Showing papers on "Orientation column published in 1968"

Receptive fields and functional architecture of monkey striate cortex

Abstract: 1. The striate cortex was studied in lightly anaesthetized macaque and spider monkeys by recording extracellularly from single units and stimulating the retinas with spots or patterns of light. Most cells can be categorized as simple, complex, or hypercomplex, with response properties very similar to those previously described in the cat. On the average, however, receptive fields are smaller, and there is a greater sensitivity to changes in stimulus orientation. A small proportion of the cells are colour coded. 2. Evidence is presented for at least two independent systems of columns extending vertically from surface to white matter. Columns of the first type contain cells with common receptive-field orientations. They are similar to the orientation columns described in the cat, but are probably smaller in cross-sectional area. In the second system cells are aggregated into columns according to eye preference. The ocular dominance columns are larger than the orientation columns, and the two sets of boundaries seem to be independent. 3. There is a tendency for cells to be grouped according to symmetry of responses to movement; in some regions the cells respond equally well to the two opposite directions of movement of a line, but other regions contain a mixture of cells favouring one direction and cells favouring the other. 4. A horizontal organization corresponding to the cortical layering can also be discerned. The upper layers (II and the upper two-thirds of III) contain complex and hypercomplex cells, but simple cells are virtually absent. The cells are mostly binocularly driven. Simple cells are found deep in layer III, and in IV A and IV B. In layer IV B they form a large proportion of the population, whereas complex cells are rare. In layers IV A and IV B one finds units lacking orientation specificity; it is not clear whether these are cell bodies or axons of geniculate cells. In layer IV most cells are driven by one eye only; this layer consists of a mosaic with cells of some regions responding to one eye only, those of other regions responding to the other eye. Layers V and VI contain mostly complex and hypercomplex cells, binocularly driven. 5. The cortex is seen as a system organized vertically and horizontally in entirely different ways. In the vertical system (in which cells lying along a vertical line in the cortex have common features) stimulus dimensions such as retinal position, line orientation, ocular dominance, and perhaps directionality of movement, are mapped in sets of superimposed but independent mosaics. The horizontal system segregates cells in layers by hierarchical orders, the lowest orders (simple cells monocularly driven) located in and near layer IV, the higher orders in the upper and lower layers.

Analysis of retinal correspondence by studying receptive fields of rinocular single units in cat striate cortex

Abstract: The concept of corresponding retinal points was examined in terms of the binocular receptive fields of neurons in Area 17 of the cerebral cortex of the cat. Only a proportion of the binocular receptive field pairs can be accurately superimposed at the one time in a given plane. The fields which are not corresponding are said to show receptive field disparity. The attempt has been made to establish, on a quantitative basis, the parameters of the receptive field disparities that occur within 5° of the visual axis. A new method was used for defining the zero (vertical) meridian. Very effective paralysis of the extraocular muscles was achieved and the very small residual eye movements that occurred were regularly monitored so that corrections could be applied to the plotted positions of the receptive field pairs. The distribution of the receptive field disparities about the position of maximal correspondence has a range of about ±1.2° (S.D. 0.6°) in both the horizontal and vertical directions for fields in the vicinity of the visual axis. Panum's fusional area may represent the extent to which receptive fields in the one eye, all with the same visual direction, are linked to fellow members of a pair in the other eye over a range of receptive field disparities. A naso-temporal overlap of receptive fields occurs which is probably little if any more than can be accounted for on the basis of the disparity of receptive fields lying along the zero (vertical) meridian. When the extraocular muscles are paralyzed the eyes diverge and the binocular receptive field pairs are separated on the tangent screen. The distribution of the horizontal and vertical separations of the receptive field pairs have been examined.

Interrelationships of striate and extrastriate cortex with the primary relay sites of the visual pathway.

Abstract: Several recent studies have indicated that the optic tectum or superior colliculus may serve more important and diverse functions than was formerly considered (Denny-Brown, 1962; Sprague and Meikle, 1965) and there is also evidence that the cortical connexions of the colliculus are significant in such functions (Sprague, 1966a, b). It has been established for some time that the superior colliculus receives a substantial projection from the neocortex (Meikle and Sprague, 1964), but relatively little attention has been paid to the organization that may be present in this system. The finding in the avian brain of a precise relationship between the representation of the retina upon the optic tectum and the origin of one group of tectal efferents (McGill, Powell, and Cowan, 1966), taken together with the well-ordered representation of the retina upon both the superior colliculus (Apter, 1945) and the visual cortex in the cat (Talbot and Marshall, 1941; Bilge, Seneviratne, and Whitteridge, 1963; Hubel and Wiesel, 1965) raises the question whether a comparably close relationship might not be present in the termination of the two distinct groups of afferents to the superior colliculus from the visual pathway-from the retina and from the visual cortex. As the architectonic subdivisions of the visual cortex (Otsuka and Hassler, 1962) have been shown to be functionally different (Hubel and Wiesel, 1965), and because there are separate representations of the retina in these areas, there is also the possibility that each of these areas projects independently upon the colliculus. A further aspect of the projection of the neocortex upon the tectum that should be considered is the relationship of the origin of those cortico-tectal fibres from 'nonvisual' parts of the cortex to such functional areas as the auditory and somatic sensory areas and the motor cortex, and also the relationship of the termination of these fibres to that of the afferent fibres to the superior colliculus from ascending sensory pathways. The present investigation has been mainly concerned with these problems of the projection of the neocortex upon the superior colliculus in the cat (Garey, 1965), but as our material has also provided evidence on the cortical and other subcortical connexions of the visual area, certain of these findings have been included here because of their close interrelationship. The experimental results are presented and discussed in three sections, and the possible significance of these and other recent findings in the thalamocortical and mesencephalic connexions of the visual system will be finally considered in relation to the function of the superior colliculus. In the meantime Lund (1964, 1966) has published a study of the occipito-tectal pathway in the rat in which he found that 'areas of cortex project to areas of colliculus receiving fibres from the same areas of retina', and Kuypers and Lawrence (1967) have described the organization in the projection of the cerebral cortex upon the brain-stem in the monkey.

Binocularly driven neurons in visual cortex of split-chiasm cats.

Abstract: In cats with midsagittal section of the optic chiasm, some visual cortex neurons can be driven not only by the ipsilateral eye, through the direct geniculocortical pathways, but also by the contralateral eye, through the opposite visual cortex and corpus callosum. The receptive fields and the response characteristics observed upon stimulation of the contralateral eye are very similar to those observed upon stimulation of the ipsilateral eye; the two monocular receptive fields of a given cell lie in corresponding points of heteronymous halves of the visual field in close contact with the vertical meridian, thus adding in visual space and forming a binocular receptive area which crosses the vertical meridian and extends equally on either side of it.

Visual Cortex Neurons: Response to Stimuli during Rapid Eye Movements

Abstract: While awake, unanesthetized monkeys held their eyes stationary, a motionless or slowly moving stimulus falling on the receptive field of striate cortex neurons produced an excitatory response. When a rapid eye movement was made across the same stimulus, many of these neurons continued to give an excitatory response. But the discharge of other neurons was unchanged or was suppressed during the eye movement.

Response Characteristics of Single Neurons in the Rabbit Visual Cortex

Abstract: Unitary discharges were extracellularly recorded from cortical cells in the rabbit's visual area. Most of the cortical units were responsive to large-field illumination which was turned on and off at about 0.8/sec. Response characteristics of cortical cells were largely similar to those of retinal ganglion cells. One hundred and twenty-nine units which were analyzed successfully were categorized into four classes according to the features of their receptive fields: simple, asymmetric, complex and compound. Especially, compound receptive fields were so named on the basis of the finding that the whole receptive field consisted of three separable complex fields. A columnar arrangement of cortical neurons was suggested on the basis of the fact that the localization of the receptive fields of units involved in a particular column was almost identical in the visual field. No other common properties to specialize the column was detected. Most of the receptive fields of units which were localized in the visual streak were oval in shape with their long axis horizontal as described in retinal ganglion cells. It is likely that in the rabbit's visual cortex no more elaborate analysis is made on in-coming visual information, but rather some integrative action is carried out for further processing.