[Development of Meynert cells in cat visual cortex under the conditions of flickering light stimulation].

To examine the effect of rhythmical light stimulation on postnatal development of the visual system, the formation of Meynert cells was studied in area 17 and posteromedial suprasylvian area (PMLS) of kittens reared under the conditions of flickering light stimulation (15 Hz frequency). Profile area of neuronal cell bodies and cytochrome oxidase (CO) activity level were measured in frontal sections of the visual cortex in control (n = 6) and stimulated (n = 6) kittens. Meynert cells located in area 17 and PMLS demonstrated an approximately 37% increase in CO activity in the stimulated animals. At the same time, the profile area of Meynert cell bodies in PMLS was decreased by 20% as compared to that in normal animals. The presence of functional disturbances of Y-conducting visual channel and the possibility of binocular vision suppression in the stimulated animals are discussed.

[Retinotopic organization of the lateral suprasylvian sulcus' posterior-medial area as revealed by analysis of the pattern of cortico-cortical connection with the cat 17th area].

Using cortico-cortical connection analysis technique, the cat visual area PMLS (the area located on posterior medial wall of the lateral suprasylvian sulcus) retinotopic organization was investigated. A retrograde axonal tracer: horseradish peroxidase (HRP), was injected in the PMLS, and initial neurons were investigated in area 17. It was shown that after HRP injection in PMLS locus, where a central vision field is located, a labelled cell pattern in area 17 corresponded to the L. Palmer et al., 1978, retinotopic map. On the contrary, after HRP injection in PMLS locus, where an upper vision field must be located, as L. Palmer et al., 1978 predicted, initial neurons are visualized in area 17 loci where low visual periphery is displayed: -10 degrees to -60 degrees in vertical meridian and 40 degrees to 80 degrees in horizontal meridian. Such discrepancy in upper and lower visual field representation was also obtained in electrophysiological and topographic investigations by Grant, Shipp, 1991. The data suggest necessity of S. Grant and S. Shipp's retinotopic map use in the cat area PMLS morphofunctional investigation.

[Development of primary visual cortex connections with the motion processing center: the role of visual environment].

Development of axonal connections between cat primary visual area 17 and visual motion processing center was studied to investigate cortico-cortical connection plasticity in ontogenesis as affected by an experimental modification of visual environment (flickering light stimulation). By using a retrograde axonal labeling by horseradish peroxidase, a distribution of initial neurons in area 17 that send afferent projections to PMLS (posterior medial part of lateral suprasylvian sulcus) was analyzed. Sixteen 5-week-old and 12-14-week-old kittens, than were reared in normal visual environment or were subjected to a flickering light of 15 Hz frequency, were examined. It was shown that session stimulation by flickering light led to an impairment of normal development of regular organization of the connections between these visual areas including the decrease of labeled surface area and labeled initial neuron density in area 17. The data obtained elucidate the structural bases of cortical mechanisms that underlie motion processing disturbances in kittens stimulated by a flickering light.

[Ontogenetic specifics of organisation of the cortico-cortical connections of the cat primary visual cortex and lateral suprasylvian area].

A quantitative and qualitative analysis of distribution of initial cells that organize the cortico-cortical connections between area 17 and posterior-medial lateral suprasylvian area (PMLS) was carried out in 10 kittens (5- and 12-week old). A horseradish peroxidase labeling technique was used. PMLS area is the highest center of moving visual stimuli information processing. Certain ontogenetic peculiarities of the area 17 initial neurons regular (clustered) organization were revealed. An age-related decreasing of the area 17 initial neurons packing density was shown (from 125.19 +/- 69.75 cells/mm2, in 5-week kittens to 34.67 +/- 17.38 cells/mm2--in 12-week kittens (p = 0.05)). It was shown also that an increasing of striate cortex locus that contained a gross majority of marked neurons occurs from 5-th to 12-th postnatal week. Possible morpho-functional aspects of ontogenetic formation of connections between area 17 and area PMLS clustered structure and its possible relation to development of visual moving stimuli perception are discussed.

[Early ontogenetic development of regular organization of corticocortical connections between visual areas 17 and posteromedial lateral suprasylvian area in the cat].

Early ontogenetic development of cluster organization of corticocortical connections between visual areas 17 and posteromedial lateral suprasylvian area (PMLS) was studied in cat. Retrograde axonal tracer horseradish peroxidase was microinjected into the area PMLS. Labeled initial neuron distribution was analyzed in area 17 in 5- and 12-week-old kittens. A significant increase of the cortical surface area containing labeled neurons together with the decrease in their distribution density were shown between weeks 5 and 12. An analysis of amplitude and phase of Fourier spectra of labeled neuron distribution patterns demonstrated some differences between the kittens of various age groups and indicated the incompleteness of connection cluster organization formation. The temporal morpho-functional features of the development of PMLS zone corticocortical connections, as compared to the other visual cortical areas, are discussed.

[ A method for detection and quantitative analysis of two-dimensional patterns of labeled neuron distribution in the cerebral cortex].

The aim of the present investigation was to elaborate an algorithm for labeled neuron 2-D pattern reconstruction and its analysis. Using the study of cat cortico-cortical connections between the areas 17, 18 and posteromedial lateral suprasylvian area as an example, it was shown that proposed algorithm is adequate for present aims of initial neuron pattern reconstruction and analysis, and that it can be applied as a working algorithm for highly specialized computer program elaboration.

Effects of amplitude-frequency characteristics of a noise-masked test stimulus on the shapes of visual evoked potentials.

Visual evoked potentials produced in response to a reversive checkerboard pattern presented in conditions of additive noise were recorded. Changes induced by noise in both the shapes of evoked potentials and the structure of the test stimulus were compared. The nature of changes in the shapes of evoked potentials was found to correlate with the nature of changes in the amplitude-frequency spectrum of the stimulus. These results support the gestalt psychology point of view that the visual system uses spatial frequency rather than discrete means for describing information.

Effects of transient and prolonged flashing light stimulation on the cytochrome oxidase module system in layer IV of the primary visual cortex of kittens.

Cytochrome oxidase spots in layer IV of field 17 of the primary visual cortex were studied in kittens aged 33, 49, and 93 days, stimulated with a light flashing at a frequency of 15 Hz. The kittens of one group received stimulation from the moment of eye opening until euthanasia (prolonged stimulation); other groups received stimulation for eight days starting from ages 26, 42, or 85 days (transient stimulation), again until euthanasia. Both types of stimulation were found not to alter the geometrical characteristics of cytochrome oxidase spots, but led to significant increases in the contrast of spots located in the splenial gyrus. Increases in spot contrast in the lateral gyrus occurred only after prolonged stimulation to age 93 days or after transient stimulation from age 26 days to age 33 days. Thus, stimulation of kittens of different ages with a light flashing at a frequency of 15 Hz led to structural-metabolic changes in the primary visual cortex. These changes were apparent to different extents in areas of the cortex responsible for central and peripheral vision. This may be explained, firstly, by the predominant activation of the Y conducting channel of the visual system and, secondly, by the increase in dominance of the contralateral input to the primary visual cortex.

[The effect of amplitude-frequency characteristics of the noise-covered test stimulus on the form of visual evoked potentials].

Visual evoked potentials in response to reverse checkerboard patterns presented in additive noise were analyzed. An induced by noise changes in visual evoked potentials form and in amplitude-frequency spectrum of checkerboard patterns were compared. It was found that character of visual evoked potentials form alteration correlated with stimulus amplitude-frequency spectrum alterations. Results obtained here support Gestalt-psychology view about using by visual system a spatial-frequency but not a discrete information description.

Some aspects of the modular organization of the primary visual cortex of the cat: patterns of cytochrome oxidase activity.

The distribution of the enzyme cytochrome oxidase (CO) in continuous series of parasagittal sections from field 17 and frontal sections of the dorsal nucleus of the lateral geniculate body (LGB) from normal kittens and adult cats was studied. In all cats apart from neonates, layer IV showed regularly alternating areas with above-background levels of CO activity ("spots"). There was a significant increase in the contrast of the "spots" from days 13 to 21, which was followed by a significant decrease from days 48 to 93. These changes coincided with ontogenetic changes in the level of visual system plasticity. There were no differences in CO activity between layers A and A1 of the dorsal nucleus of the LGB. It is suggested that the non-uniform distribution of the level of functional activity of neurons in field 17 reflects the formation of columnar cortical structures during the critical period of postnatal ontogenesis.

[Effects of short-term and prolonged flickering on the system of cytochromeoxidase modules of the kitten primary visual cortex IV layer].

CO "spots" in layer IV of primary visual cortex were investigated in 33, 49 and 93-days kittens that were subjected to flickering light stimulation. Kittens from first group were stimulated since eye opening (long-term stimulation), other kittens--since postnatal day 26, 42 or 85 until euthanasia (short-term stimulation). Both types of stimulation did not disturb CO "spots" spatial organization but obviously increased a contrast of splenial CO "spots". Lateral "spots" contrast increasing took place after long-term stimulation until the 93rd postnatal day or after short stimulation since 26th to 33rd postnatal day. Flickering light stimulation seems to lead to structural and metabolic alterations in primary visual cortex. These alterations are processed in different way in regions of area 17 that is responsible for central and peripheral vision, respectively. It seems to reflect, firstly, primary activation of Y processing stream and, secondly, the strengthening of contralateral input to area 17.

A periodic pattern in the distribution of cytochrome oxidase activity in the visual cortex in kittens.

The aim of the present work was to study the distribution of cytochrome oxidase activity in the visual cortex of kittens in normal conditions. Studies were performed using computer filtration of digitized images of frontal sections. The occurrence of regularly alternating levels of enzyme activity was demonstrated in layers III, IV, and VI of field 17 and layers IV and VI in field 18.

[Some aspects of modular organization of the cat primary visual cortex: cytochrome oxidase activity pattern].

Distribution of enzyme cytochrome oxidase (CO) activity was studied in a continuous series of parasagittal sections of cortical area 17 and frontal sections of dorsal lateral geniculate nucleus (LGNd) in kittens of different age and adult cats. In all the kittens except the newborns, in layer IV of area 17, regular alternating areas of CO activity, exceeding the background activity ("spots"), were detected. During the period between postnatal days 13 and 21 a significant increase of "spots" contrast took place, while between postnatal days 48 and 93 contrast was significantly decreased. This contrast changes coincided with the dynamics of visual system plasticity during ontogenesis. No differences in CO activity were detected between layers A and A1 in LGNd. It is suggested that non-uniform distribution of functional activity of area 17 neurons reflects the development of cortical columns during the critical period of postnatal ontogenesis.

[Periodical pattern of cytochrome oxidase activity distribution in the visual cortex of kittens].

The aim of this study was to determine the distribution of cytochrome oxidase activity in the visual cortex of normal kittens. Method of computer filtration of digital images of frontal sections was used. The periodicity of enzyme activity in layers III, IV, VI of area 17 and in layers IV, VI of area 18 has been shown.

Characteristics of cytochrome oxidase activity in visual system neurons in kittens reared in conditions of flashing illumination.

The studies reported here addressed the effects of flashing (15 Hz) lights on the metabolic activity of visual system neurons in animals reared in condition of crepuscular illumination. Activity of the respiratory enzyme cytochrome oxidase was detected in the cortex of visual areas 17 and 18 and in the lateral geniculate body in kittens. The results showed that kittens subjected to this stimulation, unlike intact kittens and kittens reared in conditions of crepuscular illumination, showed a change in the pattern of cytochrome oxidase distribution in cortical field 17 consisting of the appearance of alternating areas of increased and decreased enzyme activity in layers III and IV. In cortical field 18 and the lateral geniculate body, experimental kittens showed no changes in the cytochrome oxidase activity distribution pattern. It is suggested that flashing illumination leads to disturbance of the balance in activity in the Y and X conducting channels of the visual system.

[Peculiarities of cytochrome oxidase activity in the visual cortex neurons of kittens reared under the conditions of flickering illumination]. / Osobennosti aktivnosti tsitokhromoksidazy neironov zritel'noi sistemy kotiat, vyrosshikh v usloviiakh mel'kaiushchego osveshcheniia.

The objective of this study was to analyze the influence of the light flickering with the frequency of 15 Hz, on the neuronal metabolic activity in kittens reared under the conditions of mesopic illumination. The method for demonstration of a respiratory enzyme cytochrome oxidase was used to study the visual cortex areas 17 and 18 and the lateral geniculate nucleus. It was shown that in kittens that were subjected to this stimulation as opposed to intact animals and to kittens reared under the conditions of mesopic illumination, specific changes in pattern of cytochrome oxidase distribution in area 17 took place. This change was manifested by the appearance of alternating zones of increased and decreased enzyme activity in layers III and IV. Within the cortical area 18 and lateral geniculate nucleus, no changes in the pattern of cytochrome oxidase activity distribution were detected in experimental kittens. It is suggested that flickering illumination results in disequilibrium of Y- and X-visual pathway activity.