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V D Glezer

Publications and source records attributed to V D Glezer.

At least 19 recordsLinked to original sources
PubMed1979

[Inhibition and space-frequency characteristics of the complex receptive fields of the cat visual cortex].

Responses of complex receptive fields of the cat straitum to moving sinusoidal grating were studied. Stimulation of the receptive field with some spatial frequencies suppresses spontaneous discharges. Responses of the receptive field corroborate previously made predictions that the spatial--frequency characteristics of the receptive field should have the main and the secondary maximums and negative areas in case the complex fields perform piece-wise Fourier--transformation of image. The changes of impulse frequency in field's response are predicted by comparing the changes of instantaneous spectrum of grating entering the field with spatial frequency characteristic of the field. The data evidence that the complex field is rather a spatial--frequency filter than a detector. Some complex fields reveal a lateral inhibitory area behind the field's nucleus in direction of stimulus movement. The complex fields with no lateral inhibitory areas seem to serve for piece Fourier--description of image, those with lateral areas--for picking out the countour between textures.

Animals↗
PubMed1979

[Receptive fields of the visual cortex--detectors or filters of spatial frequencies?].

Spatial frequency characteristics of the complex cortical visual receptive field were studied in curarized cats. It is shown that, besides the main maximum, they also have additional maxima and negative regions as predicted by the theory of piecewise Fourier-analysis. Comparison of responses of the complex receptive field to sinusoidal grating entering the field completely or incompletely together with the comparison of responses to sinusoidal and squarewave gratings shows the linear properties of the receptive field as a spatial frequency filter. The response of the complex receptive field increases with the number of periods constituting the sinusoidal grating. Several periods of optimal spatial frequency matched the size of the complex receptive field. In the columns of neurons, the receptive fields were found tuned to a broad band of spatial frequencies. The data confirm the hypothesis according to which the complex receptive fields are rather spatial frequency filters than detectors.

Animals↗
PubMed1978

[Piecewise Fourier analysis of images and the role of the occipital, temporal and parietal cortex in visual perception].

On the basis of previously published data, a neuronal scheme of organization of the visual perception in the cerebral cortex, is suggested. An idea of neuronal module is introduced: a cylinder of cortical neurons whose receptive fields are directed towards the same area of the visual field and respond to different spatial frequencies and orientations. A system of overlapping modules is able of piece--wise Fourier--description of portions of the image. The modules of the Clare--Bishop area are composed of receptive fields of different size. Owing to that each neuron of the module projects inhibitory influence upon other neurons, the module acts as a filter picking out the texture. Therefore, the modules of the Clare--Bishop area single out and supply Fourier--description of subimages, the latters being characterized by the same local spectrum within their own limits. The lower portiön of temporal cortex performs a rough identification of subimages and images with the aid of systems of learning neurons. The parietal cortex conforms the description from temporal cortex to the complete description in the modules of occipital cortex, thus performing the transition from an image to a concrete picture.

Animals↗
PubMed1977

Local spectral analysis in the visual cortex.

On the basis of experimental evidence presented earlier a model of local spectral analysis of the image performed by the complex receptive fields of the visual cortex has been proposed. An essential feature of the model is that the generalized piece-wise Fourier transform is performed not over the image luminance function but over the logarithm contrast function resulted from analysis of the image by the round receptive fields of the preceding levels. Such an assumption removes a number of experimental objections offered against the hypothesis of two-dimensional Fourier transform in the visual system. The consequences from the piece-wise expansion in a series of basic functions have been considered and among them: the channel frequency characteristics which can have more than one maximum; the possibility of describing the image by a limited number of channels with overlapping frequency characteristics; the existence of mechanisms for estimation of phase shift between frequencies.

Models, Neurological↗
PubMed1975

[Neurophysiological mechanism of brightness scaling].

A model of statistical decisions was used to reveal the measure of neural activity according to impulse reactions. Effectiveness of two possible measures was compared: number of spikes in groups and instantaneous frequency. The former one provides greater probability of correct estimation of brightness at a lesser error probability. Neurophysiological scales of brightness were obtained in the form of dependences of index d' on the stimulus intensity. The dependences were the power those in all cases of analysis. The exponent depends on the stimulus size and alters like the exponent of psychological scale for quantitative estimations on alteration of the stimulus space. The same dependence of subjective estimation on intensity of the light stimulut is preserved for psychophysiological scales of grouping on scaling by 5-, 10- and 20-grade scale of a single set of illuminations. This shows that the brightness neurophysiological scale formed at the first stage of perception is independent of the rules of decision making at the second stage of perception.

Animals↗
PubMed1975

[Types of receptive field in the external geniculate body and its functional model].

The functional differences between receptive fields of types I and II of lateral geniculate nucleus were investigated in cat. Some characteristics of these fields are shown to coincide with transient (Y-type ) and sustanied (X-type) receptive fields. Receptive fields of type I possess a limited range for transmission of information on luminance, those of type II--a normal dynamic range (2 log. unit). The investigation of a dynamic functional model showed that type of the receptive field is determined by the depth of inhibition mediated through an interneuron. The depth of inhibition is larger in type I. Types I and II have different frequency characteristics. It is suggested that receptive fields of type I serve to transmit information on the shape of the image (spatial and time contrasts) and those of type II on luminance.

Animals↗
PubMedDate not supplied

[Adjustment of the cat visual cortex receptive fields to certain spatial frequency bands within definite ranges of movement frequencies of stimulating gratings].

Reactions of simple and composite receptive fields (RF) of the 17th and 18th fields of cat's visual cortex to grating with various spatial frequency moving through the field with different velocities were studied. It has been shown that for each RF the velocity range is revealed within which spatial-frequency selectivity of RF exists. The narrow-band tuning for high frequency RF exists in the range of low velocities, and for low frequency ones in the range of higher velocities.

Animals↗
PubMedDate not supplied

[Model of local spectral description of images in the visual system].

On the basis of experimental evidence presented earlier a model of local spectral analysis of the image performed by the complex receptive fields of the visual cortex has been proposed. An essential feature of the model is that the generalized piece-wise Fourier transform is performed not over the image luminance function but over the logarithm contrast function resulted from analysis of the image by the round receptive fields of the preceding levels. Such an assumption removes a number of experimental objections offered against the hypothesis of two-dimensional Fourier transform in the visual system. The consequencies from the piece-wise expansion in a series of basic functions have been considered and among them: the channel frequency characteristics which can have more than one maximum; the possibility of describing the image by a limited number of channels with overlapping frequency characteristics.

Fourier Analysis↗