11 results
Ocular dominance and disparity coding in cat visual cortex
- Simon LeVay, Thomas Voigt
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- Journal:
- Visual Neuroscience / Volume 1 / Issue 4 / July 1988
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- 02 June 2009, pp. 395-414
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The orientation selectivity, ocular dominance, and binocular disparity tuning of 272 cells in areas 17 and 18 of barbiturate-anesthetized, paralyzed cats were studied with automated, quantitative techniques. Disparity was varied along the axis orthogonal to each cell's best orientation. Binocular correspondence was established by means of a reference electrode positioned at the boundary of lamina A and Al in the area centralis representation of the lateral geniculate nucleus. Measures were derived that expressed each cell's disparity sensitivity and best disparity and the shape and slope of its tuning curve. Cells were found that corresponded to categories described by previous authors (“disparity-insensitive,” “tuned excitatory,” “near,” and “far” cells), but many others had intermediate response patterns, or patterns that were difficult to categorize. Quantitative analysis suggested that the various types belong to a continuum.
No relationship could be established between a cell's best orientation and its ocular dominance or any aspect of its disparity tuning. There was no relationship between a cell's ocular dominance and its sensitivity to disparity. Ocular dominance and best disparity were related. As reported by others, cells with best disparities close to zero (the fixation plane) tended to have balanced ocularity, while cells with best disparities in the near or far range had a broad distribution of ocular dominance. Among cells with receptive fields near the vertical meridian, those preferring far disparities tended to be dominated by the contralateral eye, and those preferring near disparities by the ipsilateral eye. It is suggested that this relationship follows from the geometry of near and far images and the pattern of decussation in the visual pathway. There was a significant grouping of cells with similar best disparities along tangential electrode tracks. We believe that this grouping is due to the columnar organization for ocular dominance and the relationship between ocular dominance and best disparity. No evidence was found for a columnar segregation of disparity-sensitive and disparity-insensitive cells.
Visual responsiveness and direction selectivity of cells in area 18 during local reversible inactivation of area 17 in cats
- C. Casanova, Y. Michaud, C. Morin, P.A. McKinley, S. Molotchnikoff
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- Journal:
- Visual Neuroscience / Volume 9 / Issue 6 / December 1992
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- 02 June 2009, pp. 581-593
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We have investigated the effects of inactivation of localized sites in area 17 on the visual responses of cells in visuotopically corresponding regions of area 18. Experiments were performed on adult normal cats. The striate cortex was inactivated by the injection of nanoliters of lidocaine hydrochloride or of γ-aminobutyric acid (GABA) dissolved in a staining solution. Responses of the simple and complex cells of area 18 to optimally oriented light and dark bars moving in the two directions of motion were recorded before, during, and after the drug injection. Two main effects are described.
First, for a substantial number of cells, the drug injection provoked an overall reduction of the cell's visual responses. This nonspecific effect largely predominated in the complex cell family (76% of the units affected). This effect is consistent with the presence of long-range excitatory connections in the visual cortex.
Second, the inactivation of area 17 could affect specific receptive-field properties of cells in area 18. The main specific effect was a loss of direction selectivity of a number of cells in area 18, mainly in the simple family (more than 53% of the units affected). The change in direction selectivity comes either from a disinhibitory effect in the nonpreferred direction or from a reduction of response in the preferred direction. It is proposed that the disinhibitory effects were mediated by inhibitory interneurones within area 18. In a very few cases, the change of directional preference was associated with a modification of the cell's response profile.
These results showed that the signals from area 17 are necessary to drive a number of units in area 18, and that area 17 can contribute to, or at least modulate, the receptive-field properties of a large number of cells in the parastriate area.
Complex transcallosal interactions in visual cortex
- B.R. Payne, D.R. Siwek, S.G. Lomber
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- Journal:
- Visual Neuroscience / Volume 6 / Issue 3 / March 1991
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- 02 June 2009, pp. 283-287
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Reversible inactivation by cooling of the transcallosal projecting neurons in areas 17 and 18 of one hemisphere bring about complex changes in the spontaneous and evoked activity of neurons in the callosal receiving zone of the opposite hemisphere. These changes include increase and decreases in evoked and spotaneous activities. Overall, 90% of neurons in alyers II and III, 50% in layer IV, and 100% in layers V and VI were affected by the block of transcallosal input. The complexity of the changes was greatest in layers II and III, which are the major callosal recipient layers. The results indicate that many excitatory and inhibitory circuits are under the direct control of transcallosal fibers in the normally fuctioning brain.
Cortical connections of MT in four species of primates: Areal, modular, and retinotopic patterns
- Leah A. Krubitzer, Jon H. Kass
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- Journal:
- Visual Neuroscience / Volume 5 / Issue 2 / August 1990
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- 02 June 2009, pp. 165-204
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Cortical connections were investigated by restricting injections of WGA-HRP to different parts of the middle temporal visual area, MT, in squirrel monkeys, owl monkeys, marmosets, and galagos. Cortex was flattened and sectioned tangentially to facilitate an analysis of the areal patterns of connections. In the experimental cases, brain sections reacted for cytochrome oxidase (CO) or stained for myelin were used to delimit visual areas of occipital and temporal cortex and visuomotor areas of the frontal lobe. Major findings are as follows: (1) The architectonic analysis suggests that in addition to the commonly recognized visual fields, area 17 (V-I), area 18 (V-II), and MT, all three New World monkeys and prosimian galagos have visual areas DL, DI, DM, MST, and FST. (2) Measurements of the size of these areas indicate that about a third of the neocortex in these primates is occupied by the eight visual areas, but they occupy a somewhat larger proportion of neocortex in the diurnal marmosets and squirrel monkeys than the nocturnal owl monkeys and galagos. The diurnal primates also have proportionally more neocortex devoted to areas 17, 18, and DL and less to MT. These differences are compatible with the view that diurnal primates are more specialized for detailed object and color vision. (3) In all four primates, restricted locations in MT receive major inputs from short meandering rows of neurons in area 17 and several bands of neurons in area 18. (4) Major feedforward projections of MT are to two visual areas adjoining the rostral half of MT, areas MST and FST. Other ipsilateral connections are with DL, DI, and in some cases DM, parts of inferotemporal (IT) cortex, and posterior parietal cortex. (5) In squirrel monkeys, where injection sites varied from caudal to rostral MT, caudal parts of MT representing central vision connect more densely to DL and IT than other parts. Both DL and IT cortex emphasize central vision. (6) In the frontal lobe, MT has dense connections with the frontal ventral area (FV), but not with the frontal eye field (FEF). (7) Callosal connections of MT are most dense with matched locations in MT of the other hemisphere, rather than with the outer boundary of MT representing the vertical meridian. Targets of sparser callosal connections include FST, MST, and DL.
The results support the conclusions that (1) prosimian primates and New World monkeys have at least ten visual and visuomotor areas in common, (2) the connections of MT are remarkably consistent across four species of primates, (3) the anatomical segregation of visual subsystems in areas 17 and 18 is common to all primates, (4) connections from the part of MT representing central vision with visual areas emphasizing central vision are more dense, and (5) MT and the associated fields MST and FST occupy proportionally more cortex in nocturnal than diurnal primates.
Cortical connections of area 18 and dorsolateral visual cortex in squirrel monkeys
- C. G. Cusick, J. H. Kaas
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- Journal:
- Visual Neuroscience / Volume 1 / Issue 2 / March 1988
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- 02 June 2009, pp. 211-237
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Cortical connections of area 18 (V-II) and part of the dorsolateral visual area (DL) were determined in squirrel monkeys with single and multiple injections of the sensitive bidirectional tracer, wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). Injections were placed into portions of area 18 or DL on the dorsolateral surface of the brain, patterns of label were examined in brain sections cut parallel to the surface of physically flattened cortex, and comparisons were made with alternate brain sections reacted for cytochrome oxidase (CO) or stained for myelinated fibers. Major results are as follows. (1) Area 18 was identified by a characteristic alternation of dense and light CO bands crossing its width; the middle temporal visual area (MT) was CO dense; the dorsolateral area (DL) was less reactive, with rostral DL (DLR) lighter than caudal DL (DLC); area 17 had clear CO puffs in the supragranular layers. (2) Intrinsic connections revealed in area 18 included a narrow 100–200 μm fringe of less dense label around each injection core, label unevenly distributed in small clumps within 1–2 mm of injection sites, and clumps of transported label up to 6 mm from injection sites. (3) Single and multiple injections in area 18 produced patterns of labeled cells and terminations in area 17 that ranged from lattice- to puff-like in surface-view distribution. With multiple area 18 injections, regions of area 17 could be found where transported label was concentrated in CO puffs, avoided the CO puffs, or overlapped both puff and interpuff divisions of cortex. The labeled regions of area 17 were somewhat larger than the injection sites, suggesting some convergence from area 17 to area 18. (4) The major rostral connections of area 18 were with caudal DL (DLC). Rostral DL (DLR) was largely free of transported label. Single injection sites in area 18 resulted in several large clumps of label separated by regions of sparse or no label in DLC. Injections in lateral area 18 produced lateral foci of label in DL, while more medial injections produced more medial foci. However, following multiple injections into area 18 that included the representation of central vision, a continuous 2–3-mm-wide band of infragranular labeled cells extended from area 18 caudally to MT rostrally in the presumed location of central vision in DLC and DLR. (5) Injections in area 18 produced foci of label in MT. Label was more dorsal in MT with more dorsal injection sites in area 18. (6) Injections in area 18 resulted in sparse label in cortex within the inferior temporal sulcus and in cortex in the location of the frontal eye field. (7) Callosal connections of area 18 were with areas 17, 18, DL, and sparsely with MT. Multiple injections in area 18 produced a narrow, dense strip of label along the contralateral 17/18 border. Most of this label was in area 18, but small protrusions of label extended into area 17, and small separate foci of label were found displaced slightly into area 17. Fingers of callosal connections extended rostrally from the caudal border to cross up to half of the width of medial area 18 and the entire width of lateral area 18 where central vision is represented. Patchy callosal connections were found with DLC. (8) Injections in caudal DL confirmed the observation from area 18 injections that major connections of DLC are with area 18. Injections in DLR produced scattered, small foci of label in area 18 near the rostral border, as well as puffs of intrinsic connections, connections with MT, and with cortex rostral to area 18 medially.
The major conclusion stemming from the present results is that the DL region consists of at least two fields, with the caudal portion, DLC, receiving major inputs from area 18, and the rostral portion, DLR, having little input from area 18.
Area 17 lesions deactivate area MT in owl monkeys
- Jon H. Kaas, Leah A. Krubitzer
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- Journal:
- Visual Neuroscience / Volume 9 / Issue 3-4 / October 1992
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- 02 June 2009, pp. 399-407
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The middle temporal visual area, MT, is one of three major targets of the primary visual cortex, area 17, in primates. We assessed the contribution of area 17 connections to the responsiveness of area MT neurons to visual stimuli by first mapping the representation of the visual hemifield in MT of anesthetized owl monkeys with microelectrodes, ablating an electrophysiologically mapped part of area 17, and then immediately remapping MT. Before the lesions, neurons at recording sites throughout MT responded vigorously to moving slits of light and other visual stimuli. In addition, the relationship of receptive fields to recording sites revealed a systematic representation of the contralateral visual hemifield in MT, as reported previously for owl monkeys and other primates. The immediate effect of removing part of the retinotopic map in area 17 by gentle aspiration was to selectively deactivate the corresponding part of the visuotopic map in MT. Lesions of dorsomedial area 17 representing central and paracentral vision of the lower visual quadrant deactivated neurons in caudomedial MT formerly having receptive fields in the central and paracentral lower visual quadrant. Most neurons at recording sites throughout other parts of MT had normal levels of responsiveness to visual stimuli, and receptive-field locations that closely matched those before the lesion. However, neurons at a few sites along the margin of the deactivated zone of cortex had receptive fields that were slightly displaced from the region of vision affected by the lesion into other parts of the visual field, suggesting some degree of plasticity in the visual hemifield representation in MT. Subsequent histological examination of cortex confirmed that the lesions were confined to area 17 and the recordings were in MT. The results indicate that the visually evoked activity of neurons in MT of owl monkeys is highly dependent on inputs relayed directly or indirectly from area 17.
Depth perception and cortical physiology in normal and innate microstrabismic cats
- C. Distler, K.-P. Hoffmann
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- Journal:
- Visual Neuroscience / Volume 6 / Issue 1 / January 1991
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- 02 June 2009, pp. 25-41
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Evidence is presented that innate microstrabismus and abnormal cortical visual receptive-field properties can occur also in cats without any apparent involvement of the Siamese or albino genetic abnormalities in their visual system. A possible cause for microstrabismus in these cats may be sought in an abnormally large horizontal distance between blind spot and area centralis indicated by a temporal displacement of the most central receptive fields on both retinae.
Depth perception was found to be impaired in cats with innate microstrabismus. Behavioral measurements using a Y-maze revealed in four such cats that the performance in recognizing the nearer of two random-dot patterns did not improve when they were allowed to use both eyes instead of only one. The ability of microstrabismic cats to perceive depth under binocular viewing conditions only corresponded to the monocular performance of five normal cats.
Electrophysiological recordings were performed in the visual cortex (areas 17 and 18) of four awake cats, two normal, and two innate microstrabismic animals. Ocular dominance and orientation tuning of single neurons in area 17 and 18 were analyzed quantitatively.
The percentage of neurons in area 17 and 18 which could be activated through either eye was significantly reduced to 49.7% in the microstrabismic animals when compared to the normal cats (74.8%). “True binocular cells,” which can only be activated by simultaneous stimulation of both eyes, were significantly less frequent (1.6%) in microstrabismic cats than in normal animals (10.4%). However, subthreshold binocular interactions were identical in both groups of animals. In the strabismic animals, long-term binocular stimulation of monocular neurons did not give a clear indication of alternating use of one or the other eye.
The range of stimulus orientations leading to discharge rates above 50% of the maximal response, i.e. the half-width of the orientation tuning curves, was the same in the two groups of cats. However, orientation sensitivity, i.e. the alternation in discharge rate per degree change in stimulus orientation, was higher in cortical cells of normal cats than in those of microstrabismic cats.
In normal and microstrabismic cats, no clear sign of an “oblique effect,” i.e. the preference of cortical neurons for vertical and horizontal orientations compared to oblique orientations, could be found neither in the incidence of cells with horizontal or vertical preferred orientation nor in the sharpness of orientation tuning and sensitivity of these neurons.
In summary, the receptive-field properties reported here for awake innate microstrabismic cats are similar to those reported in the literature for anesthetized cats with varying degrees of albinism and for cats with artificial symmetrical strabismus surgically induced by sectioning the equivalent extraocular muscles in both eyes. Our innate microstrabismic cats may provide, however, an animal model for investigating the etiology of one form of naturally occurring strabismus.
Neuronal response to texture- and contrast-defined boundaries in early visual cortex
- YUNING SONG, CURTIS L. BAKER
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- Journal:
- Visual Neuroscience / Volume 24 / Issue 1 / January 2007
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- 12 April 2007, pp. 65-77
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Natural scenes contain a variety of visual cues that facilitate boundary perception (e.g., luminance, contrast, and texture). Here we explore whether single neurons in early visual cortex can process both contrast and texture cues. We recorded neural responses in cat A18 to both illusory contours formed by abutting gratings (ICs, texture-defined) and contrast-modulated gratings (CMs, contrast-defined). We found that if a neuron responded to one of the two stimuli, it also responded to the other. These neurons signaled similar contour orientation, spatial frequency, and movement direction of the two stimuli. A given neuron also exhibited similar selectivity for spatial frequency of the fine, stationary grating components (carriers) of the stimuli. These results suggest that the cue-invariance of early cortical neurons extends to different kinds of texture or contrast cues, and might arise from a common nonlinear mechanism.
On the velocity tuning of area 18 complex cell responses to moving textures
- ILDIKÓ VAJDA, MARTIN J.M. LANKHEET, TESSA M. van LEEUWEN, WIM A. van de GRIND
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- Journal:
- Visual Neuroscience / Volume 19 / Issue 5 / September 2002
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- 12 November 2002, pp. 651-659
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Unlike simple cells, complex cells of area 18 give a directionally selective response to motion of random textures, indicating that they may play a special role in motion detection. We therefore investigated how texture motion, and especially its velocity, is represented by area 18 complex cells. Do these cells have separable spatial and temporal tunings or are these nonseparable? To answer this question, we measured responses to moving random pixel arrays as a function of both pixel size and velocity, for a set of 63 directionally selective complex cells. Complex cells generally responded to a fairly wide range of pixel sizes and velocities. Variations in pixel size of the random pixel array only caused minor changes in the cells' preferred velocity. For nearly all cells the data much better fitted a model in which pixel size and velocity act separately, than a model in which pixel size and velocity interact so as to keep temporal-frequency sensitivity constant. Our conclusion is that the studied population of special complex cells in area 18 are true motion detectors, rather than temporal-frequency tuned neurons.
Thalamic control of cat lateral suprasylvian visual area: Relation to patchy association projections from area 18
- CHOONGKIL LEE, THEODORE G. WEYAND, JOSEPH G. MALPELI
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- Journal:
- Visual Neuroscience / Volume 15 / Issue 1 / January 1998
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- 01 January 1998, pp. 15-25
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In this study, we examined functional contributions of major subdivisions of the lateral geniculate nucleus to the cat's lateral suprasylvian visual area (LS) in relation to the patchy horizontal distributions of association inputs. Multiple-unit activity driven via the contralateral eye was assessed during reversible blockade of the retinotopically corresponding part of layer A, the C layers as a group, or the medial interlaminar nucleus (MIN). Inactivating each of these targets reduced activity at some cortical sites, with inactivation of layer A having, on average, the largest effect. Activity was rarely abolished by inactivation of a single target, indicating that most LS sites receive multiple inputs. Dependence on layer A was strongly correlated with the horizontal distribution of association inputs from area 18. Closely spaced injections of anatomical tracers into extensive regions of area 18 resulted in patches of terminal label in lateral suprasylvian cortex. Activity inside the patches was relatively dependent on layer A, whereas that outside the patches was not. Dependence on the MIN and layer A were negatively correlated, suggesting that inputs dominated by the MIN and layer A were concentrated in independent sets of patches. These results indicate that the anatomically observed patchy projections reflect the functional consequences of geniculate lamination. The A layers are high-acuity relays, whereas the MIN is probably a specialization for dim-light vision (Lee et al., 1984; Lee et al., 1992). We propose that the partial overlap of inputs dominated by the A layers and the MIN allows dynamic shifts in their relative contributions to LS responses, optimizing the balance of high-acuity and high-sensitivity channels over a wide range of illumination conditions.
Thalamic control of cat area-18 supragranular layers: Simple cells, complex cells, and cells projecting to the lateral suprasylvian visual area
- CHOONGKIL LEE, THEODORE G. WEYAND, JOSEPH G. MALPELI
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- Visual Neuroscience / Volume 15 / Issue 1 / January 1998
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- 01 January 1998, pp. 27-35
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The goal of this study was to determine the effects of inactivating layer A or the C layers of the cat lateral geniculate nucleus on the supragranular layers of area 18, including cells antidromically activated from the lateral suprasylvian visual area (LS). Isolated cells were visually driven via the contralateral eye while the retinotopically corresponding regions of layer A or, in some cases, the C layers were reversibly inactivated with injections of cobaltous chloride. Simple cells were frequently encountered and were on average more dependent upon layer A than were complex cells, a result qualitatively similar to that found previously in area 17 (Malpeli, 1983; Malpeli et al., 1986). However, the influence of the C layers on area 18 was much more apparent than for area 17. In area 18, as in area 17, the dependence of simple cells on particular geniculate layers appears to follow the terminal patterns of the major direct geniculate inputs. Those simple cells most dependent on layer A were located in lower layer 3. Simple cells in upper layer 3, like complex cells, showed little dependence on layer A, but were strongly dependent upon the C layers. All cells antidromically activated from LS were simple cells with rapidly conducting axons. They had, on average, the same moderately strong dependence on layer A as the patches of LS receiving area 18 input (Lee et al., 1997), supporting the conclusion that the influence of layer A in these patches is largely transmitted via association inputs from area 18. These results demonstrate that simple cells play a major role in association pathways.