency filtering behaviour exhibited by other neurons that react to spot-shaped stimuli, such as neurons with centre-surround receptive field profiles found in the lateral geniculate nuclei and layer 4Cβ of V1. It is implemented in the proposed computational model by using an AND-type non-linearity to combine the responses of centre-surround cells. The proposed model is capable of explaining the results of neurophysiological experiments as well as certain psychophysical observations.
TL;DR: It is hypothesize that a small and anatomically undetectable imbalance between the afferents from the two eyes is amplified by intracortical interactions so that their activity patterns become different and may guide the segregation process of the Afferents in cortical layer IV.
Abstract: During postnatal development of the visual cortex the thalamocortical afferents serving the two eyes segregate into alternating patches called ocular dominance (OD) columns. Interested in the dynamics of this segregation process we studied the appearance of functional OD columns in the primary visual cortex of normally raised and strabismic kittens aged 2-6 weeks using 2-deoxyglucose labelling in awake animals. In both experimental groups, OD columns covering the entire area 17 and spanning all cortical laminae are first visible at 3 weeks and appear already adult-like at 4 weeks, much earlier than thought on the basis of previous anatomical studies. We hypothesize that a small and anatomically undetectable imbalance between the afferents from the two eyes is amplified by intracortical interactions so that their activity patterns become different and may guide the segregation process of the afferents in cortical layer IV.
TL;DR: A single-cell model using ON and OFF channels, a natural scene environment, and synaptic modification according to the Bienenstock, Cooper, and Munro (BCM) theory indicates that lateral geniculate nucleus cells must act predominantly in the linear region around the level of spontaneous activity, to lead to the observed segregation of ON/OFF subfields.
Abstract: The receptive fields for simple cells in visual cortex show a strong preference for edges of a particular orientation and display adjacent excitatory and inhibitory subfields. These subfields are projections from ON-center and OFF-center lateral geniculate nucleus cells, respectively. Here we present a single-cell model using ON and OFF channels, a natural scene environment, and synaptic modification according to the Bienenstock, Cooper, and Munro (BCM) theory. Our results indicate that lateral geniculate nucleus cells must act predominantly in the linear region around the level of spontaneous activity, to lead to the observed segregation of ON/OFF subfields.
TL;DR: The finding confirms that the anterior striate cortex, where the monocular temporal crescent is represented, is primarily monocular, but the fact that greatest density of retinal ganglion cells and photoreceptors is in the nasal hemiretina must also be taken into account when interpreting these results.
TL;DR: This model captures the basic geometry and temporal structure of the visual cortex and has been shown to generate propagating waves of activity that contain information about a moving stimulus.
TL;DR: The findings of two patients demonstrate that the horizontal meridian is represented at the calcarine fissure base in the primary visual cortex.
Abstract: The authors report the findings of two patients that confirm the location of the horizontal meridian in the human visual cortex. The first patient had an inferior quadrant defect with a band of horizontal meridian sparing. Magnetic resonance imaging showed a lesion concentrated along the medial striate cortex. The second patient had a homonymous horizontal defect that resulted from removal of an arteriovenous malformation located in the lateral striate cortex. The findings of these two patients demonstrate that the horizontal meridian is represented at the calcarine fissure base in the primary visual cortex.
TL;DR: Analysis of 2-deoxyglucose labeled patterns of orientation domains in area 17 of cat visual cortex identifies sensitive quantitative indicators for the overall similarity and dissimilarity of cortical orientation maps and confirms their strong interindividual variability.
Journal Article•
TL;DR: The optical imaging based on intrinsic signals is the one with the best spatial resolution among in vivo brain imaging techniques and is suitable for studying functional organization of other cortex.
Abstract: The optical imaging based on intrinsic signals is the one with the best spatial resolution among in vivo brain imaging techniques It becomes a powerful tool for studying fuctional architecture of the cortex in a large scale We describe the method using this technique to show the orientation columns in the cat visual cortex Basically, it is also suitable for studying functional organization of other cortex
01 Jan 2000
TL;DR: The proposed model provides a prototype for edge detection using electronic optical techniques and artificial neural nets and its detection capability is comparable to that of the advanced edge detection algorithms of the smoothing spacial differentiation type in vogue.
Abstract: Based on the Gabor function model of simple cortical cells,by imitating the structure of orientation columns in visual cortex, and aided by pattern enhancement and processing nets, a model for edge detection with neuron like organization is constructed. Simulation results show that its detection capability is comparable to that of the advanced edge detection algorithms of the smoothing spacial differentiation type in vogue. It is shown that this model as intuitively based on the early concept of edge detectors is essentially identical in the underlying mechanism to the latter. The proposed model provides a prototype for edge detection using electronic optical techniques and artificial neural nets.
01 Jan 2000
TL;DR: Evidence to the curved model is provided by the fact that the number of pinwheels is shown to stay non-zero in coincidence with finding in animals though in contrast to other models.
Abstract: High-dimensional models of pattern formation in visual cortex can be replaced by low-dimensional feature models provided that relations among the features reflect the high-dimensional structure. We consider orientation columns in a simplified flat high-dimensional setting and show that an exact derivation of a Riemannian-curved low-dimensional model is possible. Further evidence to the curved model is provided by the fact that the number of pinwheels is shown to stay non-zero in coincidence with finding in animals though in contrast to other models.
TL;DR: A geometrical computer model was used to study the dynamics of double orientation tuning of visual cortex neurons, which occurs in the visual cortex of the cat, and showed that acute and selective orientation tuning with two peaks could be formed dynamically only by means of changes in the weightings of zones in a receptive field containing terminal and lateral inhibitory zones.
Abstract: A geometrical computer model was used to study the dynamics of double orientation tuning of visual cortex neurons, which occurs in the visual cortex of the cat. Modeling confirmed the role of the shapes, relative positions, and weightings of the excitatory and inhibitory zones of the receptive field and the dynamics of these properties for generating this effect. It was shown that acute and selective orientation tuning with two peaks could be formed dynamically only by means of changes in the weightings of zones in a receptive field containing terminal and lateral inhibitory zones, while changes in the positions and areas of zones in the receptive field required the receptive field to contain only a terminal inhibitory zone.