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We have studied the contrast sensitivity of the visual system in various ranges of the spatial frequencies in “dry” immersion conditions that simulate the physiological effects of microgravity. The contrast sensitivity in the range of low and high spatial frequencies is indicative of the functional state of the magnocellular and parvocellular neuronal pathways that form the dorsal and ventral information flows from the occipital to the frontal lobes. The study involved ten volunteers who were exposed to “dry” immersion for 21 days. The contrast sensitivity of the visual system was recorded with a method of visocontrastometry. The Gabor elements were used as stimuli. An increase in contrast sensitivity was registered in the low spatial frequency range with specific sensitivity of the magnocellular pathway to these frequencies on the third day of immersion and 1 day after the end of the experiment, compared to the background values. The contrast sensitivity in the high spatial frequency range with specific sensitivity of the parvocellular pathway to these frequencies in the experiment remained unchanged. Thus, our findings have shown that the magnocellular neuronal pathway is involved in the processes of adaptation to extreme ambient conditions.

The purpose of this study was to investigate the relationship between the morphological parameters of the fovea, foveola, and foveolita of the human eye and the psychophysical and electrophysiological indices of the sensory and cognitive activities. We investigated the relationship between the sizes of these structures and the resolving power of the eye, as well as the influence of the size on the amplitudes and latent periods of various evoked potential components. It has been found that the foveola diameter affects the latent periods of the early waves of the visual evoked potentials (component P100) in the occipital areas. Our data confirm the effect of the foveola diameter on the parameters of cognitive processes during reading. In particular, it has been found that a larger fovea size provides the perception of a higher amount of printed characters.

Behavioral experiments were performed in which rhesus macaques were trained to interact with a computer using a touchscreen. Stimuli consisted of semitone images of Gabor elements with low spatial frequency with different contrast levels. The monkeys’ task was to touch the screen with the paw at the site at which the target stimulus appeared, which was followed by automatic delivery of a food or drink (juice) reward. Contrast was gradually decreased when correct responses were obtained. A two-way forced choice paradigm was used to measure the threshold contrast at which the monkeys could detect the appearance of low-frequency images. Decreases in the spatial frequency of stimuli were accompanied by decreases in contrast sensitivity, while reaction times increased. These data widen our understanding of primate activity in a virtual environment and make it possible to model and study a variety of human diseases.

The paper describes the results of studies aimed at evaluating the effect of interactive virtual environments on the visual system, including the magno-and parvo-systems. Analysis was conducted in patients diagnosed with paranoid schizophrenia diagnosed from one to five years ago. Comparative analysis of visual evoked potentials during the perception of images that differed in their semantic (animate/inanimate) and physical characteristics (filtration images at high/low spatial frequencies) was used for the assessment of the impact of virtual environments. The images of objects were filtered via digital filtration for selective effect on the magno-and parvo-channels of the visual system. To evaluate the function of visual perception, the measurement of contrast sensitivity using Gabor elements was used. At the early stages of schizophrenia, the patients exhibited a decrease in the amplitudes of the components of cognitive visual evoked potentials to stimuli filtered at high spatial frequencies and reduced contrast sensitivity at high spatial frequencies. The effect of virtual environments on the visual system resulted in a significant increase in the amplitude of the cognitive components of visual evoked potentials in the paradigm of presentation of images filtered at the high spatial frequencies, which allows the conclusion about a stimulating effect of the virtual environment on the parvo-system functioning. The activation of the magno-system occurred to a lesser extent. The present study represents the findings obtained by the studies of cognitive impairments in schizophrenia and the methods of their correction conducted at the Laboratory of Physiology of Vision of the Pavlov Institute of Physiology of the Russian Academy of Sciences and at the Laboratory of Neurobiology of Action Programming of the Bechtereva Institute of the Human Brain of the Russian Academy of Sciences.

We studied the characteristics of evoked potentials recorded during the recognition test based on four types of series of images subjected to the wavelet filtration: images of living objects containing either low frequency or high frequency portion of the spatial frequency spectrum, and imaging of non-living objects in the same two spatial frequency bands. Each subject had to classify the image either by its semantic feature (living–non-living), or by its physical feature (low frequency–high frequency). The purpose of this study was to compare the time characteristics of evoked potentials in these two types of tasks, which provides information on the time characteristics of categorization mechanisms of visual images. Analysis of the latent periods and amplitudes of the components of evoked potentials allowed us to detect the occipital areas of the leads where the early components (up to 170 ms) are associated with spatial and frequency characteristics of the image, the frontal and temporal areas where the components of 170–200 ms correspond to the process of categorization, and the later frontal, central, and parietal areas (300–500 ms) correspond to the process of error detection and the organization of motor response.

Biederman and co-authors [1, 2], have shown that the priming effect in the long-tirn priming paradigm does not depend on the difference between the angular sizes of the test stimulus and the primer. However, these two and other similar works (both with long-time and short-fime priming paradigms) studied a small range of the angular sizes of stimuli. In Vakhrameeva et al. [3], it has been shown that there exist two perceptionally different size ranges: perception of the objects with angular size varying from 1-1.5 to 50 deg was found to be invariant, but for the objects which angular size is less than 1-1.5 deg (depending on object class and task) their perception is no longer invariant. In this work we have investigated the presence of priming effect in match-to-sample task with such a difference in the angular sizes of a primer and a test stimuli, when the sizes of the primer (about 4 deg) and the test stimulus (about 0.5 deg) belong to those different physiological size ranges. The sample stimulus was presented with and without the noise superposition. It has been shown that the priming effect is suppressed when the size difference between the primer and the test stimulus is large. A congruent primer can give a positive impact on the recognition of the test objects, but this takes place under viewing conditions complicated by the noise superposition.

An image-classification algorithm based on an alphabet of local binary patterns is described. The efficiency of the proposed algorithm is demonstrated using a test image set of handwritten digits (MNIST). A comparison of the algorithm’s properties with similar results to those of convolutional artificial neural networks is presented.

The eye resolving power and human visual acuity are the most important parameters of physiological optics. In this study, we compare our results of psychophysics, subjective measurement of visual acuity, with the results of electrophysiological measurement, objective measurement of visual acuity using vanishing optotypes that differ in spatial (sharp or non-sharp) and semantic (animate or inanimate) properties. The subject is instructed to provide consciously the classification of images: are they sharp, or are they non-sharp. At the same time the subject unconsciously provides another classification: what objects presented to him as images are animate or inanimate. This unconscious classification was provided by the subject without instruction to do it, and it was independent of his conscious decisions made during testing of the presented images of the objects (sharp or non-sharp). We see the observer’s unconscious classification (animate or inanimate) only using electrophysiological measurements. The markers of unconscious recognition are the visual evoked potential components P200 and N170, recorded from the frontal brain area. The discovered effect works as an instrument for objective visual acuity measurements.

This study is devoted to the search for electrophysiological indicators of the human perception of a threat in a complex background target environment. It is shown that the human visual system can distinguish between threatening and nonthreatening stimuli at an unconscious level, and the primary stages of image processing are similar to those during conscious perception. An increase in the amplitude of the positive wave of the evoked potential with a latency period of 320 ms and a decrease in the amplitude of the electroencephalogram rhythms at a frequency of approximately 12 Hz in the range of 350–750 ms after presentation of a threatening stimulus can serve as electrophysiological indicators of unconscious perception. The results obtained are considered from the perspective of the matched filtration model.

This paper proposes a principle for synthesizing a complex target environment and identifies the optical masking characteristics for unconscious perception of a signal. A signal hidden by masking is supplied on the periphery of the field of view for a short time interval, unconsciously activating wide-angle human “periscopic vision” that possesses low spatial and high temporal resolution. In these studies, the selective attention of the narrow-angle central-vision channel with high spatial resolution was charged with a pseudotarget. We assumed that peripheral vision is capable at that instant of unconsciously perceiving signals hidden by a mask and storing them in memory. It was established that the unconscious low-frequency descriptions of the signals stored in memory influence decision making and control the operator’s involuntary motions under conditions of indeterminacy. Opponent-style implementation of the interaction of central and peripheral vision can serve as a pattern for further refining artificial control systems.

In behavioral experiments rhesus macaque monkeys were trained to interact with the computer using a tactile display. We used grayscale Gabor patches of low spatial frequency as stimuli. Monkeys' task was to touch the screen with his hand in the area of the target stimulus, followed by automatic food or juice reinforcement. After two successive correct answers, stimulus contrast gradually decreased. Using a two-alternative forced choice method the contrast threshold was measured within which monkeys can detect the appearance of low-frequency images. It was shown that the contrast sensitivity decreased with the decrease of stimulus spatial frequency, while the reaction time increased. The findings extend our knowledge of the primates' activity in the virtual environment and open new possibilities for modeling and studying various human diseases.

Biederman and co-authors [1, 2], have shown that the priming effect in the long-tirn priming paradigm does not depend on the difference between the angular sizes of the test stimulus and the primer. However, these two and other similar works (both with long-time and short-fime priming paradigms) studied a small range of the angular sizes of stimuli. In Vakhrameeva et al. [3], it has been shown that there exist two perceptionally different size ranges: perception of the objects with angular size varying from 1-1.5 to 50 deg was found to be invariant, but for the objects which angular size is less than 1-1.5 deg (depending on object class and task) their perception is no longer invariant. In this work we have investigated the presence of priming effect in match-to-sample task with such a difference in the angular sizes of a primer and a test stimuli, when the sizes of the primer (about 4 deg) and the test stimulus (about 0.5 deg) belong to those different physiological size ranges. The sample stimulus was presented with and without the noise superposition. It has been shown that the priming effect is suppressed when the size difference between the primer and the test stimulus is large. A congruent primer can give a positive impact on the recognition of the test objects, but this takes place under viewing conditions complicated by the noise superposition.

We studied the characteristics of evoked potentials recorded during the recognition test based on four types of series of images subjected to the wavelet filtration: images of living objects containing either low frequency or high frequency portion of the spatial frequency spectrum, and imaging of non-living objects in the same two spatial frequency bands. Each subject had to classify the image either by its semantic feature (live-not live), or by its physical feature (low-high frequency). The purpose of this study was to compare the time characteristics of evoked potentials in these two types of tasks, which provides information on the time characteristics of categorization mechanisms of visual images. Analysis of the latent periods and amplitudes of the components of evoked potentials enabled to detect the occipital areas of the leads where the early components (up to 170 ms) are associated with spatial and frequency characteristics of the image, the frontal and temporal areas where the components of 170-200 ms correspond with the process of categorization, and the later frontal, central and parietal areas (300-500 ms) correspond with the process of error detection and the organization of motor response.

A software–hardware complex for studying the neurophysiological mechanism that controls saccades is described and makes it possible to generate images using the motion of a window synchronized with eye movement. This complex makes it possible to demonstrate to the subject either the part of the image perceived only by the foveal region or the part perceived by the periphery of the retina.

This study investigates the markers of operation of the classification mechanism that is invariant to scale transformations of images of test objects. Observers were asked to classify images according to the criterion of animate/inanimate object. Two series of studies were conducted using the method of cognitive evoked potentials. The angular sizes of the image of the objects presented to the observer were 3° in one series and 0.4° in another. It was established that the classification of the images of the stimuli of various angular sizes according to semantic features (animate/inanimate) causes a difference in the amplitudes of the P200 components (in the leads F7 and F8 of the frontal area). The role of the P200 components of the evoked potentials in the frontal areas of the brain as a marker of the classification process was investigated. It is observed that neural networks of the prefrontal cortex use the invariant description of images implemented in the previous stages of their processing to perform the classification of objects.

The results of a study on the corrective effect of training using a visual-motor focused activity in a virtual environment on the functioning of the visual system of patients with depression are presented. The effects were evaluated using the method of cognitive visual evoked potentials. Digitally filtered images were used as visual stimuli in measuring such potentials. It was shown that in patients suffering from depression, the early stages of processing visual information are disrupted, mainly by the parvo channels, and stimulation using virtual reality systems makes it possible to correct these disruptions.

This paper discusses the characteristics of eye movement in tasks of recognizing texts and comics with descriptions of dynamic genre scenes. The interconnection of the semantic space of the comics mentally constructed by the observer and the semantic space of test images constructed by the researcher is analyzed by measuring the characteristics of eye movements, which play the role of a distinctive marker that projects onto the test object a subjective algorithm for analyzing the content. The common features inherent to the distribution of saccades and fixations of the gaze in image space when comics and textual images are being experienced probably reflect the algorithm for detecting the semantic, conceptual structure of images common to the analysis of different methods of transferring information in multimedia. This algorithm breaks down under various diseases of the brain. It is assumed that, regardless of the difference of representing information in texts and comics, understanding is provided by common mechanisms for constructing the internal, imaginary, time-varying content.

The most sensitive methods to detect pathological changes in the visual system are the method of recording visual evoked potentials and the psychophysical method of measuring contrast sensitivity. Described in the literature features of functional disorders of the visual system in patients with multiple sclerosis are controversial. The results of the study allowed us to make an assumption about the depen-dence of the nature and severity of changes of the evoked potentials and contrast sensitivity and the duration of disease in patients with multiple sclerosis. In some patients with disease duration from 3 to 10 years there are irregularities in the magno-channels (reduced amplitude component P1), in others-- parvo-channels (amplitude reduction N 1) without increasing the latency, in patients with a disease duration of 10 to 14 years--both channels dysfunction (decreased amplitude components P1 and N1) with an increase of latency. The data indicate heterogeneity of pathophysiological changes upon increase of the degree of demyelination and damage of optic nerve fibers in multiple sclerosis.

The interaction between the mechanisms of local and global image analysis at the level of the magnocellular and parvocellular channels of the human visual system was studied. Using wavelet filtering, the spatial frequency composition of texts presented to observers was varied. It was shown that gradual blurring of texts via wavelet filtering interferes with the work of the parvocellular system but simultaneously increases the contribution of the magnocellular system during reading. With an increase in the wavelet element scale, the parvocellular system receives insufficient information for effective work, and in this situation the magnocellular system determines the strategy of eye movements. In addition, the necessary frequency range that ensures the functioning of the reading process is provided.

This paper describes an algorithm for distinguishing between images of two classes of objects: artificial and natural. An approximation to the image is generated using graphical elements similar to the receptor fields of neurons in the primary visual cortex (Zone VI). We show that the approximation-error distribution for natural-object images lies at higher values of the approximation error than that for artificial-object images. This difference makes it possible to detect artificial objects against natural backgrounds.

The aims of this study were to identify the locations of areas in the human cortex responsible for describing fragmented test images of different degrees of ordering and to identify the areas taking decisions regarding stimuli of this type. The locations of higher visual functions were determined by functional magnetic resonance imaging (fMRI) using a scanner fitted with a superconducting magnet and a field strength of 1.5 T. The blood oxygen level-dependent (BOLD) method was based on measurements of the level of hemoglobin oxygenation in the blood supplied to the brain. This level was taken to be proportional to the extent of neuron activation in the corresponding part of the gray matter. Stimuli were matrixes consisting of Gabor elements of different orientations. The measure of matrix ordering was the ratio of the number of Gabor elements with identical orientations to the total number of elements in the image. Brain neurons were activated by simultaneous changes in the orientations of all the elements, leading to substitution of one matrix by another. Substitution of the orientation was perceived by observers as rotation of the elements in the matrix. Stimulation by matrixes with a high level of ordering was found to activate the occipital areas of the cortex, V1 and V2 (BA17-BA18), while presentation of matrixes with random element orientations also activated the parietal-temporal cortex, V3, V4, V5 (BA19), and the parietal area (BA7). Brain zones responsible for taking decisions regarding the level of order or chaos in the organization of the stimuli are located in different but close areas of the prefrontal and frontal cortex of the brain, including BA6, BA9, and BA10. The results are assessed in terms of concepts of the roles and interactions of different areas of the human brain during recognition of fragmented images of different degrees of complexity.

A method for the synthesis of cyclic β-(trifluoroacetyl) enamines was proposed. Reactions of the latter with hydrazine and hydroxylamine gave pyrazoles and isoxazoles, respectively, containing trifluoromethyl and ω-aminoalkyl fragments. Addition of hydrazine (hydroxylamine) to the above amino enones was regiospecific, the regiochemistry of the heterocyclization of trifluoromethyl ketones being different from that for nonfluorinated analogs.

Electrophysiological studies were performed to measure the threshold (upper end of range) spatial frequency using visual evoked potentials and comparison with visual acuity neuron 26 healthy subjects. The aim of the present work was to create a method for objective measurement of visual acuity. This was addressed by initial measurements using a universally accepted method of visual stimulation and processing of electroencephalograms, which allows errors due to individual differences in visual system function to be minimized. These experiments yielded a strong correlation between the threshold spatial frequency of the test grid yielding an evoked potential on presentation and visual acuity, in degrees, expressed as the resolving ability of the visual system for this optotype. A logarithmic relationship was found between these values and an equation allowing automated calculation of visual acuity (resolving ability) from electrophysiological data was derived. The results were independent of the subject's responses and therefore provides a maximally objective assessment of visual acuity.

We measured susceptibility to the Müller-Lyer illusion in schizophrenic patients and normal observers. The images of the Müller-Lyer figure were digitally filtered in a high-frequency and low-frequency band by wavelet filter. Patients with schizophrenia are more susceptible to Müller-Lyer illusion, than mentally healthy examinees. The images of the Müller-Lyer figure with low spatial frequency were perceived in a similar way by the schizophrenic patients on the initial stage of disease and the control subjects. Patients with schizophrenia were more sensitive to the Müller-Lyer illusion when the image contained only high or medium spatial frequency. Schizophrenic patients in advanced stage were more susceptible to the illusion while presented with all types of images of the Müller-Lyer figure than the control group. It is hypothesized that those differences arise from the mismatch work of the magnocellular and parvocellular systems. It is known that images with the high spatial frequencies are most relevant for the parvocellular visual channels. The magnocellular visual channels are most sensitive to the images with the low spatial frequencies. Thus these findings demonstrate a significant impairment in parvocellular pathway function in patients on initial stage of schizophrenia. The patients on advanced stage of schizophrenia demonstrate impairment of both the parvocellular and magnocellular systems.

In order to better appreciate the neurophysiologic mechanisms of perception of length under conditions of geometrical visual illusions, we studied sensitivity of mentally healthy subjects and schizophrenic patients to Ponzo and Müller-Lyer illusion. Patients with schizophrenia estimated length of segments of Müller-Lyer figure less precisely. Accuracy of perception of length of segments in Ponzo figure was ambiguously connected with the duration of the disease. Persons suffering from schizophrenia for a short time were less inclined to Ponzo illusion than mentally healthy subjects. On the contrary, patients who suffered from schizophrenia for a long time were more sensitive to this illusion. Ponzo illusion can be used as a marker of schizophrenia which is found out during the specific period of development of the disease. High sensitivity of patients with schizophrenia to Müller-Lyer and Ponzo illusions supports a hypothesis about the role of the global analysis of an image during processing of its low-frequency component in formation of the illusions under study.

The purpose of the current research was to estimate the range of angular sizes of incomplete images across which the perception of the given images does not depend on scale. We have measured thresholds of recognition of the identities of objects across a wide range of angular sizes from 0.19 to 50 degrees of visual angle. The methodology derived from the Gollin-test which has been used as a method for studying the perception of objects presented as incomplete contour and pattern recognition. Results demonstrated that there is a wide range of angular sizes (from 1 .0 up to 50 degrees of visual angle) across which thresholds perception of incomplete images does not depend on object size. However, there was found a narrow range of small sizes of stimulus (0.19-1.0 degrees of visual angle) at which there was found dependence of performance on object size. We assume that increase of thresholds and occurrence of undistinguished images (when they have small size) depends on increase of the contribution of sampling noise at the observer's eye retina.

The aim of the present work was to assess the range of angular sizes of fragmented images of objects at which perception of the images was scale-independent. Measurements were made of human subjects' recognition thresholds for the shapes of the objects over a wide range of angular sizes (0.19-50 degrees). The experiments used the Gollin test--a method for studying the recognition of fragmented outline images of objects with which the observer is familiar. The results obtained demonstrated that there is a wide range of angular sizes, from 1.0 degrees to 50 degrees, over which the perception thresholds of incomplete outline images do not change with changes in size, along with a narrow range of stimulus sizes, 0.19-1.0 degrees, over which there is a significant size dependence. We suggest that the increase in thresholds and the failure to recognize images of small size occur as a result of an increased contribution of sampling noise at the level of the human retina.

This paper presents the results of a comparative computer analysis of monochromatic drawings by mentally healthy subjects and patients with schizophrenia. The contours of the images were distinguished in each of the drawings, after which the following characteristics were calculated: the total length of all the contours of the image, the mean size of the image, and the ratio of the total length of the contours to the mean size. The spatial-frequency spectra of the images were also computed. It is established that the mean size of the drawings and the relative length of the contours in the drawings by the patients with schizophrenia are less than in those of the healthy subjects—i.e., the drawings of the patients with schizophrenia are less detailed. Moreover, these drawings are characterized by a certain rise of the spectrum in the region of medium spatial frequencies. As shown by a computer experiment, on the basis of an analysis of twenty arbitrarily chosen drawings by the patients with schizophrenia, a positive diagnosis can be delivered in 92% of all the cases. When the same sample of drawings by healthy subjects is analyzed, the probability of an incorrect diagnosis was 6.5%. The resulting data are regarded as evidence of dysfunction when there is schizophrenia of the magnocellular system, which provides a global analysis of the images and an increase of the internal noise level of the visual system.

This article gives an analysis of the interconnection of the optical properties of incomplete (fragmented) images and the psychophysical recognition thresholds of objects as necessary conditions for the appearance of visual insight. A well-known method of measuring the perception thresholds of fragmented images—the Gollin test—is proposed for the first time for solving the problem of evaluating the characteristics of insight in a person. The architecture of the neural networks that ensure the appearance of insight is considered.

The work of an operator in solving two classification problems when working with one image alphabet is studied. From ninety visual stimuli, half of the images contained animate objects, and the other half contained inanimate objects. The first task was to classify the images according to a semantic attribute—whether they contained an animate or inanimate object. This alphabet of stimuli was then subjected to wavelet filtering in a low- and high-spatial-frequency region, regardless of semantic significance. The second task was to classify the stimuli according to a physical attribute—a blurred or unblurred object in the image. Electrophysiological monitoring of the operator’s work—recording of the induced visual potentials from the entire surface of the head—made it possible to detect that, from the beginning of the stimulation until the organization of the motor response, parallel processing of the observed signal occurs according to the different semantic and physical attributes. The responses of the temporal and frontal sections of the brain associated with the semantics of the images are distinguished, even under those conditions in which the subject’s task was to classify the physical properties of an image of an object.

It is well known that an important function of binocular vision is to increase the SNR. When a signal simultaneously arrives along two channels, it is summed if the channels are statistically independent. The binocular visual acuity can then theoretically be increased by comparison with the monocular value by a factor of 2, or 1.4. This paper gives the results of experiments to measure the visual acuity by means of Landolt rings. It is established that binocular visual acuity is greater than monocular by a factor of 1.3 on the average. It is assumed that this can be associated with internal multiplicative discretization noise at the level of the retinal receptors. This result is important for understanding image processing in different channels of the visual system.

The methods of neuroiconics and functional magnetic-resonance tomography are used to investigate the factors that limit the possibilities of visual search. The influence of an image of a human face hidden in the background on the activity of the observer’s brain was recorded during the task of tracking a moving ring. It is established that images are unconsciously perceived under threshold-presentation conditions, and this is reflected in the activation of the fusiform gyrus—a region of the brain that participates in face recognition. Under above-threshold presentation conditions, the parietal and frontal regions of the brain were also activated, but activity in this case decreased in the auditory, motor, and certain other regions of the brain not occupied in signal processing. The resulting data reveal the significance of the background semantics under conditions of visual search and explain how the unconsciously perceived optical characteristics of a background image can affect the operator’s functional state.

We report here our electrophysiological and psychophysiological studies of the mechanisms by which the visual system recognizes structured images with different levels of ordering. Visual stimuli consisted of textures, i.e., a set of matrixes consisting of Gabor grids. Matrixes differed in terms of the degree of ordering resulting from changes in the probability that grids with the same orientation would appear. The subject’s task was to identify the dominant orientation in the stimulus. The relationship between response accuracy, reaction time, and the main characteristics of evoked potentials on the one hand, and the number of identical grids in the matrix on the other was identified. The proportion of correct responses increased and the reaction time decreased as the degree of ordering of stimuli increased. Visual evoked potentials recorded in the occipital areas showed a relationship between the amplitudes of the N2, P2, and P3 waves, with latent periods of 180, 260, and 400 msec, respectively, and matrix parameters. The amplitudes of the P3 component and the positive component recorded in the frontal leads, with a latent period of 250 msec, increased gradually as the task became simpler. The amplitude of the N2 wave also increased with increases in the number of identically oriented elements in the matrix, though this relationship was S-shaped. The magnitude of the P2 component, conversely, was maximal in response to presentation of those matrixes which were most complex to recognize and gradually decreased as the content of identically oriented grids in the matrix increased. These relationships were compared with the statistical characteristics of the stimuli and assessed in terms of the view that the visual system contains two mechanisms, i.e., local and integral image descriptions.

We measured recognition thresholds of incomplete figure perception (the Gollin test). This test we regarded as a visual masking problem. Digital image processing permits us to measure the spatial properties and spatial frequency spectrum of the absent part of the image as the mask. Using a noise paradigm, we have measured the signal/noise ratio for Incomplete Figure. Recognition was worse with better spectral "similarity" between the figure and the "invisible" mask. At threshold, the spectrum of the fragmented image was equally similar to that of the "invisible" mask and complete image. We think the recognition thresholds for Gollin stimuli reflect the signal/noise ratio.

The thresholds of recognition of line drawings of common objects were measured using the Gollin-test procedure, in which separate random line fragments are displayed cumulatively up to the point of recognition. It was shown that the mean percentage of contour displayed at threshold recognition for different images was always about 12.5%, despite inter-subject variability between 5% and 25%. The comparative and spatial-frequency analysis of the geometrical parameters of images was carried out for different levels of fragmentation (before threshold, at threshold, and for the complete contour). The magnitude information of the Fourier domain image of figures was characterized by maximum at low and high levels of fragmentation, but at recognition threshold fragmentation it was characterized by minimum variability.

This paper discusses the process of perceiving dynamic images subjected to processing with spatial-frequency filters that simulate the characteristics of the receptive fields of the neurons of the primary visual cortex. A technique was used that makes it possible to give a quantitative estimate of how subjects perceive the emotional state of people’s faces on images presented to the subjects. It was shown that, besides the vertical and horizontal components of the spatial-frequency spectrum, a substantial role is played by the diagonal components in the process of perceiving the images of faces. Even though the visual system is less sensitive to the diagonal components than to the vertical and horizontal ones, the information contained in them makes it possible to distinguish the individual features and emotional state of a person’s face.

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.

The development of methods of digitally synthesizing and processing images has made it possible to use the methods of iconics to deliberately create test images that selectively activate various structures of the visual system. The methods of processing neurophysiological data, including not only images of the activity of the entire brain but also so-called neuroimaging methods, have made it possible to discriminate the brain structures activated as a result of this selective action. The goal of this study is the spatiotemporal localization (mapping) of the regions of the brain that participate in making decisions concerning the shape of textures. It is established that a subject’s reaction time correlates with the degree of ordering of the textures and with the latency of the late components of the induced potentials in the frontal cortex. The time for a person to make decisions in the task of recognizing a specified class of textures is thereby determined. Mapping of the brain by the method of functional magnetic-resonance tomography showed that the activity of the brain in the process of making decisions involving recognition occurs in the frontal cortex of the human brain.

Psychophysical studies of the visual perception of incomplete contour images have been carried out. The images were synthesized by means of wavelets. The wavelets consisted of the difference-of-Gaussians (DoG) function and oriented wavelets whose spectrum is limited both in the frequency range and in the orientation range. The image size and the number and angular size of the wavelets were varied. The dependence between the characteristics of the wavelets and the recognition thresholds of the incomplete images was established.