Showing papers on "Orientation column published in 1983"

Clustered intrinsic connections in cat visual cortex

Abstract: The intrinsic connections of the cortex have long been known to run vertically, across the cortical layers. In the present study we have found that individual neurons in the cat primary visual cortex can communicate over suprisingly long distances horizontally (up to 4 mm), in directions parallel to the cortical surface. For all of the cells having widespread projections, the collaterals within their axonal fields were distributed in repeating clusters, with an average periodicity of 1 mm. This pattern of extensive clustered projections has been revealed by combining the techniques of intracellular recording and injection of horseradish peroxidase with three- dimensional computer graphic reconstructions. The clustering pattern was most apparent when the cells were rotated to present a view parallel to the cortical surface. The pattern was observed in more than half of the pyramidal and spiny stellate cells in the cortex and was seen in all cortical layers. In our sample, cells made distant connections within their own layer and/or within another layer. The axon of one cell had clusters covering the same area in two layers, and the clusters in the deeper layer were located under those in the upper layer, suggesting a relationship between the clustering phenomenon and columnar cortical architecture. Some pyramidal cells did not project into the white matter, forming intrinsic connections exclusively. Finally, the axonal fields of all our injected cells were asymmetric, extending for greater distances along one cortical axis than along the orthogonal axis. The axons appeared to cover areas of cortex representing a larger part of the visual field than that covered by the excitatory portion of the cell9s own receptive field. These connections may be used to generate larger receptive fields or to produce the inhibitory flanks in other cells9 receptive fields.

Neuronal Operations in the Visual Cortex

Abstract: 1 The Visual System of Cat and Monkey Compared.- 1.1 The Basic Layout of the Visual System in Cat, Owl Monkey, and Rhesus Monkey.- 1.1.1 The Retina.- 1.1.2 The Optic Chiasm and Optic Tract.- 1.1.3 The Dorsal Lateral Geniculate Nucleus (dLGN).- 1.1.4 Visual Cortex.- 1.1.5 Pulvinar.- 1.1.6 Callosal Connections.- 1.2 Quantitative Aspects of the Retino-Geniculo-Cortical Projections.- 1.2.1 The Overall Numbers of Cells in the Visual Pathway.- 1.2.2 Distribution of Retinal Cell Populations.- 1.2.3 Magnification Factors.- 1.3 Conclusion.- 2 The Visual Cortical Areas of the Cat.- 2.1 Description of the Visual Cortical Areas.- 2.1.1 Area 17: The Prototype of Visual Cortical Areas.- 2.1.2 Areas 18 and 19.- 2.1.3 The Lateral Suprasylvian Areas.- 2.1.4 Areas 20 and 21.- 2.1.5 Additional Visual Areas?.- 2.2 The Levels of Processing in the Visual Cortical System of the Cat.- 2.3 Additional Observations on the Retinotopic Organization in the Primary Complex.- 2.3.1 Variability of the 3 Cortical Maps.- 2.3.2 RF Scatter.- 2.3.3 The 17-18 Border and the Question of the Naso-Temporal Overlap.- 2.3.4 The 18-19 Border and the Question of the Visual Field Islands.- 2.4 Conclusion.- 3 Afferent Projections to Areas 17, 18, 19 of the Cat: Evidence for Parallel Input.- 3.1 The Relay of Retinal Afferents: The Dorsal Lateral Geniculate Nuclear Complex.- 3.2 The Geniculocortical Projection.- 3.3 Functional Streams in the Retino-Geniculocortical Projection.- 3.3.1 Functional Properties of Retinal and Geniculate X, Y, W Cells.- 3.3.2 Correlation with Retinal Morphology.- 3.3.3 Separation of Functional Streams at LGN Level.- 3.3.4 Correlation with LGN Morphological Types.- 3.3.5 Distribution of Functional Streams in dLGN Nuclear Complex.- 3.3.6 Input to Different Areas of Primary Visual Complex.- 3.4 Physiological Identification of the Functional Type of Afferents to Areas 17, 18 and 19.- 3.5 The Termination of Geniculate Afferents in the Visual Cortex.- 3.6 Other Subcortical Afferents: Pulvinar-Lateralis Posterior Complex, Intralaminar Nuclei, Claustrum, and Brainstem.- 3.7 The Ipsilateral Corticocortical Connections.- 3.8 The Connections Through the Corpus Callosum.- 3.9 Conclusion.- 4 Receptive Field Organization in Areas 17, 18 and 19 of the Cat.- 4.1 Twenty Years with the Simple-Complex-Hypercomplex Scheme.- 4.2 Criteria for Classifying Cortical RFs.- 4.2.1 The ON-OFF Overlap or the Parcellation of the RF into Subregions.- 4.2.2 Position Test.- 4.2.3 RF Dimensions.- 4.2.4 End-Stopping or the Hypercomplex Property.- 4.3 The A, B, C, S Scheme.- 4.3.1 Properties and Distribution of Cell Types.- 4.3.2 The S and A Families.- 4.3.3 Responses to Other Stimuli.- 4.4 Correspondence of the A, B, C, S Scheme with Other Classification Schemes.- 4.5 Conclusion.- 5 Parameter Specificity of Visual Cortical Cells and Coding of Visual Parameters.- 5.1 The Tuned Cells as Bandpass Filters: The Multichannel Representation of a Parameter.- 5.2 Are All Tuned Cells Simple (Passive) Bandpass Filters or Are Some of Them Active Filters?.- 5.3 Cells with Thresholds as High-Pass Filters: Single or Multichannel Representation of a Parameter.- 5.4 Conclusion.- 6 Influence of Luminance and Contrast on Cat Visual Cortical Neurons.- 6.1 Contrast-Response Curves Obtained with Sinusoidal Gratings.- 6.2 Contrast-Response Curves Obtained with Slits.- 6.3 The Extreme Contrast Sensitivity at the 18-19 Border.- 6.4 Influence of Contrast and Luminance on Other Response Properties.- 6.5 Conclusion.- 7 Coding of Spatial Parameters by Cat Visual Cortical Neurons: Influence of Stimulus Orientation, Length, Width, and Spatial Frequency.- 7.1 Orientation Tuning of Cortical Cells.- 7.1.1 Definitions and Criteria.- 7.1.2 Quantitative Determinations: Orientation-Response Curves.- 7.1.3 Qualitative Determination: Hand-Plotting.- 7.1.4 Distribution of Preferred Orientations.- 7.1.5 Orientation Columns.- 7.1.6 Conclusion.- 7.2 Influence of Stimulus Length on Cortical Cells.- 7.3 Selectivity of Cortical Neurons for Spatial Frequency and Stimulus Width.- 7.3.1 Selectivity for Spatial Frequency.- 7.3.2 Spatial Frequency and Coding of Stimulus Dimensions.- 7.3.3 Linearity of Cortical Cells.- 7.3.4 The Visual Cortex as a Fourier Analyzer.- 7.3.5 Spatial Frequency: Conclusion.- 7.4 Spatial Parameters: Conclusion.- 8 Coding of Spatio-Temporal Parameters by Cat Visual Cortical Neurons: Influence of Stimulus Velocity Direction and Amplitude of Movement.- 8.1 Influence of Stimulus Velocity.- 8.2 Influence of the Direction of Movement.- 8.3 Influence of Stimulus Movement Amplitude.- 8.4 Conclusion.- 9 Binocular Interactions in Cat Visual Cortical Cells and Coding of Parameters Involved in Static and Dynamic Depth Perception.- 9.1 The Binocularity of Cortical Cells and the Ocular Dominance Scheme.- 9.2 Position Disparity Tuning Curves and the Coding of Static Depth.- 9.3 Orientation Disparity, Another Mechanism for Static Depth Discrimination?.- 9.4 Neuronal Mechanisms Underlying Dynamic Depth Perception (Motion in Depth).- 9.5 Conclusion.- 10 The Output of the Cat Visual Cortex.- 10.1 The Projections of Layer V to the Superior Colliculus, Pons, Pretectum, and Pulvinar-LP Complex.- 10.2 The Projections of Layer VI to the dLGN and the Claustrum.- 10.3 The Commissural Projections.- 10.4 The Associative Corticocortical Projections.- 10.5 Conclusion.- 11 Correlation Between Geniculate Afferents and Visual Cortical Response Properties in the Cat.- 11.1 Electrical Stimulation of the Visual Pathways.- 11.2 The Question of ON or OFF Cell Input to Cortical S Cells.- 11.3 Other Attempts to Identify the LGN Input to Cortical Cells.- 11.4 Conclusion.- 12 Intracortical Mechanisms Underlying Properties of Cat Visual Cortical Cells.- 12.1 The Role of Intracortical Inhibition.- 12.1.1 Orientation Selectivity.- 12.1.2 Direction Selectivity.- 12.1.3 End-Stopping.- 12.1.4 Ocular Dominance.- 12.1.5 Velocity Upper Cut-Off.- 12.1.6 Absence of Response to Two-Dimensional Noise.- 12.2 Properties of the Intracortical Inhibitions.- 12.3 The Structural Counterpart of Inhibitions.- 12.4 Conclusion.- 13 Non-Visual Influences on Cat Visual Cortex.- 13.1 Non-Visual Sensory Inputs to the Visual Cortex.- 13.2 Influence of Eye Movements on Visual Cortical Cells.- 13.3 The Influence of Sleep and Anesthesia.- 14 Response Properties of Monkey Striate Neurons.- 14.1 Retinotopic Organization of Area 17.- 14.2 The Input-Output Relations of Monkey Striate Cortex.- 14.3 Receptive Field Organization and Size.- 14.4 Color Specificity in Monkey Striate Cortex.- 14.5 Influence of Light Intensity and Contrast on Monkey Striate Neurons.- 14.6 Influence of Spatial Parameters.- 14.7 Influence of Spatio-Temporal Parameters.- 14.8 Ocular Dominance Distribution and Depth Sensitivity.- 14.9 Columnar Organization and Functional Architecture of Striate Cortex.- 14.10 Correlation Between Response Properties and Afferent Input.- 14.11 Conclusion.- 15 Conclusion: Signification of Visual Cortical Function in Perception.- 15.1 Operating Principles in Cat Visual Cortex.- 15.1.1 Retinotopic Organization.- 15.1.2 Filtering.- 15.1.3 "Columnar" Organization.- 15.1.4 Distributed Processing in the Primary Complex.- 15.1.5 Changes with Eccentricity.- 15.1.6 Parallel Streams Within each Area.- 15.2 The Cat and Monkey Visual Cortex as a Model: The Question of the Relationship Between Animal Physiology and Human Visual Perception.- 15.3 The Role of the Primary Visual Cortex in Visual Perception: The Significance of Parameter Specificities for Object Recognition.- References.

Visual responses in the postarcuate cortex (area 6) of the monkey that are independent of eye position.

Abstract: The visual responses of postarcuate neurons have been studied in alert behaving monkeys (Macaca nemestrina). In particular, the effect of eye position on the location of visual responses in respect to the body has been examined. It was found that a large percentage of bimodal (visual and somatosensory) neurons have visual receptive fields that are independent of eye position. The location of the visual receptive field does not change when the eyes move, but remains in register with the tactile receptive field (soma-related visually responsive neurons).

Interactions between cat striate cortex neurons.

Abstract: A series of simultaneous recordings from several striate cortex neurons were made in paralyzed, anesthetized cats. Recordings were obtained with one or two bundles of extra fine wires and originated from one and two cortical orientation columns. Standard PST histograms and, in some cases, response planes were used to analyse the neuronal receptive fields. Functional connectivity between neurons was assessed by cross-correlation of their spike trains. It was found that 61% of neuronal, pairs found within a column shared the same input, either excitatory or inhibitory. Even if neurons in a pair belonged to two different columns separated by 1 mm lateral distance, 40% of pairs still exhibited shared input coordination. This type of coordination could also encompass all combinations of simple and complex fields in the pair. Direct connections between neurons were found almost exclusively within columns: excitatory connections were found in 20% of cases and inhibitory in 8%. Direct connections were often accompanied by the other types of interactions. Only one example of excitatory and one of inhibitory direct connections were found between columns. In both cases preferred orientations were almost identical.

Topographic studies on visual neurons in the dorsolateral prefrontal cortex of the monkey.

Abstract: The topographic distribution and organization of visual neurons in the prefrontal cortex was examined in alert monkeys. The animal was trained to fixate straight ahead onto a tinty, dim light spot. While he was fixating, we presented a stationary second light spot (RF spot) at various locations in the visual field and examined unit responses of the prefrontal neurons to the RF-spot stimulus. Many prefrontal neurons, especially those located in the relatively superficial layers of the cortex, responded with a phasic and/or tonic activation to the RF spot illuminating a limited extent of the visual field, a receptive field (RF) being so determined. The visual neurons were found to be widely distributed in the prearcuate and inferior dorsolateral areas. One hemisphere mainly represented the contralateral visual field. According to the location of the neurons in these areas, their visual properties varied with respect to RF eccentricity from the fovea and in size. The neurons located in the lateral part of the areas and close to the inferior arcuate sulcus had relatively small RFs representing the foveal and parafoveal regions. When the recording site was moved medially, the RFs became eccentric from the fovea and were larger. Then, the neurons located between the caudal end of the principal sulcus and the arcuate sulcus had RFs with a considerable eccentricity. The size of the RF became progressively larger for anteriorly located neurons and this occurred generally without a change in RF eccentricity. The visual neurons were not organized on a regular pattern in the cortex with regard to their RF direction (vector angle) from the foveal region. From these observations, we conclude, first, that the prearcuate and inferior dorsolateral areas of the prefrontal cortex are functionally differentiated so that the lateral area's function is related to central vision, while that of the medial area to ambient vision. Second, the RF representation on the cortex with loss of the vector relation may generate an interaction between separate objects in visual space and may subserve the control of attention performance.

Nongeniculate afferents to striate cortex in macaques.

Abstract: Horseradish peroxidase (HRP) was injected in relatively massive amounts to cover most, or portions, of opercular striate cortex in four macaques. Absence of transcallosal or circumventricular labelling, plus discrete and consistent retrograde labelling in other areas in the four cases, assured the validity and specificity of the observations. Numerous labelled cells in regions directly bordering striate cortex, however, were excluded from the analysis because of the possibility of uptake consequent to physical diffusion. With this exception, all labelled cells were counted at roughly 2-mm intervals for one case with extensive unilateral injection of HRP. Even excluding the closely circumstriate population, the totals indicate that more than 30% of the afferent input to striate cortex arises from nongeniculate sources. Four areas of neocortex together make up about one-fourth of the total afferents: superior temporal sulcus 17.1%; inferior occipital area, 6.1%; intraparietal sulcus, 0.4%; and parahippocampal gyrus, 0.3%. Other areas projecting to striate cortex include claustrum, pulvinar, nucleus paracentralis, raphe system, locus coeruleus, and the nucleus basalis of Meynert. Cells of the latter were particularly striking with their very heavy uptake of HRP, and, even in cases of minimal effective injection, were scattered throughout an extensive area from the posterior edge of the globus pallidus passing rostrally beyond the chiasm and into the nucleus of the diagonal band. On the basis of their distribution and known cholinergic affinity, it is argued that this group also includes the cells labelled in and around lateral hypothalamus and cerebral peduncle, and that as a whole the group constitutes a cholinergic counterpart of the diffusely projecting monoaminergic systems. It seems possible that the basalis projection at first follows a fornical-subcallosal pathway to reach striate cortex via callosoperforant fibers.

Activity of cells in area 17 of the cat in absence of input from layer a of lateral geniculate nucleus.

Abstract: 1. Injections of 4 mM cobaltous chloride were used to block synaptic transmission in layer A of the lateral geniculate nucleus (LGN) without blocking fibers of passage going to or arising from other layers. 2. Selective inactivation of geniculate layer A virtually abolished all visual activity in cortical layers 4ab, 4c, and 6. Under these conditions, the stimulus-evoked response, orientation selectivity, and direction selectivity of cells in layers 2 and 3 were not seriously affected. In layer 5, the effects of the block were more variable, with special complex cells least affected and simple cells most affected. 3. Since the organization of complex receptive fields and the maintenance of normal orientation selectivity in supragranular layers survive disruption of major interlaminar interactions, it appears that much of the functional architecture of cat striate cortex does not depend on the integrity of the column. 4. These results support the idea that each layer of the LGN is a functional unit with a unique pattern of access to the various layers of visual cortex.

Relationship between preferred orientation and receptive field position of neurons in cat striate cortex.

Abstract: It has been known for two decades that neurons in mammalian visual cortex respond selectively to stimuli falling on the retina at a particular angular orientation (Hubel and Wiesel, '62). Recent evidence suggests that most cat retinal ganglion cells (Levick and Thibos, '82) and relay cells (Vidyasagar and Urbas, '82) in the cat's dorsal lateral geniculate nucleus are also orientation selective. In the retina there is a systematic relationship between receptive field position (polar angle) and preferred orientation. Outside of the area centralis, most retinal ganglion cells have oriented dendritic fields (Leventhal and Schall, '83) and respond best to stimuli oriented radially, i.e., oriented parallel to the line connecting their receptive fields to the area centralis (Levick and Thibos, '82). This relationship is strongest close to the horizontal meridian (the visual streak) of the retina (Leventhal and Schall, '83). To determine if a relationship between preferred orientation and polar angle exists in visual cortex, the preferred orientations and receptive field positions of 768 striate cortical neurons were studied. As in the retina, a systematic relationship exists between preferred orientation and visual field position in area 17. In parts of striate cortex 15–80° from the area centralis projection there is a strong tendency for cells to respond best to lines oriented radially. In regions 4–15° from the area centralis projection this relationship appears weaker. In regions subserving the central 4° of visual angle no such relationship exists. Throughout area 17 the relationship between preferred orientation and polar angle is strongest in regions subserving the horizontal meridian. It is suggested that the systematic relationship between preferred orientation and polar angle which begins in the retina provides an intrinsic framework for the organized arrangement of orientation “columns” in visual cortex (Hubel and Wiesel, '63). This relationship may also be responsible for the “oblique effect” as well as the visual system's preferential response to radially oriented gratings (Rovamo et al.,'82).

Large layer VI neurons of monkey striate cortex (Meynert cells) project to the superior colliculus.

Abstract: After injections of the enzyme horseradish peroxidase (HRP) into the superior colliculus of macaque monkeys, labelled cells in the neocortex were found to be restricted to layer V in all areas except striate visual cortex. In striate visual cortex, cortico-tectal cells were found both in layer V and in layer VI. The labelled cells in the two layers belonged to morphologically different populations: those of layer V were the common pyramidal cells and those of layer VI were identified as solitary cells of Meynert. This finding may provide new insights into the physiology of the cortico-collicular pathways. It also shows that the striate area in primates differs, with respect to cortico-tectal laminar specificity, from other neocortex.

Development of orientation columns in cat striate cortex revealed by 2-deoxyglucose autoradiography.

Abstract: In the striate cortex of adult monkeys and cats, both electrophysiology1-3 and the 2-deoxyglucose autoradiographic technique of Sokoloff4-8 suggest that neurones are arranged in functional columns or slabs that run through the full thickness of the cortex, each column containing cells with a preference for a particular orientation of line or edge in the visual field. There is disagreement, however, concerning the organization of visual cortex in very young animals and the role of visual experience in cortical development. Orientation-selective neurones clearly exist in immature cat cortex, but reports differ on their frequency, angular selectivity and degree of columnar organization (see ref. 9 for review). We have used 2-deoxyglucose autoradiography to investigate the development of cat striate cortex. This technique reveals the spatial distribution of activity in populations of neurones and should therefore provide information about how the columnar pattern develops and whether its maturation depends on visual stimulation. We report here that in normal animals, periodic metabolic labelling around layer IV was first clearly observed at 21 days of age and by 35 days the pattern had become truly columnar; in a matched series of animals deprived of normal pattern vision no differential label was observed except for weak periodicity in a single 35-day-old animal. These results suggest that cat striate cortex is immature at the time of eye-opening and that visual experience is crucial for normal maturation.

Functional role of association fibres for a visual association area: the posterior suprasylvian sulcus of the cat.

Abstract: This paper reports on experiments in which the effect of disconnexion of association fibres from Area 17/18 to the posterior suprasylvian cortex (PSSC) was investigated. In the control experiments, all neurons had large receptive fields in the central 5–10 ° of the visual field without detailled retinotopy. In the medial bank of PSSC, receptive fields were located in the contralateral visual field, while receptive fields of neurons in the lateral bank were located ipsilaterally. Neurons in PSSC could be excited by electrical stimulation of the ipsilateral Area 17/18 boundary, of the medial pulvinar (N. lat. post., pars, lat.) and the lateral geniculate body. About 2/3 of all neurons could be excited from all these regions, although with varying latencies. After acute and chronic subpial undercutting of the representation of the central 5–10 ° of the ipsilateral area 17/18, visual response properties including direction sensitivity, receptive field size and ocularity of PSSC-neurons in the medio-posterior bank did not change significantly. After ablation of the whole contralateral visual cortex (including PSSC and a wide region of the contralateral Clare-Bishop area) the input from the ipsilateral eye was considerably diminished, but other response properties did not change significantly. These essentially negative findings are discussed in relation to different findings of other authors, and it is argued that the subpial undercutting of only the central visual field representation may have prevented damage to the ipsilateral suprasylvian cortex and its afferents, which is difficult to avoid if the whole area 17 is ablated by suction. It is proposed, that association fibres may only “unspecifically” excite neurons in related association areas rather than impose onto them specific response features. These latter are derived, also in association areas, essentially from their thalamic afferents and their intracortical interaction.

Orientation shift between upper and lower layers in monkey visual cortex.

Abstract: Microelectrode penetrations nearly normal to the layers of foveal striate cortex in awake, behaving monkeys reveal a shift in orientation preference between cells in the upper and lower layers. Mean shift size for 57 penetrations is 54.8 degrees, with 70% of the penetrations showing shifts of 45-90 degrees. Marking lesions localize the shift to the border between layers 4C and 5. The data are suggestive of inhibition between the upper and lower layers within an "orientation column".

Orientation selectivity and the spatial distribution of enhancement and suppression in receptive fields of cat striate cortex cells.

Abstract: The relationship between orientation selectivity and spatial receptive field organization was analyzed Receptive field maps were made with a dual stimulus technique where an optimally oriented activation slit was presented in the most responsive region to produce activity against which the effect of a test spot in various positions was determined Both simple and complex cells had receptive fields which were subdivided into adjacent elongated and antagonistic subrogions When the two stimuli were presented in phase (both ON or OFF simultaneously) the fields had a central enhancement region with a strong suppression flank on one or both sides Optimal slit orientation was related to the location of the suppression flank relative to the location of the central enhancement region, and the degree of orientation selectivity to the shape of the subregions and the distance between them Estimated orientation tuning curves calculated from the receptive field maps gave satisfactory first approximations to experimental curves

Different geniculate inputs to B and C cells of cat striate cortex.

Abstract: Cells with uniform receptive fields were selected for extra cellular recording in the striate cortex of anaesthetised cats. From their responses to electrical stimulation at three sites in the primary visual pathway the cells were grouped according to their ordinal position and whether their afferent drive came from the brisk sustained or brisk transient type of LGN neuron. From differences in laminar distribution and afferent stream the population was divided into 4 subgroups. Within these 4 subgroups there were two basic visual response patterns, which had been identified previously, and attributed to B and C cells. The B cells, which have a smaller receptive field, a lower spontaneous activity and cut-off velocity than C cells, were found to receive their input from slowly conducting afferents while the afferents to C cells arose from the fast stream. A high proportion of both B and C cells received a monosynaptic or direct drive from the optic radiations and responded with multiple spiking to a single electrical shock. Multiple spiking was viewed as evidence of secondary pathways travelling via intermediate cortical neurons to contribute to the cell's input. An examination of the visual properties of all subclasses showed that the more obvious differences in receptive field properties were associated with the type of afferent coming from the LGN rather than with the ordinal or the laminar position of the cell. In this respect the cells in the C/B family resemble S cells, whose receptive field properties also show a dependence on the type of LGN input.

Effects on binocular activation of cells in visual cortex of the cat following the transection of the optic tract.

Abstract: Cells in area 17 of the cortex are generally activated either directly through a retino-thalamic pathway or indirectly via a contralateral hemispherecallosal pathway The aim of the present experiment was to evaluate the effects of eliminating this second pathway on the binocular activation of cells in the primary visual cortex The optic tract was sectioned on one side in 18 cats and unit activity was recorded in the contralateral hemisphere This hemisphere should receive normal thalamo-cortical inputs but no visual callosal input These animals were compared to 21 normal cats Extracellular electrophysiological recordings were carried out in the conventional way using tungsten microelectrodes and N2O anaesthesia Results indicated that the proportion of binocular cells found in the cortex of tract sectioned animals was lower than that found in normal animals However, this decrease in binocularity could be essentially attributed to cells having receptive fields situated to within 4 ° of the vertical meridian of the visual field These results are interpreted as being congruent with the demonstrated anatomo-physiological projections of the callosal system

Double orientation tuning of visual cortex neurons in the cat

Abstract: Orientation tuning of 148 visual cortex neurons was investigated in immobilized unanaesthetized cats. The light slit of the optimal size flashing in the receptive field was used as a stimulus. It was found that 88 neurons (59%) had double orientation tuning: preferred and additional. Additional orientation was either orthogonal or at a sharp angle to the preferred orientation. In 64% neurons double orientation was found only after a change of the contrast between stimulus and background. This kind of tuning in many neurons appeared only at definite moments after the beginning of the stimulus. Model analysis showed that double orientation tuning might be a consequence of the specific structure of neuronal receptive fields. The functional meaning of double orientation tuning and its role in the detection of visual images signs are discussed.

Differences in orientation and receptive field position between supra- and infragranular cells of cat striate cortex and their possible functional implications

Abstract: On the postlateral gyrus of the cat striate cortex the cells' preferred orientation and the location of their receptive fields was measured as a function of cortical depth in penetrations as parallel as possible to the radiating fibres. In most penetrations the majority of infragranular cells showed orientation preferences 45°---90° different from the preferred orientations of supragranular cells. In addition, aggregate receptive fields from the same eye of supra- and infragranular cells were spatially shifted against each other. Using different columnar models these results are discussed in terms of spatial contrast enhancement for two parallel mechanisms in upper and lower layers, determined for pattern discrimination and movement detection.

A functional model of the wiring of the simple cells of visual cortex

Abstract: A computer model of the simple cells in the mammalian visual cortex was constructed. The model cells received inputs from a great number of isopolar centre/surround cells assumed to be located in the lateral geniculate nucleus (LGN). The distribution of input to the model simple cells was either inhibitory/ excitatory or inhibitory/excitatory/inhibitory. Such arrangements produced receptive fields containing four or five consecutively antagonistic subfields. Responses produced by the model cells to different types of stimuli (periodical as well as nonperiodical) were obtained and compared to responses of living cells reported from various laboratories under comparable stimulus conditions. In all the situations tested, the responses of the model cells corresponded qualitatively very well to those of living cells. It was seen that the same wiring mechanism was able to account for orientation selectivity, spatial frequency filtering, various phase relationships between stimulus and response, subfield orientational selectivity, and slight end-inhibition. Furthermore, the receptive fields of the model simple cells closely resemble Gabor functions.

Effects of luminance gradient reversal on complex cells in cat striate cortex.

Abstract: We have examined the responsiveness of various classes of complex cells in the cat's striate cortex to stimuli comprising bars aligned with segments of opposite luminance contrast. In all cases, a short segment of opposite polarity depressed, without abolishing, the bar response; within the length summation zone, the response to the bar in the presence of longer segments matched the length summation characteristics of each cell, depressed by a constant amount. The results could not be accounted for purely on the basis of convergent input from simple cells, whose behaviour to comparable stimuli has previously been reported (Hammond and MacKay 1981a).

Receptive field dynamics of neurons in the cat visual cortex and lateral geniculate body

Abstract: Spike responses of single neurons in the primary visual cortex and lateral geniculate body to random presentation of local photic stimuli in different parts of the receptive field of the cell were studied in acute experiments on curarized cats. Series of maps of receptive fields with time interval of 20 msec obtained by computer enabled the dynamics of the excitatory and inhibitory zones of the field to be assessed during development of on- and off-responses to flashes. Receptive fields of all cortical and lateral geniculate body neurons tested were found to undergo regular dynamic reorganization both after the beginning and after the end of action of the photic stimulus. During the latent period of the response no receptive field was found in the part of the visual field tested, but later a small zone of weak responses appeared only in the center of the field. Gradually (most commonly toward 60–100 msec after application of the stimulus) the zone of the responses widened to its limit, after which the recorded field began to shrink, ending with complete disappearance or disintegration into separate fragments. If two bursts of spikes were generated in response to stimulation, during the second burst the receptive field of the neuron changed in the same way. The effects described were clearly exhibited if the level of background illumination, the intensity of the test bars, their contrast with the background, duration, angles subtended, and orientation were varied, although the rate and degree of reorganization of the receptive field in this case changed significantly. The functional importance of the effect for coding of information about the features of a signal by visual cortical neurons is discussed.