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At least 19 recordsLinked to original sources
PubMed1987

Molecular markers of neuronal subpopulations in layers 4, 5, and 6 of cat primary visual cortex.

Cat primary visual cortex has been used as an immunogen to produce monoclonal antibodies that detect subpopulations of neurons. When tested by immunofluorescence on tissue sections of areas 17 and 18, 2 of these antibodies, VC1.1 and VC5.1, outlined a rare subpopulation of neurons located mainly in layer 4 but also in layers 5 and 6. Double-labeling immunofluorescence experiments in area 17 revealed that all VC1.1-reactive cells were also VC5.1-reactive and 83% of VC5.1-reactive cells were VC1.1-reactive, suggesting that the antibodies were reacting with the same subpopulation of cells. Both antibodies labeled similar or identical subpopulations of cells in other areas of the cat CNS, including the superior colliculus, parts of hippocampus, cerebellar deep nuclei, and rostral spinal cord. Neither antibody labeled cell bodies in the lateral geniculate nucleus. In the retina, VC1.1 labeled cell bodies and processes of some horizontal and amacrine cells, whereas VC5.1 labeled only ganglion cell axons. In the cerebellar cortex, the most prominent labeling of VC1.1 was of Purkinje cells, whereas that of VC5.1 was of Lugaro cells. Immunoblotting analyses of cat cortical homogenates demonstrated that VC1.1 recognized a major polypeptide band of Mr 95,000-105,000 and additional bands of Mr 145,000 and Mr 170,000. VC5.1 recognized bands of Mr 97,000 and Mr 150,000. Subcellular fractionation and extraction studies showed that the VC1.1 antigens were integral membrane proteins preferentially located in a synaptosomal plasma membrane fraction. The VC5.1 antigens were preferentially located in a soluble cytoplasmic or extracellular fraction. The results indicate that antibodies VC1.1 and VC5.1 recognize unique epitopes in the cat CNS and define a previously unrecognized subpopulation of cells in cat visual cortex.

Animals↗
PubMed1990

Ultrastructure of PkC(II/III)-immunopositive structures in rat primary visual cortex.

In the primary visual cortex of adult rats the cellular and subcellular distribution of protein kinase C isozymes II and III (PkCII/III) was examined by immunohistochemical methods with a monoclonal antibody against PkCII/III. Strong PkC(II/III)-immunoreactivity was found in neurons and astrocytes. Immunopositive neurons exhibited morphological features characteristic for both pyramidal and non-pyramidal cells. They were distributed in layers II through VI but were concentrated in layers II/III. At the electron microscopic level immunoprecipitate was found predominantly in distinct regions of the somata, except the nuclei, and only a few labeled dendrites and axons were seen. Two different patterns of cytoplasmic immunoreactivity could be distinguished. In most neurons, PkC(II/III)-staining was confined to cytoplasmic spots associated with the Golgi complex, while a few neurons exhibited additional labeling in the vicinity of the cell membrane. Moreover, PkC(II/III)-immunoreactivity was present in numerous astroglial processes and in the perikaryal cytoplasm of a subpopulation of astrocytes. The present data provide morphological indications for specific functions of PkC isozymes II and III in neurons as well as in astrocytes.

Animals↗
PubMed1987

Morphology of corticotectal cells in the primary visual cortex of hooded rats.

In primary visual cortex of hooded rats, pyramidal cells in layer V may be classified as long, medium, or short, on the basis of the layer in which the apical dendrite terminates. The present study determines which of these types of pyramidal cells project to the superior colliculus. Two different strategies were used to label corticotectal cells with horseradish peroxidase (HRP). In the first set of experiments, a large number of corticotectal cells were labeled by retrograde transport following injection of HRP into the superior colliculus. In the second set of experiments, single unit recording was used to identify corticotectal cells physiologically by antidromic activation from the superior colliculus. These cells were then impaled and labeled by intracellular iontophoresis of HRP. The results from both techniques suggest that only long pyramidal cells send an axon to the superior colliculus. These cells are distinguished by an apical dendrite that extends into layer I. We conclude that in hooded rats corticotectal cells in primary visual cortex are the long pyramids in layer V.

Action Potentials↗
PubMed1979

The rabbit and the cat: a comparison of some features of response properties of single cells in the primary visual cortex.

Receptive field characteristics of single cells in primary visual cortex of rabbit were studied. Seventy-two percent of cells were found to be orientation selective, and the remainder had concentric, uniform, movement selective or pure direction selective receptive fields. Single cells were also recorded from primary visual cortex of cat to permit a comparison of visual cortical organization in cats and rabbits. Laminar organization of receptive field types was observed in rabbits which was similar in most respects to that described in the cat. Although the major categories of orientation selective cells (simple, complex, hypercomplex) were similar for both cat and rabbit, many differences emerged: (I) tuning of orientation selectivity was narrower in cats than in rabbits; (II) units which preferred oblique orientations were less frequently represented in rabbits than in cats; (III) orientation preferences appeared to be arranged in clusters in rabbit cortex; in rabbits we found no evidence of the columnar organization of orientation selectivity which characterizes cat visual cortex. A comparison of our data with those previously reported for mouse, rat, hamster and opossum visual cortex suggest that mammals in which a significant proportion of visual cortical cells are not orientation selective have in common certain patterns of cortical organization involving a less precise and less specilized representation of stimulus orientation.

Animals↗
PubMed1989

Evidence for a dopaminergic innervation of cat primary visual cortex.

Experiments have been conducted to determine whether dopamine fulfills the criteria to be considered as a neurotransmitter in cat primary visual cortex. N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine, a neurotoxin with high selectivity for noradrenergic terminals, was administered into kitten cerebral ventricles. Two weeks later, the concentration of norepinephrine in visual cortex was reduced to 15% of control while dopamine and serotonin were not depleted. Receptor binding assays with [3H]SCH 23390 showed that membranes prepared from cat primary visual cortex contain a binding site that has the properties of a D1 receptor. This site was localized by autoradiography to two bands, one in layer VI and the second in upper layers of visual cortex. A dopamine-stimulated adenylate cyclase activity was demonstrated that was inhibited by SCH 23390 but not by alprenolol. Norepinephrine was shown to stimulate adenylate cyclase activity through both a beta-noradrenergic receptor and a D1 receptor. Binding assays with [3H]spiperone indicated that D2 dopamine receptors are absent from cat visual cortex or present in very low amounts. Taken together these results strongly suggest the existence of a dopamine innervation of cat primary visual cortex. The neurotoxin experiments show that some of the dopamine in cat visual cortex is not in noradrenergic terminals while the receptor assays demonstrate the presence of D1 receptors functionally linked to the synthesis of cyclic 3',5'-adenosine monophosphate. The demonstration of a dopaminergic innervation in cat primary visual cortex is also relevant to the interpretation of data on the involvement of catecholamines in developmental plastic phenomena.

Adenylyl Cyclases↗
PubMed1991

Synaptogenesis in the primary visual cortex of the tree shrew (Tupaia belangeri).

The primary visual cortex of the tree shrew is characterized by the lack of ocular dominance columns. The two eyes are represented in sublayers of laminae 3 and 4. In an earlier study using the transneuronal transport we observed that the geniculate afferents from the two eyes do not initially overlap and then segregate into their appropriate sublaminae. The final distribution pattern can already be observed during the early postnatal period. Since segregation and elimination of afferent terminal branches do not seem to take place, we wanted to investigate whether or not an overproduction of synapses can be observed as in several other animals. We examined layers 3B, 3C, 4A, and 4B, which receive afferents from the retina via the lateral geniculate nucleus, from P5 to maturity by using the electron microscope. The brain tissue was excised in the region where the central vision is represented in adult animals. Then we determined the density of synapses per 100 microns 2 neuropil for each of the four sublayers at the ages P5, P15, P19, P23, P31, and P42 and in the adult animal (AD). In determining the neuropil we measured the size of two additional compartments, i.e., the compartments consisting of perikarya and of blood vessels. At a higher resolution we determined the fraction of Gray type I and type II synapses in each sublamina and in each developmental stage. The size of the neuropil increases from 57% at P5 to 81% in AD whereas the compartment of perikarya decreases from 42% to 15% and the compartment of blood vessels increases from 1.3% to 3.9%. The synaptic density starts with very low values (3.5/100 microns 2) at P5. Then it increases rapidly and attains a maximal rate of increase during the period of eyelid opening. After this period the increase is slowed down and approaches the adult value (12.5/100 microns 2) slowly. An overproduction of synapses could not be observed. The percentage of type I and type II synapses also changes during this period. The fraction of type I synapses amounts to 73% at P5 and increases to 92% in AD. The increase in density of type I synapses is continuous and does not show any sign of overproduction. The density of type II synapses rapidly reaches it final value and then remains constant. Possibly there is a slight overproduction during the period of eyelid opening.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

A mathematical model of the primary visual cortex and hypercolumn.

A mathematical model of the primary visual cortex is presented. Basically, the model comprises two features. Firstly, in analogy with the principle of the computerized tomography (CT), it assumes that simple cells in each hypercolumn are not merely detecting line segments in images as features, but rather that they are as a whole representing the local image with a certain representation. Secondly, it assumes that each hypercolumn is performing spatial frequency analyses of local images using that representation, and that the resultant spectra are represented by complex cells. The model is analyzed using numerical simulations and its advantages are discussed from the viewpoint of visual information processing. It is shown that 1) the proposed processing is tolerant to shifts in position of input images, and that 2) spatial frequency filtering operations can be easily performed in the model.

Depth Perception↗
PubMed1992

Calretinin-immunoreactive neurons in the primary visual cortex of dolphin and human brains.

A new class of gamma-aminobutyric acid (GABA)ergic neurons immunoreactive to the calcium-binding protein calretinin (CR) was demonstrated in primary visual cortices of the bottlenose dolphin (Tursiops truncatus) and humans (Homo sapiens). Comparative analysis revealed several differences between dolphin and human visual cortex in the laminar distribution of CR-positive perikarya, although general typology of the immunoreactive CR-positive neurons was similar in both species. Thus, in both human and dolphin primary visual cortex almost all CR-positive neurons are non-pyramidal, either fusiform or bipolar cells, oriented with their long axis along the radial axis of the cortex. Large multipolar stellate cells were also observed in layers I and VI. The CR-positive neurons in the dolphin visual cortex are concentrated almost exclusively in layer I and, to a lesser extent, in layer II. In all other layers (IIIa, b, IIIc/V and VI) of the dolphin visual cortex CR-positive neurons were only rarely seen. In the human primary visual cortex CR-positive neurons are located mainly in layers II, III and IVa, b, c, with considerably lower densities of these cells observed in layers V and VI. CR-positive neurons in layer I of the human visual cortex are represented by Cajal-Retzius horizontal cells, whereas no such cells were seen in layer I of the dolphin neocortex. The numerical density of CR-positive neurons in the dolphin primary visual cortex is significantly lower than in the area of cortex in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Synaptic organization of serotonin-immunoreactive fibers in primary visual cortex of the macaque monkey.

The macaque neocortex is very densely innervated by serotonin-containing fibers. The highest density of these fibers is in primary sensory regions such as the primary visual cortex. By using an antibody against serotonin, we analyzed the distribution and morphology of serotonin-immunoreactive fibers and synapses in the primary visual cortex of the adult cynomolgus monkey. In addition, we quantified the laminar distribution of labeled varicosities and the distances between varicosities in single fibers. While serotonin-immunoreactive fibers are found in all cortical layers, at least three bands of heightened density of innervation were readily recognized that were coincident with 1) layer IIIB to IVC alpha, 2) layer VA, and 3) layer VIB. Layer IVC alpha of area 17 contained more varicosities per unit area than any other sublayer. There was a high degree of variability in the intervaricosity distances along single fibers; more than half were longer than 10 microns. At the electron microscopic level, synaptic contacts were also observed throughout the entire thickness of area 17, with the highest frequency in layer IV. The labeled varicosities were packed with electron-lucent synaptic vesicles and formed synaptic complexes with small, but conspicuous, post-synaptic densities. Dendritic shafts were the most common postsynaptic target of the labeled synapses. Among these characteristically slender post-synaptic shafts, profiles with structural features of both spiny and smooth dendrites were observed. The small diameter of most of the postsynaptic dendrites indicated that distal dendrites were preferentially contacted by serotonin-immunoreactive varicosities. Although direct identification of the postsynaptic neurons will be required for complete characterization of this circuitry, the distribution of serotonin-immunoreactive varicosities suggests that serotoninergic interactions in the primary visual cortex of the cynomolgus monkey are directed predominantly at the distal dendrites of granular and infragranular neurons rather than at targets in the supragranular layers.

Animals↗
PubMed1990

Electrophysiological properties of embryonic neocortex transplants replacing the primary visual cortex of adult rats.

Solid pieces of the occipital neocortex derived from 17-day rat fetuses were placed in a cavity formed by complete unilateral aspiration of the primary visual cortex in adult rats. Vital labeling of the brain with bisbenzimide was used to differentiate grafts from the host brain tissue. 2 to 10 months after operation electrophysiological experiments were performed in which neuronal activity and field potentials in transplants were recorded in response to sensory and electrical stimulation of the host brain. This study shows that in a large portion of the transplants (14 out of 25): (1) the majority of neurons (183/270) are controlled by visual stimuli and many of them respond to electrical stimulation of the lateral geniculate body (53/62) and the homotopic sites of the contralateral neocortex (28/62); latencies of these responses are within the ranges typical of the normal visual cortex; (2) there is a topical representation of the visual field on the transplants; (3) receptive field sizes, the preference to stationary flashes or to moving visual stimuli and the temporal response pattern of the grafted neurons are similar to those of the primary visual cortex. However, the field potentials evoked visually were recorded only in part of the transplants (8/14) which revealed clear neuronal visual responses, and field potential depth profile differed from that in visual cortex in situ. The functional organization of the transplants remained unchanged throughout the long-time testing. Taken together, these results suggest that after primary visual cortex removal, fetal neocortex transplants may be able to replace functionally the damaged neural circuitries of the host brain.

Animals↗
PubMed1985

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

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.

Afferent Pathways↗
PubMed1992

Dynamic changes in receptive-field size in cat primary visual cortex.

Immediately after focal retinal lesions, receptive fields (RFs) in primary visual cortex expand considerably, even when the retinal damage is limited to the photoreceptor layer. The time course of these changes suggests that mere lack of stimulation in the vicinity of the RF accompanied by stimulation in the surrounding region causes the RF expansion. While recording from single cells in cat area 17, we simulated this pattern of stimulation with a pattern of moving lines in the visual field, masking out an area covering the RF of the recorded cell, thereby producing an "artificial scotoma." Over approximately 10 min this masking resulted in a 5-fold average expansion in RF area. Stimulating the RF center caused the field to collapse in size, returning to near its original extent; reconditioning with the masked stimulus led to RF reexpansion. Stimulation in the surrounding region was required for the RF expansion to occur--little expansion was seen during exposure to a blank screen. We propose that the expansion may account for visual illusions, such as perceptual fill-in of stabilized images and illusory contours and may constitute the prodrome of altered cortical topography after retinal lesions. These findings support the idea that even in adult animals RFs are dynamic, capable of being altered by the sensory context.

Animals↗
PubMed1987

Dopaminergic innervation of the primary visual cortex in the rat, and some correlations with human cortex.

Dopaminergic terminals have been identified in the primary visual cortex with three techniques; immunocytochemistry with an anti-dopamine antiserum, retrograde axonal transport techniques using unconjugated wheat germ agglutinin and HPLC determination of catecholamines and metabolites in microdissected sub-regions of occipital cortex in the rat. The results demonstrate a specific dopaminergic innervation, arising from the ventral tegmental area, which is found mainly in laminae VI and V, but with minor innervation also in lamina I. Dopaminergic innervation to adjacent cortical regions is also described. Neurochemical data from post-mortem human material suggests that a similar innervation exists in man. An analysis of the distribution of dopaminergic fibres in relation to the known connections and possible functions of the deep laminae of visual cortex suggests that dopaminergic axons may participate in the corticofugal control of visual afferent pathways.

Aged↗
PubMed1990

Numbers of "blobs" in the primary visual cortex of neonatal and adult monkeys.

We have examined the number of "blobs" (cytochrome oxidase-positive cortical modules) in the primary visual cortex (area 17) of infant and adult rhesus monkeys. The density of these iterated circuits--about five per mm2--was not significantly different in three newborn and three mature animals. Measurement of the surface of area 17 in serial sections, however, showed that the total area occupied by the primary visual cortex increases by about 50% during maturation. Based on these measurements, the number of blobs in this species is about 8000 at birth and about 12,000 in maturity. Evidently, these complex functional units are added gradually to the developing primate brain over a period that extends into postnatal life.

Aging↗
PubMed1988

Ramification patterns of vasoactive intestinal polypeptide (VIP)-cells in the rat primary visual cortex. An immunohistochemical study.

Vasoactive intestinal polypeptide (VIP)-immunoreactive cells in the primary visual cortex of the rat were classified on the basis of ramification pattern of cell processes. The distribution of cells over cortical layers, and proportions of cell classes relative to total cell numbers were evaluated by means of quantitative methods. Two main types of VIP-positive neurons, the bipolar and the multipolar were distinguished constituting 76% and 24% of the VIP populations, respectively. The axons of vertically oriented bipolars were observed to ramify within a column around the descending dendrite. By contrast, multipolar cells have a non-oriented ramification pattern. The two overlapping axonal systems form the VIP-innervation of the rat visual cortex.

Animals↗
PubMed1990

Neural systems contributing to acetylcholinesterase histochemical staining in primary visual cortex of the adult rat.

Histochemical studies demonstrate that cortical area 17 (primary visual cortex) of the adult rat displays a characteristic laminar pattern of acetylcholinesterase (AChE) activity. While AChE-positive axons are found throughout the cortical layers, most intense staining occurs in a band that corresponds to layer V and the deep portion of layer IV. The present studies were directed toward determining the neural systems containing this AChE activity. Unilateral electrolytic or excitatory amino acid induced lesions of the basal forebrain result in reductions of AChE staining in ipsilateral visual cortex, particularly in layers IV and V. Electrolytic or scalpel lesions, placed in white matter underlying dorsal and lateral neocortex to interrupt basal forebrain projections to visual cortex, also reduce AChE staining in visual cortex. Lesions in the cingulate bundle and supracallosal stria reduced AChE staining retrosplenial cortex but did not affect staining visual cortex. Placement of electrolytic lesions in the hypothalamus produced no detectable change in the pattern of AChE in visual cortex. Electrolytic lesions in the midbrain tegmentum, placed to interrupt ascending axons from brainstem monoamine neurons, produced no detectable change in the pattern of AChE in visual cortex. Placement of lesions in the dorsal thalamus that include all of the dorsal lateral geniculate nucleus did not alter AChE staining in visual cortex. The results indicate that AChE activity in adult visual cortex is found primarily within afferent axons from the basal forebrain system. These data demonstrate further that the AChE staining characteristic of adult visual cortex is associated with neural systems that are distinctly different from those associated with AChE staining in visual cortex of the infant rat.

Acetylcholinesterase↗
PubMed1979

A comparison of the organization of the projections of the dorsal lateral geniculate nucleus, the inferior pulvinar and adjacent lateral pulvinar to primary visual cortex (area 17) in the macaque monkey.

Both anterograde and retrograde transport tracing methods were used to study the organization of the projections of the dorsal lateral geniculate (DLG), the inferior pulvinar and subdivisions of the lateral pulvinar to primary visual cortex (striate cortex or area 17). The DLG projects only to striate cortex. These projections are retinotopically organized, and do not extend to any cortical layers above layer IVA. In contrast the inferior pulvinar (PI) and the immediately adjacent portion of the lateral pulvinar (PL alpha 48) project to both striate and prestriate cortex. The projections from these two thalamic areas to the striate cortex are also retinotopically organized and exist in parallel with those from the DLG. In contrast to the DLG, the projections from PI and PL alpha terminate above layer IVA in striate cortex, i.e. layers I, II and III. In prestriate cortex the layers of termination include layers IV, III and I. The pulvinar terminations in layers II and III of area 17 occur in segregated patches as do the geniculate terminations in layers IVC and IVA. On the other hand the pulvinar terminations in layer I which overlie those in layers II and III of area 17 appeared to be continuous. Control studies show that the remainder of the lateral pulvinar overlying PL alpha does not project to striate cortex. It is concluded that there are 3 visuotopically organized inputs from the lateral thalamus to primary visual cortex and that each of these inputs have different layers of termination. The inputs from PI and DLG can convey direct retinal inputs while those from PI and PL alpha can also be involved in intrinsic cortico-thalamocortical connection with prestriate cortex. It remains, then that it cannot be tacitly assumed that the ascending inputs which influence the response properties of the primary cortical neurons arise solely from the dorsal lateral geniculate nucleus. It is also argued that these inputs to the supragranular layers may be excitatory as those from the DLG to the IVth layer.

Animals↗
PubMed1985

Neurogenesis of the cat's primary visual cortex.

The 3H-thymidine method of birth-dating was used to determine when the cells belonging to each of the principal cellular layers of the cat's primary visual cortex are generated. In order to detect systematic differences in the position of radioactively labeled cells following 3H-thymidine administration at different prenatal ages, a geometric method was devised to represent the distribution of labeled cells in the form of depth histograms. Results show that visual cortical neurogenesis occurs largely during the second half of gestation between embryonic day 31 (E31) and E57. Cells of layer 6 are generated early, between E31 and E38, whereas cells destined for successively more superficial layers are generated at progressively later times. Layer 4 cells, the principal targets of geniculocortical afferents, are generated between E37 and E44. In addition, a special population of cells embedded in the white matter below layer 6 was found to be produced throughout the week-long period immediately prior to the onset of layer 6 neurogenesis. Overall, this radial pattern of cortical neurogenesis closely resembles the inside-first, outside-last, spatiotemporal sequence of development described for the monkey's primary visual cortex (Rakic, '74). In addition to finding this pronounced gradient in the radial dimension, we were also able to detect a less pronounced gradient along the tangential dimension: neurons destined for any given layer in the anterior part of the cortex (inferior visual field representation) are generated slightly in advance of neurons destined for more posterior regions (superior visual field). However even our more quantitative histogram analysis failed to reveal a mediolateral (central to peripheral visual field) gradient within area 17. In the cat, layers 6, 5, and 4 each take about a week to be generated, although their total cell numbers and packing densities differ in the adult. About 2 weeks are required to produce the cells of layers 2 and 3 combined. Furthermore, we found that neurons belonging to different layers and different morphological classes can be generated simultaneously. This suggests that the identity of a cortical neuron is not solely a function of the time of neurogenesis.

Age Factors↗