Showing papers on "Orientation column published in 1985"

Intracortical facilitation among co-oriented, co-axially aligned simple cells in cat striate cortex.

Abstract: Most neurons in cat striate visual cortex show inhibitory effects when moving contours are presented beyond the limits of classic receptive field regions. Facilitatory effects are also present in about 40% of simple cells. Here, we report a highly specific form of this facilitation, mediated only by neurons possessing both an orientation tuning matched to the test unit, and a receptive field position aligned with its long axis. This finding illustrates one of the intracortical interconnection schemes hypothesized by Mitchison and Crick (1982). Periodic clustering in long, intrinsic axons may signify a neuron seeking specific functional interactions like these across columnar systems in both the spatial and orientation domains.

The mapping of visual space onto foveal striate cortex in the macaque monkey

Abstract: Visuotopic maps of foveal striate cortex have been obtained by means of single cell recordings from four hemispheres in two awake, behaving macaque monkeys. The numbers of successful separate striate penetration sites in the four hemispheres were 42, 58, 81, and 61, for a total of 242. The resolution of the maps is 10 min of visual angle, nearly an order of magnitude finer than previous maps. No striate receptive field center was found more than 5 min into the ipsilateral visual field. The four maps were sufficiently compatible with one another that they could be combined into one. There are only minor magnification differences between the right and left hemispheres and between the upper and lower quadrants. There is a vertical/horizontal magnification anisotropy of about 1.5:1 in central foveal cortex (0 to 20 min). The composite map can be approximated by the complex logarithmic equation, w = 7.7 * ln (x + iy + 0.33), where w is expressed in millimeters and x and y are expressed in degrees.

Anatomical organization of primary visual cortex (area 17) in the ferret.

Abstract: The present report describes the intrinsic and extrinsic cortical connectivity of striate cortex (area 17) in the ferret. Injections of horseradish peroxidase demonstrate periodic intrinsic connections over an extent of 2.5-3.0 mm, mainly in the supragranular layers but also occurring secondarily in layer 5. These connections have a stripelike configuration, with a center-to-center spacing of 0.5-0.7 mm. Their laminar distribution and stripelike configuration resemble the pattern in the cat (Gilbert and Wiesel, '83), another member of the carnivore family, but not that in monkeys. In both macaque and squirrel monkeys, these connections have a bilaminar distribution in layers 2-3 and 4B, and a more complicated latticelike geometry (Rockland and Lund, '83). Their interperiod spacing, of about 0.5 mm, however, is relatively constant across species. Extrinsic connections in the ferret link striate cortex with territories probably homologous to feline areas 18 and 19, and to the suprasylvian region. Callosal connections extend on the lateral surface about 1.5 mm into area 17 and 4.0 mm into area 18 beyond their common border. There are homotopical connections between striate cortices and heterotopical connections from at least areas 18 and 19 to contralateral area 17. In addition to gray matter connections, intracortical injections also result in labeled interstitial neurons in the subgriseal white matter. These occur both subjacent to an injection site in area 17, and below labeled foci in area 18 projecting back to area 17, as if interstitial neurons shared the connectivity of overlying layer 6.

Intrinsic projections within visual cortex: evidence for orientation-specific local connections.

Abstract: The functional organization of intrinsic connections within area 18 of cat visual cortex was studied using combined electrophysiological and anatomical techniques. Physiological recordings were first used to map the distribution of orientation preference, ocular dominance, and receptive-field location relative to the cortical surface. Next, localized injections of lectin-conjugated horseradish peroxidase were made into physiologically identified regions within area 18. We found that (i) the local cortical interconnections are made preferentially between cell populations with orthogonal preferred orientations and are independent of the ocular dominance of the cortical cells, (ii) the map of visual space in the cortex is anisotropic with the magnification factor for vertical at least twice that for horizontal visual space, and (iii) the pattern of cortical projections compensates for the functional asymmetry so that a population of interconnected cells represents a roughly circular region of visual space.

Large layer VI cells in macaque striate cortex (Meynert cells) project to both superior colliculus and prestriate visual area V5.

Abstract: Layer VI of macaque striate cortex contains a number of large solitary neurones called Meynert cells. It has been shown earlier that these Meynert cells project to the posterior bank of the superior temporal sulcus (area V5), but it has also been shown that they project to the superior colliculus. In retrograde fluorescent double-labelling experiments, it was found that Meynert cells represent a class of neurones which distribute divergent axon collaterals to the posterior bank of the superior temporal sulcus and to the superior colliculus, i.e. to a distant cortical and a subcortical structure. This feature appears to be unique among projecting neurones in monkey visual cortex.

Motion after-effects in cat striate cortex elicited by moving gratings.

Abstract: Responses of striate cortical neurones to bars of optimal orientation and width, moving with fixed velocity, were recorded in the lightly anaesthetized cat. Effects of periods of pre-adaptation with square-wave gratings of variable spatial frequency and velocity, drifting continuously in each cell's preferred or null directions, were investigated. Variations of cells' directional bias and responsiveness to oriented bars were assessed in relation to the degree and time-course of pre-adaptation to drifting gratings, compared with the preceding level of firing when exposed to uniform backgrounds of the same average luminance. All cells showed some susceptibility to pre-adapting moving gratings: subsequent responses to a bar were initially depressed in the direction of pre-adaptation and, in direction-biased or bidirectional cells, were enhanced in the opposite direction, compared with bar responses following exposure merely to a uniform background. These effects were strongest and most consistent amongst standard complex cells and weakest amongst special complex cells: maximal effects were obtained with adapting gratings of optimal velocity and spatial frequency.

An overall description of retinotopic mapping in the cat's visual cortex areas 17, 18, and 19

Abstract: Mathematical functions are derived which model the retinotopic mapping in the cat's visual cortical areas 17, 18, and 19. All three mappings are simple modifications of a complex power function with an exponent of 0.43. This function is decomposed so as to give an intermediate stage which is common to all three mappings and can be regarded as a model of the lateral geniculate nucleus mapping. The influence of retinotopic mapping on visual receptive fields was studied. The results show that a dependence of the receptive field properties on the position in the visual field is to be expected.

Functional organization of the cat's visual cortex after prenatal interruption of binocular interactions

Abstract: The functional consequences of interrupting in utero binocular interactions were studied by recording from single cells in area 17 of adult cats that had one eye removed at least 2 wk before birth. In these animals all cortical neurons could be driven by the remaining eye, and in tangential microelectrode penetrations, sequences of neurons containing a full 180-degree cycle of preferred orientations were encountered. Other response properties of cortical neurons in the prenatally enucleated animals were also normal with the notable exception that the dimensions of receptive fields were significantly smaller when compared with those of control animals. Our results indicate that orientation columns in the visual cortex can develop independently of ocular dominance columns, and they suggest that interruption of binocular interactions during prenatal development of the visual pathways may enhance the resolving power of the remaining eye.

Development of cortical afferents and cortico-tectal efferents of the mammalian (rat) primary visual cortex.

Abstract: At the time when the fibres from the striate cortex (area 17) begin to innervate the superficial layers of the superior colliculus of the young rat (postnatal days 4 and 5) a high degree of specificity in the organization of this newly formed cortico-tectal projection is already apparent. Thus, in young rats, as in adult mammals of virtually all species studied so far, the somata of cortico-tectal neurones are confined to lamina V of the ipsilateral cortex. However, this high degree of laminar (radial) specificity in young animals is accompanied by a substantial degree of exuberance as indicated by a tangential distribution of the cortico-tectal cells which is wider than that in the adult. The exuberant projections are pruned during the second postnatal week. The cortico-cortical associational and commissural fibres start to enter the grey matter of the rat striate cortex after postnatal day 7. Again a high degree of specificity in the laminar distribution of those newly established projections is apparent. However, the cortico-cortical projection, at the time when cortico-cortical fibres enter the cortical laminae, is clearly exuberant since the tangential spread of cortical cells projecting to the striate cortex is wider than that in the adult. Pruning of these excessive projections takes place some time after postnatal day 14. It is believed that understanding the mechanism(s) underlying the development of connections of the rat visual cortex might be of general importance in understanding developmental abnormalities in the pattern of interconnections of the visual cortices of other mammalian orders.

Modification of callosal afferents of the primary visual cortex ipsilateral to the remaining eye in rats monocularly enucleated at different stages of ontogeny.

Abstract: Callosal afferents to the primary visual cortex (area Oc1) mainly originate in the border region between the lateral portion of the primary visual cortex (area Oc1) and the laterally positioned secondary visual cortex (area Oc2L) of the contralateral hemisphere. The extent of this region has been determined by retrograde labeling with horseradish peroxidase (HRP). In normal rats the width of the retrogradely labeled cortical strip is about 0.3 mm. In rats monocularly enucleated from the 23rd up to the 44th ontogenetic day and subsequently injected as adults with HRP into Oc1 ipsilateral to the remaining eye, the perikarya of the callosal afferents from the opposite hemisphere are labeled in the form of significantly wider columns (about 0.8 mm) than in animals enucleated from the 50th ontogenetic day onwards. The latter do not differ from controls.

The character and influence of the claustral pathway to the striate cortex of the cat

Abstract: 1. In paralyzed and anaesthetized cats, the pathway running from the claustrum to the striate cortex was characterized from the transynaptic latencies of responses that were initiated by electrical stimulation in the claustrum (CL) and recorded extra-cellularly in single striate neurons. A second stimulating electrode (OR1) in the primary visual pathway provided information on the input coming to the recorded cell from the lateral geniculate nucleus. 2. An analysis of the classified striate neurons receiving a claustral drive revealed that 68% were C cells and 26% were S cells. For the C cells, 81% had CL latencies of less than 2.5 ms (mean = 1.8 ms) and the potential to receive a direct drive from a fast conducting input; the remaining 19% had latencies around 3.0 ms (mean = 3.0 ms), a value consistent with a disynaptic input from the same type of input. 3. From their CL latencies, the S cells also could be subdivided into two subgroups; one, made up of 36% of the sample had CL latencies of less than 2.5 ms (mean = 1.9 ms) and the capacity, like the majority of C cells, to receive a direct, fast-conducting input; the second subgroup, consisting of 74% of the S cells, had CL latencies longer than 3.0 ms (mean = 5.4 ms). 4. The majority of cells with a claustral-drive (85%) were encountered either in laminae 4 or 6. Claustral-driven cells belonging to both S and C catagories were found in the two laminae (4 and 6) and there was no observed predisposition for a particular cell type to cluster in either of these lamina. 5. From a comparison of CL and OR1 latencies, justified on the grounds of independent stimulation, a strict correlation was found for signal conduction properties in the claustral and LGN pathways running to a given striate neuron. 6. From a quantitative evaluation of receptive field properties the claustral-driven striate neurons were found to resemble cells in the general population. As a group, however, they were distinctive in that both end-zone inhibition and direction selectivity were either weak or absent from the cell's response. This finding held for cells in both the C and the S categories. 7. It is concluded from the high incidence of claustral-driven C cells, that the claustral loop from the striate cortex is involved in an aspect of motion detection.

Standardness and invariability of the detector tuning of neurons in the orientation column of the visual cortex of the cat

Abstract: The variability of neuron orientation tuning in separate columns and the degree of it stability under changes in levels of the contrast between stimulus and background were studied in experiments on unanesthetized, relaxed cats. Several types of orientation columns were revealed: with a relatively high, standard and stable orientation tuning; with a widely changing orientation tuning from neuron to neuron; with invariance to contrast level; with variant orientation tuning; with mixed (invariant-variant) properties. In the columns, standard-nonstandard properties, on the one hand, and properties of invariability-variability, on the other hand, could combine in different ways. More often differences of orientation tuning within a column were observed between neurons of upper and lower cortical layers. Possible distinctions in the functional role of types of orientation tuning in columns described and in mechanisms of formation of detector properties of their neurons are discussed.

Study of afferent connections of the visual cortex in the ventral bank of the cruciate sulcus in cats by the method of retrograde axonal transport of horseradish peroxidase

Abstract: To study the possible pathways along which visual signals reach a visual zone discovered by the writers in the cat frontal cortex in the ventral bank of the cruciate sulcus, horseradish peroxidase was injected into a site previously identified by physiological experiments. Stained neurons were discovered in visual areas of the cortex (lateral suprasylvian and ectosylvian), in the parietal cortex (areas 5 and 7), and also in small numbers in the prefrontal and limbic cortex. Stained neurons were found in the following nuclei in the thalamus: n. medialis dorsalis, intralaminar nuclei (nn. centralis lateralis, paracentralis, centralis medialis), nn. ventralis medialis, anteromedialis, and reuniens. Many stained neurons were found in the claustrum and a few in the substantia grisea centralis in the midbrain. The principal sources of inputs to the cortical area investigated are thus centers of the visual system or parts of the brain directly connected with it.

Distribution of Cholecystokinin-containing Neurons in Cat Visual Cortex

Abstract: The visual cortex has been well studied anatomically and physiologically,’ but information on neurotransmitters used by cortical neurons, especially the interneurons, is still scarce. Up till now, only glutamic acid decarboxylase immunoreactivity (GAD-IR) has been demonstrated in the short-axon cells of cat visual cortex; 8-1 5% of these cells contain GAD-IR.’ As cholecystokinin (CCK) may play a role in the release of GABA,’ we have examined the laminar distribution of CCK in areas, 17, 18, and 19 of cat visual cortex. Four cats were injected with colchicine; two cats were untreated. CCK-immunoreactive nerve fibers and perikarya were found in both the untreated and colchicineinjected cats although the staining of the cells was more intense in the colchicinetreated animals. Immunoreactive cells were identified according to their dendritic pattern, as described by A. Peters and J. R e g i d ~ r . ~ All CCK-positive neurons were nonpyramidal cells, representing + 0.5-0.6% of the neuronal population of cat visual cortex. Cell bodies were spread throughout the cortex, but concentrated in the supragranular layers (FIG. l), where we also found an intrinsic plexus of CCKimmunoreactive nerve fibers. According to their dendritic pattern, the CCK-positive cells could be identified as multipolar or bitufted neurons. Only a few clear examples of bipolar neurons amongst the CCK-immunoreactive cells were found. The bitufted neurons can be classified into two groups: 1) the horizontally oriented neurons of layer I (width +15 pm, length k25 pm), with dendritic fields parallel to the pial surface (FIG. 2A). 2) the vertically oriented neurons of layers I1 and 111 (width k 13 pm, length k25 pm) most common at the border with layer I (FIG. 2B). Primary dendritic trunks arise from each pole of the perikaryon and divide into daughter branches which eventually pass into layer I. The remaining CCK-positive cells in layers I-VI are round or irregularly shaped (+20 pm) (FIG. 2C). Several dendritic trunks emanate nonpreferentially from the soma, especially in layer VI, where dendrites arise from the lateral portion of the horizontally oriented soma. The distribution pattern and the morphology of the different cell types was the same in the three visual areas examined. In all three areas about 92% of the CCK-positive neurons were found in the supragranular layers. As CCK may facilitate the release of GABA, and, as GABA has an important functional role in the visual cortex: CCK could be important in visual processing, especially in the supragranular layers.

Laminar distribution of neurons with different types of receptive fields in the rabbit visual cortex

Abstract: Investigation of receptive fields of 232 primary visual cortical neurons in rabbits by the use of shaped visual stimuli showed that 21.1% are unselective for stimulus orientation, and 34.1% have simple, 16.4% complex, and 18.5% hypercomplex receptive fields, and 9.9% have other types. Neurons with different types of receptive fields also differed in spontaneous activity, selectivity for rate of stimulus movement, and acuteness of orientational selectivity. Neurons not selective to orientation were found more frequently in layer IV than in other layers, and very rarely in layer VI. Cells with simple receptive fields were numerous in all layers but predominated in layer VI. Neurons with complex receptive fields were rare in layer IV and more numerous in layers V and VI. Neurons with hypercomplex receptive fields were found frequently in layers II + III and IV, rarely in layers V and VI. Spontaneous unit activity in layer II + III was lowest on average, and highest in layer V. Acuteness or orientational selectivity of neurons with simple and complex receptive fields in layers II + III and V significantly exceeded the analogous parameter in layers IV and VI.

Visual cortical detector neurons in the Siberian chipmunkEutamias sibiricus

Abstract: Three functional classes of neurons are described in the visual cortex of the Siberian chipmunk: neurons not selective for direction of movement and orientation, neurons selective for movement in a particular direction, and neurons selective for orientation. Unselective and directionally-selective neurons were activated maximally at speeds of movement of 100–500 deg/sec or more, most orientation-selective neurons at speeds of 10–50 deg/sec. For all three classes of neurons clear correlation was observed between selectivity for velocity of movement and character of responses to presentation of stimuli stationary in the receptive field. With reference to this sign the neurons were divided into two groups: phasic (fast) and tonic (slow). Phasic (fast) neurons predominate in the visual cortex ofEutamias sibiricus.

Standardization and invariance of neuronal detector tuning in an orientation column of the cat visual cortex

Abstract: Variability of orientation tuning of primary visual cortical neurons in single orientation columns and the degree of its stability during changes in the level of contrast between stimulus and background were investigated in acute experiments on immobilized cats. Several types of orientation columns were found, with the following properties of orientation tuning of their neurons: relatively high, standard, and stable; varying widely from neuron to neuron; invariant regardless of the level of contrast; noninvariant; mixed (invariant-noninvariant). Properties of standardization-nonstandardization, on the one hand, and invariance-noninvariance of the neurons, on the other hand, may be combined differently in a column. Differences of orientation tuning within a column were observed most frequently in neurons of the upper and lower layers of the cortex. Possible differences in the functional role of the variance of orientation columns described and in the mechanisms of formation of the detector properties of their neurons are discussed.