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M Kossut

Publications and source records attributed to M Kossut.

69 records · Page 4Linked to original sources
PubMed1984

Crosscorrelation analysis of intracolumnar neuronal connectivity in area 17 of binocularly deprived cats.

Eight cats were binocularly deprived of pattern vision by rearing in masks from the time of eye opening. Twenty five groups of 3 neurons and 28 neuronal pairs were studied in visual orientation columns of their striate cortices. The crosscorrelograms of neuronal discharges were analyzed and the inference of underlying interneuronal connectivity was made. The results were compared with the normal cats data obtained earlier in an identical experiment. Total number of existing interactions was only slightly reduced: from 95010 of analyzed pairs in normal cats to 90 percent in deprived animals. The most pronounced effect of visual deprivation was the reduction of the percentage of neuronal pairs that shared the same source of input from 61 to 34 percent. The proportion of direct excitatory connections was not affected, while an increase in the number of inhibitory correlations was found.

Animals↗
PubMed1983

Development of orientation columns in cat striate cortex revealed by 2-deoxyglucose autoradiography.

In the striate cortex of adult monkeys and cats, both electrophysiology1-3 and the 2-deoxyglucose autoradiographic technique of Sokoloff4-8 suggest that neurones are arranged in functional columns or slabs that run through the full thickness of the cortex, each column containing cells with a preference for a particular orientation of line or edge in the visual field. There is disagreement, however, concerning the organization of visual cortex in very young animals and the role of visual experience in cortical development. Orientation-selective neurones clearly exist in immature cat cortex, but reports differ on their frequency, angular selectivity and degree of columnar organization (see ref. 9 for review). We have used 2-deoxyglucose autoradiography to investigate the development of cat striate cortex. This technique reveals the spatial distribution of activity in populations of neurones and should therefore provide information about how the columnar pattern develops and whether its maturation depends on visual stimulation. We report here that in normal animals, periodic metabolic labelling around layer IV was first clearly observed at 21 days of age and by 35 days the pattern had become truly columnar; in a matched series of animals deprived of normal pattern vision no differential label was observed except for weak periodicity in a single 35-day-old animal. These results suggest that cat striate cortex is immature at the time of eye-opening and that visual experience is crucial for normal maturation.

Age Factors↗
PubMed1983

Responses of area 17 neurons in cats binocularly deprived by rearing in hoods.

Responses of single units of area 17 were recorded in cats binocularly deprived by rearing in hoods. Neurons were recorded in pairs or in three-neuron groups with multichannel microelectrodes. Of 131 units recorded 22 percent were not visually excitable. The rest were predominantly monocularly driven. Response strength defined as the PST peak-to-background ratio was lower than 10 in 90 percent of cells. The orientation selectivity defined as the ratio of response strengths for the preferred and null stimulus orientations was lower than 5 in 79 percent of neurons. Directional selectivity was detected in 22 percent of units. The aim of this paper is to show that, considering the electrophysiological effects in cortica1 area 17, rearing in hoods can be used instead of eyelid suturing. This paper describes the standard parameters of units that were subsequently used for the analysis of interneuronal connectivity in visually deprived cortex (10).

Adaptation, Physiological↗
PubMed1983

Ocular dominance columns in cat striate cortex and effects of monocular deprivation: a 2-deoxyglucose study.

Ocular dominance columns were demonstrated in the visual cortex of kittens by [3H]-2-deoxyglucose autoradiography after monocular stimulation with patterns of different orientations. On horizontal sections through area 17, a pattern of periodic labelling extended throughout the entire thickness of the cortex. Three days of monocular deprivation disrupted that pattern. The ocular dominance columns driven by the deprived eye no longer extended through all cortical layers; only layer IV and immediately adjacent parts of layers III and V showed distinct periodic labelling. After 7 days of eyelid closure periodicity in layer IV was faint, but detectable. Heavy labelling of the lower part of the cortex, observed in normal animals, disappeared during monocular deprivation.

Animals↗
PubMed1981

Dynamic changes of serotonin levels during the first visual experience of binocularly deprived kittens.

Kittens deprived of pattern vision until the 28th day of life received monocular visual experience for 3, 6, 14, and 75 h. Biphasic response of serotonin was found in the visual cortex. Stimulation for 3 h resulted in an increase of serotonin level whereas at 14 h it produced a decrease. The effects are transient, no longer observable after 75 h stimulation. No changes were observed in somatosensory cortex.

Animals↗
PubMed1978

The ocular following reflex in cats deprived of pattern vision from birth.

An investigation of vertical ocular following reflexes evoked from retinal sites of different horizontal eccentricity was carried out on visually deprived cats. The recording was performed in pretrigeminal preparations where horizontal eye movements are absent. A light slit or a black stick (1 degrees X 4 degrees) were moved with 10 degrees/sec speed for 2 sec along the vertical meridian or parallelly up to 40 degrees in the nasal or temporal hemifield. As in previously described normally reared cats, the following reflexes were evoked from the whole area, but the pursuit movements had longer latency and lower velocity at the periphery than in the center of the retina. However, irrespectively of the place of stimulation, the latency of the pursuit movements was longer, their velocity lower and the course less regular than in normally reared cats. It therefore follows that in visually deprived cats the ocular following reflex is impaired.

Age Factors↗
PubMed1978

The effect of first visual stimulation on incorporation of labelled leucine into cerebral cortex of binocularly deprived kittens.

One-month old kittens, binocularly deprived with hoods from birth, were used. Before the experiments in which visual stimulation was applied the brainstem of kittens was transected at the pretrigeminal level. Cortical EEG activity and ocular behavior indicated that the isolated cerebrum of preparations was usually awake during experiment. Patterned visual stimulation was directed to one hemisphere, while the other was used as a control. Visual stimulation evoked in some cases (in 8 out of 17) an increase of incorporation of labeled leucine into the proteins of the striate cortex. Electrophoresis on polyacrylamide gel did not reveal any differences in the pattern of insoluble proteins between the stimulated and control visual cortex. It is suggested that first visual stimulation may enhance the protein metabolism of striate cortex in young kittens. Some unknown up to now physiological factors (motivation, attention?) may be critical for these phenomena.

Animals↗
PubMed1976

Electrophoretic patterns of insoluble proteins in the sensory cerebral cortex of visually deprived and normal kittens.

Insoluble proteins were investigated in the visual cortex (area 17) and somatic sensory cortex of one month old kittens. Visual deprivation did not affect the electrophoretic pattern but changed percentage distribution of proteins in both cortices. Some of the alterations seemed to appear only in the visual cortex, which is morphologically and functionally deficient in deprived kittens. Electrophoretic patterns of normal kittens differed from those of normal adult cats.

Age Factors↗
PubMed1975

Single-unit responses to natural objects in area 19 of cats with different early visual experiences.

Cats deprived of pattern vision with hoods and normal cats were used. During the first 3 months of life some hood-reared cats had visual experience with a three-dimensional cross or a ping-pong ball. Recording were performed in adult cats with a pretrigeminal brainstem transection. Unit responses to the cross and the ball were recorded in area 19 within the projection of area centralis. Stimulus-dominance of the exposed object was manifested weakly. Both exposed and control objects activated more units in the experienced hood-reared cats than in hood-reared and normal controls. Compared with previous finding, the present results indicated that early visual experience affects area 19 differently than areas 17 and 18.

Age Factors↗
PubMedDate not supplied

The distribution of cholinergic muscarinic receptors in the dog frontal lobe.

The topographical distribution of cholinergic muscarinic receptor (MChR) sites was studied by means of quantitative receptor autoradiography using [3H]quinuclidinyl benzilate ([3H]QNB) in the frontal (prefrontal, premotor and motor) cortex of the dog. The mean binding value in the frontal cortex was 408 +/- 5.0 fmol/mg tissue and the only area that differed significantly from the mean was the primary motor cortex, where the binding value was significantly lower. In the dorsal part of the prefrontal and premotor cortical subregions studied, a tri-laminar pattern of [3H]QNB labelling was observed, with a superficial dense band of label corresponding to cortical layers I, II and III. The deep high density band overlaid layer V and the upper part of the layer VI. In the ventral part of the prefrontal cortex this pattern gradually disappeared and in the most ventral part no laminar differences were seen. In contrast, in primary motor areas, the deep band of labelling corresponding to layer V was much less pronounced than in the frontal association cortex. Variations in the distribution of MChR sites seem to reflect to some extent the greater cytoarchitectonic differentiation of the dorsal zone and also the similarity between the ventral zone and the limbic cortex described by us previously.

Animals↗
PubMedDate not supplied

Short-lasting classical conditioning induces reversible changes of representational maps of vibrissae in mouse SI cortex--a 2DG study.

It has been known for several years that receptive field properties of sensory cortical neurons can be altered by learning experiences. We attempted to visualize a global change of the cortical body map induced by learning. In order to do this a short-duration classical conditioning involving stimulation of a row of mystacial vibrissae in mice was followed with 2-deoxyglucose (2DG) mapping of functional activity. Three conditioning sessions that paired stimulation of a row of whiskers with a tail shock produced an increase of the functional representation in somatosensory cortex (SI) of a row of the whiskers stimulated during the training. This plastic change of vibrissal representation in SI was visualized with 2DG autoradiography a day after completion of training. The expansion of representation was the most pronounced in cortical layer IV, and to a lesser extent, in layer IIIb. The expansion was observed in conditioned but not in pseudoconditioned mice or in animals that received only the conditioned stimulus. If training was discontinued, the enlargement of vibrissal representation progressively faded. The reversal could be accelerated by a behavioral extinction procedure. This study gives the pictorial demonstration of rapid, transient, and extinguishable learning-dependent changes in SI cortical maps.

Animals↗
PubMedDate not supplied

Partial blocking of NMDA receptors reduces plastic changes induced by short-lasting classical conditioning in the SI barrel cortex of adult mice.

The effect of blockade of N-methyl-D-aspartate (NMDA) receptors in the barrel cortex upon the learning-induced changes of the cortical body map was examined in adult mice. We have previously found that three sensory conditioning sessions, in which stimulation of a row of vibrissae was paired with a tail shock, produced an enlargement of the functional representation of a row of vibrissae stimulated during training. Implantation of the slow release polymer Elvax, containing 2-amino-5-phosphonovalerate (APV, 50 mM), in the vicinity of the barrel cortex was performed 1 day before conditioning to block NMDA receptors. The cortical representation of a trained row of vibrissae was visualized with 2-deoxyglucose (2DG) functional brain mapping 1 day after the completion of the conditioning procedure. The partial blockade of NMDA receptors within the barrel cortex reduced (by half) the expansion of the cortical representation of a trained row of vibrissae as compared to the enlargement of the cortical representation of a trained row found in untreated (60%) and Elvax-PBS implanted (47%) mice. The results provide evidence that the learning-induced processes of cortical map reorganization involve mechanisms that depend on NMDA receptor activation.

2-Amino-5-phosphonovalerate↗
PubMedDate not supplied

[Brain plasticity].

The ability to undergo lasting changes of neuronal response properties i.e. plasticity, is one of the most important aspects of functioning of the nervous system. The paper reviews the plastic changes of adult mammalian cerebral cortex. It describes compensatory plasticity induced by peripheral denervation and compensatory plasticity following central trauma. Neuronal mechanisms of cortical neuroplastic changes are presented and the common rules of all forms of cortical modifications are discussed. The paper stresses the therapeutic value of training in various sensory modalities for corrections of functional maladaptation of cortical maps and compensation of function after stroke.

Adaptation, Physiological↗
PubMedDate not supplied

[Disorders of the development of perceptual functions in children with epilepsy].

The study was carried out for determination of the profile and for the analysis of disturbances in the development of perceptive functions in children with epilepsy. The psychological-statistical analysis was carried out in 80 children aged 7-14 years. Disturbances of general intellectual development were found in 31 cases (38.75%). Normal intelligence level was demonstrated in 43 children (53.75%), while in 6 cases (7.5%) the intelligence quotient was above normal. Disturbances in the development of visual perception and visuomotor coordination were discovered in 46 children (57.5%). Weakening was observed also of the memory function, mainly recent auditory memory (8.75%) and other partial deficits in the development of higher nervous system functions.

Child↗