Showing papers on "Orientation column published in 1976"

Quantitative studies of single-cell properties in monkey striate cortex. II. Orientation specificity and ocular dominance

Abstract: 1. Quantitative analyses of orientation specificity and ocular dominance were carried out in striate cortex of the rhesus monkey. 2. Sharpness of orientation selectivity was greater for simple (S type) than for complex (CX type) cells. CX-type cells became more broadly tuned in the deeper cortical layers: S-type cells were equally well tuned throughout the cortex. 3. Sharpness of orientation selectivity for S-type cells was similar at all retinal eccentricities studied (0 degrees - 20 degrees from the fovea):in CX-type cells orientation selectivity decreased slightly with increasing eccentricity. 4. The orientation tuning of binocular cells was similar when mapped separately through each eye. 5. Orientation selectivity and direction selectivity are independent of each other, suggesting that separate neural mechanisms give rise to them. 6. More CX-type cells can be binocularly activated than S-type cells (88% versus 49%). The ocular dominance of S-type cells is similar in all cortical layers: for CX-type cells there is an increase in the number of cells in ocular-dominance category 4 in layers 5 and 6.

Enhancement of visual responses in monkey striate cortex and frontal eye fields.

Abstract: 1. We have studied the visual enhancement effect in two areas of the cerebral cortex of monkeys. The response of the cells to a visual stimulus was determined both when the monkey used the visual stimulus as the target for a saccadic eye movement and when he did not. 2. In striate cortex cells with nonoriented, simple, complex, and hypercomplex receptive-field types were studied. Clear enhancement of the response to the appropriate visual stimulus was seldom seen when the monkey used the stimulus as a target for a saccade. In addition, any enhancement effect seen was nonselective; it occurred whether the monkey made a saccade to the receptive-field stimulus or some other stimulus at a point distant from the receptive field. The enhancement also occurred whether the monkey made a saccade to the stimulus or just released the bar when the stimulus dimmed. 3. This nonselective enhancement in striate cortex is in striking contrast to the selective enhancement of the visual response seen in the superior colliculus. The different characteristics of the enhancement in striate cortex and the observation of enhancement in the colliculus following ablation of striate cortex suggest that this cortical area is an unlikely source of the collicular enhancement. 4. These observations reinforce the distinction between striate cortex and superior colliculus. Striate cortex is an excellent analyzer of stimulus characteristics but a poor evaluator of stimulus significance. The superior colliculus is an excellent evaluator but a poor analyzer. 5. The area of frontal eye fields in which cells have clear visual responses has been better localized. Enhancement of the visual response of these cells also occurs and, at least for some cells, the response enhancement is selective. The response enhancement, like the visual properties of these frontal eye field cells, appears to be more closely related to the properties of superior colliculus cells than to striate cortex cells.

Metabolic mapping of the primary visual system of the monkey by means of the autoradiographic [14C]deoxyglucose technique

Abstract: An autoradiographic technique that employs 2-[14-C]deoxyglucose to measure the local rates of glucose utilization within the brain has been applied to the binocular visual system of the Macaque monkey. This method, which pictorially displays the relative rates of glucose consumption in the component structures of the brain, delineates the regions of altered functional activity because of the close relationship between functional activity and energy metabolism. Bilateral retinal stimulation results in the delineation of different rates of glucose consumption in at least four cytoarchitectural layers of the striate cortex. The most intense metabolic activity appears to be in Layer IV, the locus of the termination of the geniculocortical pathway. Bilateral visual occlusion lowers the rates of glucoes consumption in striate cortex and markedly reduces the metabolic differentiation of the various layers. Unilateral visual deprivation delineates the laminae of the lateral geniculate body and the ocular dominance columns of the striate cortex. It also results in the autoradiographic visualization of regions with normally monocular input in the striate cortex, such as the rostral portions of the mushroom-like configurations in the calcarine cortex, which represent the extreme temporal crescents of the visual fields, and small regions in the most caudal part of the mushroom configurations, which are believed to represent the cortical loci of the blind spotsof the visual fields.

Functional organization in the visual cortex of the golden hamster

Abstract: The visual cortex of the golden hamster was studied by means of multi-unit and single unit recording, which revealed three separate retinotopic maps of the visual field in the posterior cortex. V1, corresponding to cyto-architectonic area 17, has the contralateral temporal field represented medially, the central visual field (extending about 10 deg ipsilateral) represented laterally and the lower field anteriorly. The borders of the map, especially for the upper field, seem to be more restricted than the whole visual field available to the contralateral hemiretina: V1 probably does not represent the extreme periphery of the field. A large fraction of V1 has binocular input, for up to about 50 deg lateral to the vertical midline. There is a retinotopic reversal near the representation of the vertical midline where V1 meets V2 (corresponding to the more lateral "area 18a"). There is another retinotopic reversal at the extremity of the contralateral field representation, where V1 meets Vm (the medial visual area, corresponding to "area 18"). V2 and Vm each contain a reduced mirror image version of the map in V1. Almost all isolated single units in V1 have receptive fields that can be classified as radially symmetrical (60%) or asymmetrical (35%). Symmetrical fields have ON (13%), OFF (4%), ON-OFF (30%) or "SILENT" (12%) central areas when plotted with flashing spots. There are minor but not striking differences between these groups in their field sizes, velocity preferences and so on. They almost invariably prefer moving to stationary stimuli but are not selective for orientation or direction of movement. Asymmetrical fields are of four types, three of which (type 1, 11%; type 2, 17%; and type 3, 2%) are orientation selective and resemble simple, complex and hypercomplex cells in the cat cortex. Some of these have direction as well as orientation preference. Axial movement detectors (5%) have a selectivity for one axis of motion, and thus prefer one orientation of edge, but respond equally well to movement of a spot. Vertical and horizontal orientation preferences, especially the latter, are much the most common. There is some evidence of clustering of cells according to receptive field type and, possibly, preferred orientation. Asymmetrical cells are, relatively somewhat rarer in the deeper cortical layers. Within the binocular segment, fully 89% of cells are binocularly driven and the receptive fields are similar in the two eyes. Receptive fields tend to increase in size away from the area centralis representation and, in a complementary fashion, the magnification factor decreases from up to 0.1 mm/deg at the area centralis representation to about 0.02 mm/deg for the peripheral field.

Reversal of the physiological effects of monocular deprivation in the kitten's visual cortex.

Abstract: 1. Twenty-three kittens were monocularly deprived of vision until the age of 4, 5, 6 or 7 weeks. Their deprived eyes were then opened, and their experienced eyes shut for a further 3-63 days. After this time physiological recordings were made in the visual cortex, area 17. Three control kittens, monocularly deprived for various periods, showed that at the time of reverse-suturing, few neurones could be influenced at all from the deprived eye. 2. Following reverse-suturing, the initially deprived eye regained control of cortical neurones. This switch of cortical ocular dominance was most rapid following reverse-suturing at the age of 4 weeks. Delaying the age of reverse-suturing reduced the rate and then the extent of the cortical ocular dominance changes. 3. The cortex of reverse-sutured kittens is divided into regions of cells dominated by one eye or the other. The relative sizes of these ocular dominance columns changed during reversed deprivation. The columns devoted to the initially deprived eye were very small in animals reverse-sutured for brief periods, but in animals that underwent longer periods of reversed deprivation, the columns driven by that eye were larger, while those devoted to the initially open eye were smaller. 4. Clear progressions of orientation columns across the cortex were apparent in many of the kittens, but, in contrast to the situation in normal or strabismic kittens, these sequences were disrupted at the borders of eye dominance columns: the cortical representations of orientation and ocular dominance were not independent. 5. Binocular units in these kittens were rather rare, but those that could be found often had dissimilar receptive field properties in the two eyes. Commonly, a cell would have a normal orientation selective receptive field in one eye, and an immature, unselective receptive field in the other. Cells that had orientation selective receptive fields in both eyes often had greatly differing orientation preferences in the two eyes, occasionally by nearly 90 degrees. 6. During the reversal of deprivation effects, the proportion of receptive fields exhibiting mature properties declined in the initially experienced eye, while the proportion increased in the initially deprived eye. Similarly, the average band width of orientation tuning of receptive fields in the initially deprived eye decreased, while that of receptive fields in the initially experienced eye increased. 7. One kitten was reverse-sutured twice, to demonstrate that cortical ocular dominance may be reversed a second time, even after one reversal of ocular dominance. 8. It is suggested that the sensitive period for cortical binocular development consists of two phases. In the first phase, all cortical neurones may be modified by experience, but the rate at which they may be modified decreases with age. In the second phase, an increasing number of cortical neurones becomes fixed in their properties, while those that remain modifiable are as modifiable as they were at the end of the first phase. 9...

Lateral geniculate relay of slowly conducting retinal afferents to cat visual cortex.

Abstract: 1. Lateral geniculate neurones of the cat were studied in terms of the latency for activation by local electrical stimulation of the retina, the latency of electrical activation from the visual cortex and properties of receptive fields. Most of the units were relay cells (antidromic activation from visual cortex) but a small proportion were trans-synaptically activated from the cortex. The latter group included units with on-off, on-centre or off-centra receptive fields. 2. Direct activation of lateral geniculate neurones from local electrical stimulation of retinal ganglion cells or their axons in the retina was identified by the sharpness of timing of the elicited impulses. This procedure revealed the existence of slowly conducting axons relaying in the lateral geniculate nucleus. 3. The distribution of latencies for direct activation from the retina was bimodal with an extended tail of long values. It is similar to the distribution of antidromic latencies of retinal ganglion cells following stimulation of the optic tract. 4. There was a tendency for geniculate neurones with fast input from the retina to have fast axons to the visual cortex and correspondingly for medium-speed and slow input. 5. The previous classification of geniculate receptive fields into sustained and transient types was extended to include commonly encountered 'brisk' and uncommonly encountered 'sluggish' varieties of each. The extension was based on visual properties and latency for direct electrical activation from the retina. Units with receptive fields differing from the familiar on-centre or off-centre concentric pattern were encountered rarely; they included colour-coded fields, local-edge-detectors and one edge-inhibitory off-centre type.

Receptive-field characteristics of neurons in cat striate cortex: Changes with visual field eccentricity

Abstract: 1. Receptive-field properties of 214 neurons from cat striate cortex were studied with particular emphasis on: a) classification, b) field size, c) orientation selectivity, d) direction selectivity...

Representation of the visual field on the medical wall of occipital-parietal cortex in the owl monkey

Abstract: The medical visual area is located on the medical wall of occipital-parietal cortex. A much larger proportion of this area is devoted to the representation of the more peripheral parts of the visual field than in any other cortical area or subcortical visual structure than has been mapped previously in any species of primate.

Bilateral cortico-tectal projection from the visual cortex in the cat

Abstract: THERE is anatomical and electrophysiological evidence for a heavy and well organised fibre projection from the visual cortex on the superior colliculus of the midbrain in several species1–4. In the cat, areas 17, 18 and 19 of the visual cortex each project to the colliculus and the arrangement is such that a point in the cortex related to a particular part of the retina sends fibres to that part of the colliculus receiving fibres directly from the same part of the retina. The available evidence is for a cortico-tectal projection to the ipsi-lateral superior colliculus only. In several brains of cats with lesions involving the visual cortex of one hemisphere, fibre degeneration has now also been found in the superior colliculus of the opposite side. This observation provides an explanation for several findings made in electrophysiological studies of the representation of the visual field in the superior colliculus which have been difficult to interpret, and it should help in the interpretation of functional studies on the visual connections of the cerebral hemisphere.

Unusually large receptive fields in cats with restricted visual experience.

Abstract: The receptive fields of striate cortex neurons were analyzed in cats which had restricted or no visual experience. Two groups of animals were investigated: 1. cats which were deprived from contour vision over variable periods of time up to 1 year and 2. kittens whose visual experience was restricted to vertically oriented gratings of constant spatial frequency which moved unidirectionally at a fixed distance in front of the restrained animals. In both preparations exceedingly large receptive fields (up to 20° in diameter) were encountered, especially in cells located in supragranular layers. These large receptive fields never extended over more than 2° into the ipsilateral hemifield. Their sensitivity profile was frequently asymmetric and contained discontinuities. Many of these large receptive fields consisted of several excitatory subregions which were separated from each other by as much as 15°. Often but not always the most sensitive area was located where the retinotopic map predicted the receptive field center. The orientation and direction selectivity and also the angular separation of such multiple excitatory bands often matched precisely the orientation, direction and spatial frequency of the experienced moving grating. In other fields with multiple excitatory subregions such a correspondence could not be established; the various subregions could even have different orientation and direction selectivities. From these unconventional receptive fields it is concluded that the function of cat striate cortex is not confined to a point by point analysis of the visual field in retinotopically organized and functionally isolated columns.

Responses of cells in the dorsal lateral geniculate complex of the cat to textured visual stimuli.

Abstract: Light and dark edges and bars have b e e n used extensively in s ingle-uni t studies at var ious levels of the cat 's visual system. However , in recent reports f rom this labora tory , H a m m o n d and MacKay (1975a, b, 1976) have demons t r a t ed that s imple and complex cells in the cat 's striate cortex are differential ly sensit ive to mo t ion of tex tured 'visual noise ' . This repor t describes the responses of sus ta ined and t rans ien t cells recorded f rom the l amina t ed la teral genicula te ( L G N d ) and media l i n t e r l amina r (MIN) nucle i of the lateral genicula te complex to tex tured 'no ise ' st imuli (see lower inset, Fig. 1).

Spatial resolution and nonlinearities of simple cells in the cat visual cortex measured with parallel line pairs

Abstract: The spatial resolution of simple cells in cat visual cortex was measured by stimulation with pairs of 6? wide parallel light bars of various spacings. These double lines were moved across the receptive field and were taken as resolved if there was a 10% deflection between the double peak responses of cells. As a control, recordings were also made from several geniculate fibers. The smallest bar separations resolved by simple cells were larger than those which have been found for cells of the lateral geniculate nucleus (LGN), although the smallest cortical receptive field centers were as small as those of LGN-cells. The correlation between optimal resolving power of a cell and the width of its excitatory receptive field was much weaker in cortical simple cells than in LGN cells. In contrast to the LGN, the double line responses of most simple cells differ markedly from an additive superposition of two single line responses spaced according to the actual interline distance. As possible mechanisms underlying these nonlinearities three different connectivity schemes were investigated. Two of these models were based on receptive field concepts; the third one used intracortical circuits. Only the latter model could explain all the nonlinear effects seen in the neurophysiological experiments.

Layer-by-layer analysis of visual cortical evoked potentials during prenatal development of the cat

Abstract: 1. Layer-by-layer analysis of potentials arising in the striate cortex in response to electrical stimulation of the optic nerve was carried out on cat fetuses and kittens during the first days after birth. 2. Layer-by-layer analysis of the distribution of potentials and the discovery of the location of their “source” and “sink” showed that during the last 3 weeks of intrauterine life and in early postnatal ontogeny the application of a single stimulus to the optic nerve causes the appearance of two negative potentials in the cortex, located in different layers. 3. After the arrival of a volley of afferent impulses in the cortex the first high-amplitude negative potential arises in the middle layers of the cortex. It is evidently a combined EPSP of a population of pyramidal and stellate neurons lying in the middle layers of the cortex. 4. The second focus of excitation arises 40–50 msec after the first. Layer-by-layer analysis shows that it is due to excitation of neurons located in the upper layers of the cortex, most probably in the apical dendrites of pyramidal neurons. 5. The results of this layer-by-layer analysis of EP of the primary visual projection cortex show that the characteristic temporal and spatial sequence of activation of neurons found in the visual cortex of adult animals is formed during the second half of the intrauterine period of development.