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Biomedical subjects

Iu E Shelepin

Publications and source records attributed to Iu E Shelepin.

At least 19 recordsLinked to original sources
PubMed2001

[Visual evoked potentials in response to dichoptic presentation of sinusoidal grating and noise background].

Dichoptic stimulation was used in comparison of visual evoked potentials (VEPs) with those obtained with monocular stimulation (recordings made from the occipital area). 16 subjects viewed sinusoidal gratings with the right eye while a visual noise was added via a mirror for the left eye. In presence of the noise, amplitude of the early VEP components' N1, P1b, and the late component P2 decreased, P1a is not changed in presence of the noise, and the late negative wave N2 increased for all spatial frequencies. The effect of noise on the amplitude of VEPs obtained for monocular and dichoptic stimulation was similar. The data suggest that external noise is filtered by the V1 cortical neurons--matched filters for the gratings.

Adolescent↗
PubMed1995

[The effect of the destruction of the striate and prestriate cortices on the differentiation of visual images in cats].

The experiments to examine the effects of different visual cortical lesions (area 17 and 21 of the cat cortex) on the image discrimination were conducted. Different image complexity and context of images presentation were established. Cats with area 17 lesion easily discriminated simple objects, and learned only positive image from context. Cats with area 21 lesion learned all experimental conditions. We suggest that intact area 21 carry out selection one object context.

Animals↗
PubMed1990

[Assessment of individual eye protection devices based on their effect on the frequency-contrast characteristics of the visual analyzer].

Assessment of means for individual eye protection by the method of visocontrastometry, allows, already at the stage of projecting, to determine the correctness of selecting vision glasses by conditions of visual work. Investigations of 3 kinds of goggles: for reindeer breeders of Far North (2 variants), for mechanics and for protection from pesticides have shown that by their influence on frequency-contrast characteristic all they comply with physiologic hygienic demands. The value of the used method of control of the quality of individual eye protection means is established.

Agricultural Workers' Diseases↗
PubMed1984

[Image discrimination after extirpation of the striatal or the lateral suprasylvian areas of the cerebral cortex in the cat].

Selective lesion of the cat striatal cortex lowered the visual acuity although the figure discrimination only became worse in differentiating among certain shapes differing from each other in their high frequency harmonic components of the image's spatial--frequency range. Lesion of the lateral suprasylvian area leaves the visual acuity intact but disturbs differentiation of all images. The data obtained are compatible with previously stated suggestion that rather local and mainly high--frequency description of images occurs in the striatal cortex whereas a more global and mainly low-frequency one takes place in the lateral suprasylvian area.

Animals↗
PubMed1984

[Correlation of topographic and spatial-frequency characteristics of the lateral suprasylvian region and the striate cortex in the cat].

Modulation transfer functions and retinotopic organization of the two largest areas of visual projections in the cat cerebral cortex were determined and compared. Receptive fields of the neurons in the lateral suprasylvian area are large and their size rapidly increases with eccentricity. In spatial-frequency terms they are low-pass filters. Latent time of visual evoked potentials is shorter in the suprasylvian area than in the striate cortex. It means that low spatial frequencies are transferred more quickly in that area than high spatial frequencies in the striate cortex. Reciprocal connections of the two retinotopically organized areas may accomplish the correlation of high and low frequency descriptions occurring in them.

Animals↗
PubMed1982

[Spatial frequency characteristics of the receptive fields of neurons of the lateral suprasylvian area of the cerebral cortex in the cat].

Two-dimensional spatial-frequency characteristics of the receptive fields of 46 neurons in the lateral suprasylvian area were analyzed in awake cats. Extreme spatial frequencies were disposed in the range less than 1.5 cycle/deg. Spatial-frequency bands were measured for 21 neurons, their mean value was 1.47 +/- 0.5 octaves. 17 neurons had inhibitory characteristics if testing gratings were of nonoptimal orientations. For 6 neurons the inhibitory characteristics measured with nonoptimal orientations were in form of a narrow band with mean value of 1.47 +/- 0.6 octaves.

Animals↗
PubMed1981

[Orientational selectivity and space-frequency characteristics of the receptive fields of occipital cortex neurons in the cat].

Spatial-frequency characteristics and orientation selectivity of the visual cortex neurons are studied in nonanesthetized cats. Gratings presented visually in a preferable orientation and proper spatial frequency evoked the largest responses. All other grating orientations evoked either small excitatory or even inhibitory responses. The largest inhibitory responses were observed when grating orientation was orthogonal to the preferable one. This inhibition depended on the grating spatial frequencies.

Animals↗
PubMed1981

[Relation between the size and eccentricity of the receptive fields of lateral suprasylvian neurons].

A linear interrelationship exists between the size of the receptive field in the middle suprasylvian area and the distance of the field center (up to 30 degrees) from the glance fixation point. The slope of the regression line describing this interrelationship was shown to be different for the receptive fields situated along either vertical or horizontal meridians. The factor of magnification of the visual system's previous level seems to underlie the dependence of changes in the receptive fields size on the eccentricity.

Animals↗