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At least 127 records · Page 7Linked to original sources
PubMed1985

Reinstatement of binocular depth perception by amphetamine and visual experience after visual cortex ablation.

In adult cats with bilateral visual cortex ablation the complete deficit in binocular depth perception, as measured on a visual cliff, was reversed by 4 doses of amphetamine. The amphetamine-induced recovery endured after the amphetamine treatment was discontinued. This enduring recovery of function was not obtained if the animals were housed in the dark during drug intoxication. Therefore, both amphetamine intoxication and visual experience are simultaneously required for recovery of binocular depth perception after visual cortex ablation.

Animals↗
PubMed1986

Cortical activity blockade prevents ocular dominance plasticity in the kitten visual cortex.

Recordings from single units in kitten primary visual cortex show that a reversible blockade of the discharge activities of cortical neurons and geniculocortical afferent terminals by intracortical infusion of the sodium channel blocker tetrodotoxin (TTX) completely prevented the ocular dominance shift that would normally be seen after monocular deprivation. The blockade of cortical plasticity, like the blockade of discharge activity, was reversible, and plasticity was restored following recovery from the effects of TTX. These results extend previous work suggesting involvement of electrical activity at the level of the cortex in the phenomenon of cortical plasticity by demonstrating an absolute requirement for discharge activities in the primary visual cortex.

Action Potentials↗
PubMed1992

Effect of dark rearing on the volume of visual cortex (areas 17 and 18) and number of visual cortical cells in young kittens.

The surface area, total volume, and total number of neurons of areas 17 and 18 in one hemisphere of dark-reared (DR), dark-reared and light-exposed (DRL), and normally reared (NR) kittens were studied at the age of 6 weeks. The thickness of the visual cortex was lower by 13% and 11% (area 17) and by 17% and 16% (area 18) in DR and DRL groups, respectively, when compared with similar cortical areas in NR kittens. The surface area values of area 17 were nearly the same in DR and DRL kittens, both being, however, 37% smaller than in NR animals. The surface area of area 18 was significantly smaller than that of area 17 in each group, and was also lower in DR (by 27%) and DRL (by 21%) groups when compared with the NR group. As a consequence of dark rearing, the numerical density of cortical neurons in area 17 amounted to about double of the value observed in normally reared kittens and was also significantly higher in area 18. The numerical density of nerve cells of DRL kittens fell between the DR and NR groups. The total cortical volume of area 17 was similar in DR and DRL groups but it was by 46% (DR) and by 44% (DRL) smaller than in NR kittens. In each experimental group, the total volume of area 18 was significantly smaller than that of area 17. The cortical volume of area 18 was also smaller than in the NR group by 39% and 34% in DR and DRL groups, respectively. In DR and NR kittens, the total numbers of neurons in areas 17 (DR = 26.4 million, NR = 25.7 million) and 18 (DR = 8.5 million, NR = 9.0 million) were essentially similar. In the DRL groups a significantly smaller number of cortical neurons was found both in area 17 (21.5 million) and in area 18 (6.8 million). It is concluded that, in spite of considerable differences in the cortical thickness, surface area, numerical density, and total cortical volume, the absolute numbers of neurons in area 17 and 18 of visually deprived (DR) and NR kittens do not differ at 6 weeks of age. The main deficit in cortical organization following dark rearing, therefore, appears to be confined mainly to the neuropil, as a result of an underdevelopment of neuronal processes and of depressed synaptic organization.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Why spatial frequency processing in the visual cortex?

The nature of redundancy in visual images is discussed and the methods of removing statistical redundancies are considered. It is demonstrated that local spatial frequency analysis is a highly successful method and it is thus argued that this determines the choice of representation of the visual image by the simple cells of the visual cortex.

Humans↗
PubMed1975

Laminar thermocoagulation of the visual cortex in the rat. II. Visual pattern discrimination.

Hooded rats were trained on a series of four visual discrimination tasks in a Y-maze, and subjected to a variety of posterior cortical lesions. In 17 animals this consisted of an extensive aspiration lesion contralateral to a more superficial lesion made by laminar thermocoagulation and centered over the striate area. After operation the animals were tested on the same problem series. The behavioral deficit in this group varied with the extent and depth of the thermal lesion, and six animals with very superficial thermal lesions displayed an isolated difficulty in solving an encircled triangle problem. This deficit seemed to be referable to widespread involvement of supragranular cortex, and specifically of layer I of area striata which receives an input from the nonspecific thalamocortical afferents. The possible influence of various interlaminar projections upon underlying vertically-oriented cell columns as a mechanism for the mediation of 'selective attention' was discussed.

Animals↗
PubMed1989

Effect of electrical stimulation of locus coeruleus on the activity of neurons in the cat visual cortex.

1. We studied the effect of electrically stimulating the locus coeruleus (LC) and iontophoresing noradrenergic antagonists on visual responses and spontaneous activity of individual cells in the cat primary visual cortex. 2. A bilateral projection from LC to visual cortex was demonstrated anatomically, by retrograde labeling using horseradish peroxidase. Where electrical stimulation of both ipsilateral and contralateral LC affected a cortical neuron, the effect induced by stimulating each side was similar. 3. One hundred and two cells were recorded in area 17: 52% of them had their activity suppressed and 36% had their activity facilitated by LC stimulation. The suppressive effect was predominant in cortical layers II + III and IV, whereas most cells in layer V and one-half of the cells in layer VI were facilitated by LC stimulation. This suggests that LC neurons innervate each cortical layer in a different manner. 4. Simple and complex cells were equally sensitive to LC stimulation. For simple cells, the suppressive effect of LC stimulation was dominant throughout all layers. For complex cells, the suppressive effect was dominant in layers II + III and IV, whereas the facilitatory effect was dominant in layers V and VI. 5. The suppressive effect of LC stimulation was blocked by iontophoretic application of beta-adrenergic receptor antagonists and the facilitatory effect was blocked by either alpha- or beta-adrenergic receptor antagonists. 6. Nonselective alpha-, and selective alpha 1- and alpha 2-receptor antagonists suppressed visual and spontaneous activity in almost all neurons tested, suggesting that these receptors are either facilitatory at a postsynaptic site or inhibitory at a site presynaptic to an inhibitory synapse in the visual cortex. 7. beta-Receptor antagonists facilitated activity in 45% and suppressed activity in 36% of the cells tested, suggesting there are both suppressive and facilitatory types of beta-receptors. 8. The effectiveness of alpha- and beta-antagonists on the activity of neurons without LC stimulation also suggested that spontaneously released noradrenaline activated noradrenergic receptors in the visual cortex even in the anesthetized and paralyzed cat. 9. In most cells tested, both alpha- and beta-receptor antagonists exerted effects on single neurons suggesting that endogenous noradrenaline acts on both alpha- and beta-receptors on the same cell. 10. The activation of LC did not improve the signal- (visual response)to-noise (spontaneous discharge) ratio of neurons in the visual cortex. 11. LC seemed to control the activity of each cortical layer differently, by activating different kinds of noradrenergic receptors in different layers.

Adrenergic alpha-Antagonists↗
PubMed1992

Changes of drebrin expression in the visual cortex of the cat during development.

The expression of and developmental changes in drebrin were studied in cat visual cortex using immunohistochemistry and immunoblot analysis. Drebrin is a developmentally regulated brain protein which in the chicken has characteristic changes in expression related to developmental stage. A monoclonal antibody (MAb M2F6) raised against drebrin, was found to label the neuropil of the kitten visual cortex in the early postnatal period. At 1-3 weeks of age, the staining was prominent in layer IV of the visual cortex. The immunoreactivity, however, was found to be dramatically decreased around the end of the sensitive period for ocular dominance plasticity (approximately 3 months of age). In the adult visual cortex, almost no immunostaining was observed. These developmental changes revealed by an immunohistochemical method were confirmed using immunoblot analysis. Upon immunoblot analysis after SDS-PAGE of protein from the kitten visual cortex, MAb M2F6 was found to recognize two protein bands with molecular weights of 130 kDa (drebrin E) and 140 kDa (drebrin A). The developmental profile of the intensity of the two bands of the drebin closely parallels in time the postnatal changes in cortical susceptibility to visual deprivation. These results indicate that the expression of drebrin in kitten visual cortex is restricted to the early postnatal period and suggest that it may play an important role in the experience-dependent modification of cortical circuitry during the sensitive period.

Aging↗
PubMed1990

Distribution of parvalbumin immunoreactivity in the visual cortex of Old World monkeys and humans.

The macaque visual system has been frequently used as a model for understanding functional aspects of human vision. There are, however, few studies directly comparing biochemically defined neuronal populations in the visual cortex of the two species. In this study we compared the distribution and morphological features of the parvalbumin-immunoreactive neuronal subpopulation within humans and Old World monkeys (Macaca fascicularis and Macaca mulatta) by using monoclonal antibodies against the Ca2(+)-binding protein parvalbumin (PV), a neuronal marker in the vertebrate cerebral cortex. Characteristic laminar density and distribution of PV is observed, matching that seen with cytochrome C-oxidase and gamma-aminobutyric acid (GABA) immunoreactivity. Thus, parvalbumin is prominent in the layers receiving afferents from the dorsal lateral geniculate nucleus. Terminal fields are rich in layer IVA and IVC and moderate in the blob-region of layer II-III of the monkey cortex. In the human visual cortex only layer IVC displays rich terminal fields. Parvalbumin is present in neurons within all layers of the cortex except layer I. Parvalbumin-immunoreactive (PV-ir) axons occur in different lamellae of the white matter containing axons belonging to association or projection neurons. The estimation of PV-ir neurons, determined for 50 microns-wide columns through the thickness of area 17, shows that the percentage of the total neuron number in area 17 of humans containing PV is 6.8 +/- 2.0%, and in the macaque monkey, 11.5 +/- 2.9%. The perikaryal area of PV-ir neurons varies according to the layer and is comparable in humans (109.3 +/- 40.8 microns2) and monkeys (94.3 +/- 29.5 microns2). However, the relative number of large PV-ir neurons is higher in humans. The immunoreactive product fills the thinnest cell processes and the shape of PV-ir neurons can be easily traced with the aid of a camera lucida. The shape of the neurons is similar in the two species studied, and they probably belong to non-spiny stellate, double-bouquet, chandelier, and basket cell classes. This study shows that parvalbumin acts as a marker for a subpopulation of interneurons in area 17, but it is also present in the geniculocortical as well as in corticocortical pathways. Moreover, the Old World monkey and human visual cortices have a similar, but not identical, distribution of this important calcium-binding protein.

Animals↗
PubMedDate not supplied

[Neuronal specialization of the motor cortex in normal rabbits and following destruction of the visual cortex].

The activity of neurones of the anterolateral part of the motor cortex in food-acquisition behaviour was compared in two control rabbits and in three rabbits after the operation of bilateral ablation of the striatal cortex. In two of three operated rabbits the pattern of behavioural specialization lost considerably the specificity peculiar to the motor cortex (predominance of G-neurones activated in grasping of food), approaching (but not becoming identical) the pattern of specialization of the visual cortex neurones: the number of G-neurones decreased in a half, and the number of L-neurones (activated in connection with the acts of instrumental food-acquisition behaviour which animals were trained to in the experimental cage) was doubled. Changes of the activity were significantly less expressed in the third operated rabbit. The number of the neurones activated in food-acquisition behaviour in operated rabbits in comparison with the control ones was reduced in the upper layers of the cortex and increased in the lower layers. The resemblance is discussed of the basic processes of animals learning and behaviour recovery.

Animals↗
PubMed1992

Transcallosally evoked responses in the visual cortex of normal and monocularly enucleated rabbits.

In visual cortex of normal adult rabbits, callosal projections are restricted to a 2 mm wide band at the area 17/18 border. In adult rabbits which are monocularly enucleated (ME) on the day of birth, the callosal zone extends 4 mm into the medial region of area 17 in the cortex ipsilateral to the remaining eye. In this study, the function of these anomalous callosal projections in ME rabbits was investigated using electrophysiological techniques. A microelectrode was placed in the visual cortex ipsilateral to the enucleated eye at the 17/18 border, bipolar stimulating electrodes were placed in a homotopic location in the contralateral cortex, and averaged evoked responses (AERs) to stimulation were recorded. The stimulating electrodes were then moved mediolaterally in 1 mm steps, and the AERs were recorded for each location of the stimulating electrodes. In the normal rabbit, a maximal short latency evoked response was recorded when the stimulating electrodes were at a location homotopic to the recording electrode. When the stimulating electrodes were moved a distance of 1 mm or more from this optimal position, this short latency response was either absent or dramatically decreased in amplitude, reflecting the precise topographic pattern of the normal callosal projection. In contrast, in ME rabbits, a consistent response was evoked at the 17/18 border when the stimulating electrodes were moved as much as 3 mm medial to the homotopic position. Since antidromically activated responses and both pre- and postsynaptic orthodromically activated responses contribute to the AER, recordings were also made from single cells in some animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Transition from developing to mature patterns of acetylcholinesterase activity in rat visual cortex: implications for the time-course of geniculocortical development.

Patterns of acetylcholinesterase (AChE) histochemical staining in cortical area 17 differ in infant and mature rats. In infants, intense AChE activity is seen as a band corresponding to layer IV and deep layer III of the visual cortex, and this staining is associated with terminal fields of geniculocortical neurons. In adult animals, AChE activity is densest in deep layer IV and layer V and is associated with projections originating in the basal forebrain. The present study investigated the transition from developing to mature patterns of AChE staining in visual cortex. Unilateral lesions were placed in either the lateral geniculate body or the basal forebrain of rats postnatal days 8 (P8) to adulthood; the effects of these lesions on patterns of AChE activity in visual cortex were studied with histochemical techniques and optical densitometry. Lesions involving the lateral geniculate body markedly reduce AChE activity in visual cortex of P12 rats, had moderate effects in P20 rats, and had no apparent effect on AChE activity of visual cortex of rats aged P40 and older. Lesions of basal forebrain had little effect on AChE activity in visual cortex of P12 animals, increasing effect in P15-35 rats, and eliminated much of AChE staining in visual cortex of adults. The period of transition from developing to mature patterns of AChE activity in visual cortex of animals bilaterally enucleated at birth was not different from the period of transition in normally sighted animals. These data indicate that mature patterns of AChE activity in visual cortex are not achieved until well into the second month of life. If transient AChE expression is characteristic of geniculocortical neurons during the period of time in which axons are proliferating within visual cortex, then these data indicate that geniculocortical connections may be forming well into the second month of life in the rat.

Acetylcholinesterase↗
PubMed1990

The distribution of M1 and M2 muscarinic acetylcholine receptor subtypes in the developing cat visual cortex.

The binding site characteristics and ontogenesis of [3H]pirenzepine ([3H]PZ) (M1 receptor) and [3H]oxotremorine-M ([3H]OXO-M) (M2 receptor) binding sites were investigated in the cat visual cortex. Scatchard analysis of [3H]PZ binding in adult cat visual cortex revealed a single site with a Kd of 17.3 nm and a Bmax of 352.45 fmol/mg protein. [3H]OXO-M also bound to a single site with a Kd of 7.1 nM and a Bmax of 256.39 fmol/mg protein. Receptor autoradiography revealed that [3H]PZ binding sites were present only in telencephalic structures while [3H]OXO-M sites were distributed heterogeneously throughout the brain. [3H]PZ binding sites in adult visual cortex were present in the superficial and deep cortical layers with the densest labeling in layer I and a distinct band in layer V. [3H]OXO-M sites also avoided the middle cortical layers, but were most prominent in layers V and VI with less pronounced binding in layers I and II. Deafferentation of extrinsic inputs to the visual cortex did not reduce [3H]PZ nor [3H]OZO-M binding, but neuron-specific excitotoxic lesions of visual cortex abolished both populations of binding sites. This indicates that both populations of binding sites are located on cells intrinsic to the cortex. In early postnatal life, both [3H]PZ and [3H]OXO-M binding sites were localized to intermediate cortical layers. Following this, the laminar distribution of both populations redistributed; each with its own idiosyncratic profile. By postnatal day 49, [3H]PZ binding sites redistributed into the superficial and deep layers, the pattern of adult animals, while [3H]OXO-M sites maintained a pattern similar to younger animals, with substantial binding persisting in layer IV. As late as postnatal day 70, well after [3H]PZ binding sites had achieved their mature laminar pattern, [3H]OXO-M binding sites in visual cortex had not achieved their characteristic adult pattern. In addition, the normal laminar redistribution of both [3H]PZ and [3H]OXO-M binding sites during postnatal development of the cat visual cortex was prevented by eliminating cortical afferents in early postnatal life. This indicates that muscarinic receptor rearrangement in development is dependent upon cortical input or output.

Animals↗
PubMed1977

Direct projections from thalamic intralaminar nuclei to extra-striate visual cortex in the cat traced with horseradish peroxidase.

Thalamic projections to the visual cortex were investigated using the Horseradish peroxidase tracing technique. Besides confirmation of a distinct origin of thalamic projections to striate and extra-striate visual cortex, afferents of the intralaminar nuclei (ILN) to visual cortex were demonstrated. These projections of ILN were shown to be specific in that they terminate in areas 18, 19 and Clare Bishop but not area 17. The coupling of these intralaminar projections on to the extra-striate visual system is considered with respect ot orientation of gaze.

Animals↗
PubMed1988

Genesis of GABA-immunoreactive neurons in the ferret visual cortex.

The pattern of neurogenesis of GABA-immunoreactive neurons in the ferret primary visual cortex was determined using immunohistochemical and 3H-thymidine autoradiographic techniques. Neurons in the visual cortex of the ferret undergo their final cell division during a period extending from embryonic day 20 (E20) to postnatal day 14 (P14) and follow an inside-out pattern of neuronal production (Jackson et al., 1984) similar to that observed in other mammals. Earlier-generated neurons are found at deeper cortical positions in the adult than are those generated later. Layer I is an exception to this rule, since neurons destined for this layer are produced at both the beginning and end of neurogenesis. In this study, the pattern of neurogenesis of GABA-immunoreactive neurons is compared to the pattern observed for nonimmunoreactive neurons. The overall pattern of cortical neurogenesis (inside-out pattern) is similar for GABA-immunoreactive neurons and neurons that are not GABA-immunoreactive. However, the GABA-immunoreactive neurons born on a given day of development are more broadly distributed across the radial axis of the adult cortex than are nonimmunoreactive neurons generated on the same day. GABA-immunoreactive neurons generated later in neurogenesis are, on average, slightly smaller than those generated early. If GABA-immunoreactive neurons in the visual cortex are interneurons, then these findings suggest that interneurons follow the same pattern of neurogenesis as do projecting neurons in the visual cortex.

Animals↗
PubMed1988

Naso-temporal asymmetry of visual perception and of the visual cortex.

The decrease of visual performance from the fovea towards the periphery depends upon the task tested. The slope of the decrease is generally steeper for hyperacuity than for spatial resolution and is steeper in the nasal than in the temporal hemifield. The naso-temporal asymmetry in the periphery of the visual field, beyond 20 deg eccentricity, is much more pronounced for hyperacuity than for spatial resolution. The psychophysical results show a close correlation to the cortical organization as revealed by autoradiography.

Adult↗
PubMed1975

[Interhemispheric relations of the cat visual cortex following unilateral polarization of the secondary visual area].

In 40 anesthetized cats, evoked potentials following light flashes during unilateral polarization of the secondary cortical visual area with DC anode (2-10 mcA) were studied in symmetrical centers of the 17th and 18th fields. Four phases of interhemisphere interrelationships between the 18th field's symmetrical centers were shown: 1 -- extracallosal phase of synergic depression; 2 -- callosal phase of dominant interrelationships; 3 -- callosal phase of synergic depression; 4 -- callosal-extracallosal phase of dominant interrelationships. In symmetrical centers of the 17th field, the only 1 extracallosal phase of synergic depression was observed during which the transcallosal modulation of nervous processes occurred. The data obtained are interpreted from the standpoint of the role of dominanta in interhemisphere interrelationships.

Animals↗
PubMed1989

Noradrenergic control of ocular dominance plasticity in the visual cortex of dark-reared cats.

In the visual cortex of cats which had been dark-reared for several months since the time before natural eye opening, a cortical infusion of 6-hydroxydopamine (6-OHDA), a noradrenaline (NA)-related neurotoxin, partially suppressed a usual shift in ocular dominance following brief monocular lid suture, causing a significant loss of binocular cells. This partial shift in ocular dominance (U-shaped histogram) was also observed typically in the control hemisphere of cats which were subjected to dark-rearing for more than a year. Furthermore, the expected shift in ocular dominance following monocular deprivation was blocked by a direct cortical infusion of D,L-metoprolol, a selective beta 1-adrenergic receptor antagonist. The blockade was not obtained by D-metoprolol, a biologically inert stereo-isomer, under the comparable condition. In contrast, exogenous L-NA gave rise to an obvious shift in ocular dominance toward the non-deprived eye. The present results suggest that the NA-beta 1 adrenoreceptor system was necessary to maintain the ocular dominance plasticity in the visual cortex of dark-reared cats.

Animals↗
PubMed1985

Plasticity in cat visual cortex restored by electrical stimulation of the locus coeruleus.

It has been proposed that the presence of noradrenaline (NA)-containing terminals and NA-related receptors within the visual cortex is necessary to maintain the high level of neuronal plasticity in the immature visual cortex of kittens. In the present study we wanted to show whether electrical stimulation of the locus coeruleus (LC), which contains the somata of these cortical NA fibers, can restore neuronal plasticity to the normally aplastic visual cortex of juvenile and adult cats. We consistently found a significant loss of binocular cells in the visual cortex of mature animals which had monocular vision for only 12 h dispersed over 6 days (2 h a day, otherwise kept in the dark) in combination with concurrent LC stimulation. This result was interpreted as indicating that endogenous NA released from NA terminals restored susceptibility to monocular vision in the mature visual cortex. We next examined how long the restored plasticity lasts in the same animals after the LC stimulation was ended. The animals revived from the first recording session were either returned to the same daily schedule of brief monocular exposure (light/dark = 2/22 h) as before, or subjected to the usual monocular lid suture and kept in a cat colony environment (light/dark = 16/8 h). The LC electrodes had been removed and no more electrical stimulation was delivered at this stage. In the animals subjected to reiteration of brief monocular exposure, the state of reduced binocularity gradually returned to normal over a period of 2-3 weeks after stopping LC stimulation. We calculated that the revived plasticity disappeared at an average rate of a 22% loss every 7 days. This result sharply contrasted with the result obtained in the animals subjected to usual monocular lid suture. In this test the state of reduced binocularity continued for at least the next 3 weeks, suggesting that the restored plasticity was sustained throughout a period of 3 weeks (longest term tested). The different results obtained in the two paradigms may be explained by the different strength of binocular imbalance in the two tests imposed on the visual cortex in which neuronal plasticity was restored partially.

Animals↗