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G A Kuraev

Publications and source records attributed to G A Kuraev.

At least 19 recordsLinked to original sources
PubMed2003

[Problem of visual segmentation and spatial-frequency filtration].

The analysis of the visual segmentation problem involved questions concerned with a signal description as a result of linear filtering, nature following nonlinear transformations, and possible role of a spatial attention in pooling. Different approaches to the visual segmentation problem are compared. Our data suggest a model of visual segmentation. It uses the universal principle of linear filters pooling at second-order mechanisms. The pooling mechanism is characterized by position, spatial frequency and orientation tuning an is selective in respect to pattern size. The most activated pooling mechanisms are "targets" for selective attention. It is shown that the information selected this way is necessary and sufficient for recognition. Multiple representation of a visual scene with different resolution and hierarchical principle of description organise the recognition as successive specification.

Attention↗
PubMed1995

[Biotropic effects of electromagnetic fields: benefit or harm?].

An overview contains the analysis of controversial literary data on possible therapeutic and pathogenic effects of electromagnetic fields on humans. The non-specific character of body shifts induced by electromagnetic fields with a prevalence of adaptive reactions at the onset and an emergence of dysadaptive processes during extremely long exposure was displayed. The leading role in the development of a therapeutic or pathogenic effect is played by the functional characteristics of an individual postulating the interaction of cumulative and adaptive processes in the body during long-term exposure in an electromagnetic field.

Adaptation, Physiological↗
PubMed1992

[Morphometric evidence of activation of axo-somatic synapses during administration of delta sleep-inducing peptide].

Computed morphometry proved activation of neocortex layer III-V axosomatic synapses. This is evident from an increase in the mean plasmalemma length, that in the active synapse zones on neurone bodies and width of the synaptic cleft, this being induced by a single intraperitoneal administration of delta-sleep-inducing peptide. The activation of the axosomatic synapses correlates with elevated GABA levels in the cerebral hemispheres cortex.

Animals↗
PubMedDate not supplied

[Informational characteristics of the impulse activity of cat sensomotor cortex neurons during elaboration of a defensive conditioned reflex].

Manifestations of the dynamics of defensive conditioning were studied in the cat sensorimotor cortical units. It has been shown that the process of learning is linked to the dynamics of the amount of total and useful information present in the evoked spike responses to a conditioned stimulus. As the pairings continue, the amount of useful information increases in reactions to conditioned or unconditioned stimuli and in the period preceding the conditioned stimulation.

Animals↗
PubMedDate not supplied

[Size as a parameter for tuning visual attention].

The ability of visual attention to tune to the stimulus size (when this size could not be described by spatial frequencies) was studies. Sinusoidal gratings with frequencies of 1.5, 3, and 6 cycle/degree were used as test stimuli. All these stimuli consisted of 3 periods, consequently, they had different sizes: 2 x 2, 1 x 1, and 0.5 x 0.5 degrees. Three reference stimuli had the same sizes but were constructed as a superposition of all the test frequencies. The reference stimulus of suprathreshold contrast was displayed for 400 ms to the left or to the right of a fixation point at a distance of 3 degrees. After that, the test stimulus of threshold contrast was for 100 ms displayed symmetrically to the fixation point on the other side. Subjects were instructed that the sizes of the reference and test stimuli were the same. It was found that the probability of test detection decreased with increase in the difference between the sizes of the reference and test stimuli. Since in our experiments the spatial frequency could not be used for tuning visual attention, the obtained results suggest that there are specialized mechanisms in the visual system for estimation of the general image size.

Attention↗
PubMedDate not supplied

[The neuronal organization of a focus of conditioned excitation in the cat sensory-motor cortex].

The activity of single units in the focus of conditioned excitation was studied during defensive conditioning to direct electrical stimulation of the cat sensorimotor cortex. Reorganizations of spike activity set in during the period of reflex elaboration, were manifest in the increased number of excited neurones and those which respond both to the conditioned and unconditioned stimuli. In the course of elaboration, the inhibitory phase of unit responses to direct electrical stimulation of the sensorimotor cortex was reduced, while the frequency of background unit spike activity was enhanced. Acute extinction of the reflex restored the initial duration of the inhibitory phase and reduced the frequency of the background activity.

Animals↗