Showing papers on "Orientation column published in 1977"

Ferrier Lecture: Functional Architecture of Macaque Monkey Visual Cortex

Abstract: Of the many possible functions of the macaque monkey primary visual cortex (striate cortex, area 17) two are now fairly well understood. First, the incoming information from the lateral geniculate bodies is rearranged so that most cells in the striate cortex respond to specifically oriented line segments, and, second, information originating from the two eyes converges upon single cells. The rearrangement and convergence do not take place immediately, however: in layer IVc, where the bulk of the afferents terminate, virtually all cells have fields with circular symmetry and are strictly monocular, driven from the left eye or from the right, but not both; at subsequent stages, in layers above and below IVc, most cells show orientation specificity, and about half are binocular. In a binocular cell the receptive fields in the two eyes are on corresponding regions in the two retinas and are identical in structure, but one eye is usually more effective than the other in influencing the cell; all shades of ocular dominance are seen. These two functions are strongly reflected in the architecture of the cortex, in that cells with common physiological properties are grouped together in vertically organized systems of columns. In an ocular dominance column all cells respond preferentially to the same eye. By four independent anatomical methods it has been shown that these columns have the from of vertically disposed alternating left-eye and right-eye slabs, which in horizontal section form alternating stripes about 400 $\mu $m thick, with occasional bifurcations and blind endings. Cells of like orientation specificity are known from physiological recordings to be similarly grouped in much narrower vertical sheeet-like aggregations, stacked in orderly sequences so that on traversing the cortex tangentially one normally encounters a succession of small shifts in orientation, clockwise or counterclockwise; a 1 mm traverse is usually accompanied by one or several full rotations through 180 degrees, broken at times by reversals in direction of rotation and occasionally by large abrupt shifts. A full complement of columns, of either type, left-plus-right eye or a complete 180 degrees sequence, is termed a hypercolumn. Columns (and hence hypercolumns) have roughly the same width throughout the binocular part of the cortex. The two independent systems of hypercolumns are engrafted upon the well known topographic representation of the visual field. The receptive fields mapped in a vertical penetration through cortex show a scatter in position roughly equal to the average size of the fields themselves, and the area thus covered, the aggregate receptive field, increases with distance from the fovea. A parallel increase is seen in reciprocal magnification (the number of degrees of visual field corresponding to 1 mm of cortex). Over most or all of the striate cortex a movement of 1-2 mm, traversing several hypercolumns, is accompanied by a movement through the visual field about equal in size to the local aggregate receptive field. Thus any 1-2 mm block of cortex contains roughly the machinery needed to subserve an aggregate receptive field. In the cortex the fall-off in detail with which the visual field is analysed, as one moves out from the foveal area, is accompanied not by a reduction in thickness of layers, as is found in the retina, but by a reduction in the area of cortex (and hence the number of columnar units) devoted to a given amount of visual field: unlike the retina, the striate cortex is virtually uniform morphologically but varies in magnification. In most respects the above description fits the newborn monkey just as well as the adult, suggesting that area 17 is largely genetically programmed. The ocular dominance columns, however, are not fully developed at birth, since the geniculate terminals belonging to one eye occupy layer IVc throughout its length, segregating out into separate columns only after about the first 6 weeks, whether or not the animal has visual experience. If one eye is sutured closed during this early period the columns belonging to that eye become shrunken and their companions correspondingly expanded. This would seem to be at least in part the result of interference with normal maturation, though sprouting and retraction of axon terminals are not excluded.

Anatomical and neurobehavioral investigations concerning the thalamo-cortical organization of the rat's visual system.

Abstract: The organization of thalamic afferents to the rat's visual cortex was investigated autoradiographically and through the retrograde transport of horseradish peroxidase (HRP) following injections into striate and peristriate cortex. The results revealed that Nucleus lateralis posterior (NLP) projects to a large peristriate cortical field that includes areas 18A, 7, and the anterior portion of area 18, and to a circumscribed temporal area corresponding to Krieg's ('46a,b) area 20. The dorsal lateral geniculate nucleus (LGNd) was shown to project to two spatially discontinuous cortical areas. The largest geniculate receiving area is partially coextensive with Krieg's area 17, but an extension of this projection posterior and medial to the striate cortex was found. In addition, a geniculate projection to a restricted field located in the lateral peristriate cortex was identified. Concurrent investigations were designed to assess the pattern discrimination abilities of rats prepared with striate cortical ablations, lesions in NLP and combined striate-cortical and thalamic ablations. Comparison of these animals with normal control subjects revealed that the striate cortex in the rat (as in the cat [Doty, '71; Sprague et al., '77] and the tree shrew [Killackey and Diamond, '71; Ware et al., '74]) is not necessary for successful pattern discrimination, and that the geniculo-striate and NLP-extra-striate projection systems are both involved in mediating the visual discriminative abilities of the rat. The results add species generality to the concept that the central connections to the visual cortex are characterized by parallel-conducting thalamic channels and contribute to the growing number of demonstrations that the extra-striate cortex and associated thalamic cell groups contribute significantly to the process of visual-pattern recognition.

Orientation columns in macaque monkey visual cortex demonstrated by the 2-deoxyglucose autoradiographic technique.

Abstract: IN the past fifteen years physiological studies of the primary visual cortex in higher mammals have provided evidence for two independent systems of functional subdivisions, ocular dominance columns and orientation columns1. These two systems are closely related to two important functions of visual cortex: combining at a single-cell level the information that originates in the two eyes, and rearranging the spatial information from the lateral geniculate body so that cells after the initial stage of visual processing come to respond to specifically oriented lines in the visual field.

Differential responsiveness of simple and complex cells in cat striate cortex to visual texture.

Abstract: The responsiveness of 254 simple and complex striate cortical cells to various forms of static and dynamic textured visual stimuli was studied in cats, lightly anaesthetised with N2O/O2 mixtures supplemented with pentobarbitone.

Effects of early experience upon orientation sensitivity and binocularity of neurons in visual cortex of cats.

Abstract: The class of neurons within the visual cortex of normal adult cats that has the smallest receptive fields (less than or equal to 2.25 degrees2) and that responds only to low rates of stimulus motion (less than or equal to 50 degrees / sec) responds preferentially to lines oriented about either the horizontal axis (+/-22.5 degrees) or the vertical axis (+/-22.5 degrees). In animals reared without exposure to patterned visual stimulation, many of these cells display orientation preferences but are activated monocularly. In contrast, in normal animals, neurons that have larger receptive fields or that respond to higher rates of stimulus motion do not exhibit a similar bias in the distribution of their orientation preferences. Cells of this type, studied in animals reared without exposure to patterned visual stimuli, are activated binocularly but do not display orientation preferences.

Magnification in striate cortex and retinal ganglion cell layer of owl monkey: a quantitative comparison.

Abstract: Magnification, the relative size of the neural representation of a portion of the visual field, decreases more rapidly with increasing visual field eccentricity in striate cortex than in the retinal ganglion cell layer of the owl monkey (Aotus trivirgatus); the proportion of the cells in striate cortex devoted to central vision is much larger than the comparable proportion of retinal ganglion cells. Magnification in striate cortex is a power function of magnification in the retinal ganglion cell layer. A formula for convergence (ganglion cells to cortical neurons) follows from this relationship.

Effects of cryogenic blockade of visual cortex on the responses of lateral geniculate neurons in the monkey

Abstract: Striate cortex in unanesthetized, paralyzed rhesus monkeys was cooled to assess the effects of temporary blockade of corticogeniculate fibers on responses of lateral geniculate neurons. Most neurons recorded under the thermode became inexcitable on cooling. After the onset of cooling, superficial layers became inexcitable before deep layers, and at a time when superficial activity was blocked, deep neurons were still orientation specific and retained this property until they themselves became inexcitable. Twenty-eight percent of the geniculate neurons projecting to cortex under the thermode were judged to be affected by cortical blockade, generally showing increases in driven and spontaneous activity. Cooling produced changes in the scale of response magnitude, rather than in the timing of impulse discharge, as evaluated by response time histograms. Responses evoked by bars or edges or by flashing spots were equally affected. The changes of activity produced were generally small and frequently difficult to differentiate from spontaneous shifts in excitability. In contrast, a visually driven inferior pulvinar neuron with a receptive field in the cooled area was strongly affected by cortical blockage, and driving quickly and completely returned soon after the cortex was rewarmed. It therefore appears that the method of blockade was effective but incapable of producing large effects in geniculate neurons. This suggests that cortical control may be inherently weak in the immobilized animal or that the distribution of activity between excitation and inhibition is equally balanced.

Corticocortical fiber connections of the rabbit visual cortex: a fiber degeneration study.

Abstract: Corticocortical fiber projections of the striate and occipital cortex of the rabbit, as defined by Rose ('31) have been determined by fiber degeneration methods following the production of cortical lesions within each of 24 rabbits. We have assumed that the striate and occipital cortices correspond respectively to the visual cortical areas 1 and 2 (V1 and V2) which have been demarcated electrophysiologically by Thornpson et al. ('50). A study of the ipsilateral fiber projections of the striate and occipital cortex of the rabbit reveals three distinct sets of associational corticocortical connections.(1) Neurons located in layers I-III of all regions of the striate cortex and the occipital cortex send fibers to terminate predominantly in layer V, but also in layers IV and VI, immediately beneath the cells of origin; however, the cells in the supragranular layers have not been found to send fibers to any other region of cerebral cortex. (2) The binocular portions of V1 and V2 appear to be interconnected ipsilaterally since cells in layers IV-VI of the lateral striate cortex have been shown to project to all layers of a restricted, adjacent portion of the medial occipital cortex; and the cells in layers TV-VIof medial occipital cortex send a similar, restricted projection to the adjacent lateral striate cortex. (3) Nerve cells in layers IV-VI of the lateral striate cortex (binocular Vl) send a restricted projection to the lateral portion of the occipital cortex. (4) After all lesions of the striate and/ or occipital cortices, degenerating fibers are seen radiating away from the lesion in layer I; the origin of these degenerating fibers could not be determined. The following observations have been made concerning the origins and terminations of commissural corticorticalfihers. (1) After ablation of most of the visual cortex of one side, commissural fibcrs are secn to terminate in all cortical layers in two narrow bands of visual cortex: one band occupies both sides of the striate-occipital boundary; the second band is found in the lateral portion of occipital cortex. (2) More punctate lesions reveal that commissural fibers arise from layers IV-VI of the lateral striate cortex and medial occipital cortex (binocular portions of V1 and V2 respectively) and end in hornotopic areas of the contralateral cortex.

Genetic instructions and developmental plasticity in the kitten's visual cortex.

Abstract: Two major properties of neurons in the kitten's visual cortex, binocularity and orientation selectivity, are present when the eyes first open, and therefore can be established by genetic instructions alone. However, both of these attributes require visual experience for their maintenance or strengthening; and both can be rapidly modified by unusual kinds of experience. Alternating sequences of cells dominated by one eye, then the other, can be recorded during penetrations through the cortex in binocularly deprived kittens, typical of the 'ocular dominance columns' of the normal adult cat. However, if one eye is deprived by lid-suture, the entire visual cortex becomes strongly dominated by the open eye. Experiments in which each eye saw separately through a transparent neutral density filter or a translucent diffuser showed that this phenomenon is caused not by the reduction in retinal illumination, but by the abolition of contrast in the deprived eye. A study of the retrograde transport of horseradish peroxidase from the visual cortex to the principal laminae of the lateral geniculate nucleus suggested that monocular deprivation from early in life may lead to a gross reduction in the distribution of afferent fibres from the deprived laminae. Previous experiments have found that if a kitten is exposed only to contours of one orientation, its cortical neurons become modified in their distribution of preferred orientations. This phenomenon was re-confirmed in a new study using a rigorously objective method of analysis.

Binocular differences in cortical receptive fields of kittens after rotationally disparate binocular experience

Abstract: Kittens were afforded visual experience only while wearing goggles fitted with prisms that rotated the inputs to the two eyes equally but in opposite directions about the visual axes (16 degrees for experimental subjects, 0 degrees for control subjects) Subsequently, receptive-field organization of the visual cortex was studied, special attention being given to the preferred orientation centered about the prism rotation experienced during early development Thus, for moderate amounts of relative rotation, the development of interocular matching of orientation specificity in binocular cells of the visual cortex reflects the correspondence of early visual input between the two eyes

Receptive field characteristics of neurons in a visual area of the rabbit temporal cortex.

Abstract: In a program of surveying the characteristics of visual receptive fields of neurons in rabbit brain, we have explored cortical sectors beyond the striate and occipital cortices and found cells in a part of the temporal lobe that were responsive to visual stimulation. Using evoked potential and unit-cluster methods, this temporal visual areas was mapped to be roughly oval-shaped, 3 mm × 2mm in size, and at about the level posterior to the apex region of auditory area 1. It is located ventral to and continuous with visual area 11, at about the caudal half of M. Rose's temporal cortices 1 and 2 (T1 and T2). Only about two-thirds of 96 units studied responded to some sort of moving light stimulation. These motion-sensitive cells were divided into four groups. Cells in the first group (22) responded best to a large light spot or shadow sweeping quickly across the field. Cells in the second group (29) responded to slow moving, jerking spot. Nine cells responded to a narrow, dark bar thrusting into a lighted field. Four cells are “direction-selective,” responding to light stimulus moving in one direction and showing either no response or decreased background discharges in the oppsite direction. In addition, three cells required unusual stimulus features. Of the 38 cells tested, nine of them were found to be binocularly driven. These receptive field characteristics are quite different from those described for other visual centers of the rabbit. The significance of these results together with data on the anatomical connections of this cortical area as reported in the following paper were discussed.

Thalamic inputs to the rabbit visual cortex: identification and organization using horseradish peroxidase (HRP).

Abstract: Horseradish peroxidase (HRP) has been injected in visual cortical area 1 (V1, striate cortex) of 33 rabbits (16 received a unilateral injection, 17 bilateral injections) in order to identify its thalamic inputs and to determine their retinotopic organization. This study has shown that when HRP is injected into different portions of V1: 1. Labeled cells are consistently seen in the dorsal lateral geniculate nucleus (LGNd) and are always organized into horizontal columns arranged perpendicularly to the long axis of the LGNd; although the columns are always present in the alpha sector of the LGNd, they extend into the beta sector of this nucleus only occasionally. 2. With a series of injection sites that lie on or near the medial edge of V1 and run rostrocaudally, cell columns shift from ventromedial to dorsolateral within the LGNd. With a series of injection sites that are located along the lateral border of V1 and run from rostral to caudal, columns of labeled cells move from ventral to dorsal along the medial edge of the LGNd. 3. In some of the experiments, with injections in either medial or lateral portions of V1, columns of HRP-labeled cells have also been found within the pulvinar.

Centrifugal and centripetal connections of the cat visual cortex.

Abstract: In experiments on curarized cats unit responses in the dorsal lateral geniculate body to stimulation of various zones in area 17 of the visual cortex were analyzed. Of all cells tested 69% were found to respond antidromically and 8% orthodromically; in 7.6% of cells IPSPs occurred either after an initial antidromic spike or without it. The velocities of conduction of excitation along the corticopetal fibers of the optic radiation varied from 28 to 4.3 m/sec, but the three commonest groups of fibers had conduction velocities of 28-19, 14-12, and 10-9.5 m/sec. A difference between latent periods of antidromic responses of the same neurons was found to stimulation of different zones of the visual cortex; this indicates that axons of geniculo-cortical fibers split into several branches which form contacts with several neurons in area 17 of the visual cortex. The degree and possible mechanisms of cortical influences on neurons of the lateral geniculate body are discussed.

Effect of binocular interaction of rat visual cortex neurons

Abstract: In anesthetized rats, out of 135 neurons recorded in binocular area within the striate cortex, 92 (74%) were binocular. 53 of these had well defined, mainly identical receptive fields on the two retinae. The range of relative horizontal and vertical disparity was found to be 5 degrees and 4 degrees respectively. These findings suggest that the visual system of the rat is capable to discover the spatial relationship using mechanisms of binocular fusion, in contrast to data obtained in rabbits.

Types of receptive fields of neurons in different laminae of the rabbit visual cortex

Abstract: Neurons of the primary rabbit visual cortex were classified into 7 large groups according to features of their receptive fields. The neurons with receptive fields were mostly revealed in the layers IV and VI, those with uniform directional receptive fields--in layer V, those with simple I-in layer VI, those with simple II--in layer II + III, and those with hypercomplex--in layer IV. The neurons with concentric receptive fields and those without responses to visual stimuli were equally distributed over the layers. The data obtained in rabbits, cats, and monkeys suggest that the tendency towards function stratification of primary visual cortex is successive in an evolutionary order of mammals.

Formation and functional significance of the dark receptive fields of the cat visual cortex

Abstract: Receptive fields (RFs) of single units in the 17th field of the visual cortex of immobilized cat were investigated under dark adaptation. The mean RF size was equal to 67 degrees and varied from 3 degrees up to 120 degrees. The RFs with centres located near gaze were from 3 degrees up to 120 degrees in dia, but with growth of excentricity the number of small RFs decreased, and in the region of 70 to 100 degrees from gaze only RFs with diameters equal to 100 degrees were found. The shape of "dark" RFs was either ellipsoidal (in most cases) or round. Detector properties (orientational, directional, size and velocity selectivity) of the "dark" RFs were significantly less manifest or absent. Under photopic light adaptation the same units reorganized their RFs to well known sizes and configuration. The hypothesis is discussed of the formation of local detector RF in the visual cortex in light adaptation by selective cortical inhibition which is activated in darkness only slightly. This view is an alternative to the commonly-accepted scheme of local cortical RF formation by the hierarchical and selective excitatory convergence.

Distribution of afferents from thalamic association nuclei in the occipital and parietal cortex in cats

Abstract: The laminar distribution of endings of thalamocortical fibers was studied in the parietal (area 7) and visual cortex (area 17) after ultrasonic destruction of the pulvinar, by the Fink-Heimer method and by electron microscopy. Degenerating fibers and their endings were found in the parietal cortex in all layers, with the greatest concentration in layers III–V. In the visual cortex fibers from the pulvinar terminate chiefly in layer IV. Degenerating fibers terminate on spines and thin branches of dendrites in both the parietal and the visual cortex.

Cyclic groups and adaptation in the visual system of the cat

Abstract: Publisher Summary The striate cortex responds to illumination at a specific retinal field, which has a light or dark line or an edge at a specific angle, as the preferred visual stimulus (PVS). This is the result of the simple cell's connection to several lateral geniculate cells, which together have this linear spatial relation as their combined retinal field. These are found in the same or neighboring columnar location, complex cells that respond to the same PVS as the nearby simple cells but for a much extended retinal field. They have indirect evidence that this is because of connections from several simple cells to a complex cell. Polymodal neurons have a primary response to specific light stimuli, but they also respond to one or several other modalities: sound, shock, vestibular, and altered light stimulation. These neurons are found in the lateral geniculate body, in the striate, and in the parastriate visual cortex of the cat. 10–15% of polymodal neurons in the parastriate cortex of adult cats are plastic cells because if the PVS is coupled to one of the other modality stimuli, the response is altered. This is observed in the histograms of unit responses versus time after stimulation.