Biomedical subjects
Publications and source records attributed to V V Khrenkova.
Mono- and bifocal visual influences of different modality and biological significance were found to cause a functional brain asymmetry in the Rana ridibunda. The mechanism is discussed.
Stationary visual stimuli and diffuse light induced mainly excitatory responses of the neurons. Among the neurons responding to visual stimulations many units were the polysensory cells responding also to tactile and sound stimuli. The questions of organization of the tegmental neurons' visual receptive fields, are discussed. Prevalence of large receptive fields has been noted, mainly excitatory those or having an excitatory center and inhibitory periphery.
The space and time organization of neuronal activity was studied in the frog tectum opticum under the action of different visual stimuli. It is shown that inhibition plays an important role in neuronal reactions. It is suggested that differences in the space time parameters of neuronal activity reflect differences in visual signals which bring optic information from the retina.
Using coupled microelectrode studies of the frog tectum neuronal responses to diffuse light or moving visual stimulus, the excitatory-inhibitory constructions were revealed in the midbrain tectum. The size of excitatory areas of these constructions is about 100-200 mu with intevening inhibitory areas. It proved possible to find a correlation between the size of the excitatory tectal constructions appearing in different types of visual stimulation and the width of the branching areas as well as the site of terminals of the visual afferents and intratectal fibers.
Possible mechanisms of optic information encoding in the frog tectum are considered on the basis of the extracellular recording of the tectum neuron impulse activity. It is suggested that optic information is coded in the frog tectum by means of space coding and is made more precise with the help of different types of time-coding, the coding by latency difference being used more widely. This mechanism may function either independently or be a component of complex time-codings. A uniform distribution in the tectal structures of neurons processing optic information indicates that the mechanism of exact analysis of optic stimulus movement parameters should be a distribution function of the same structures.
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The greatest coherence of responses and latency for neuronal pairs was found at interelectrode distances up to 300 microns which is due, apparently, to dimensions of the afferent fibers' branching areas. The adaptation and extrapolation features observed in majority of the neurons, were more obvious in the tectum nuclear layers rather than in the fiber those. The more stable responses of the fiber layers' neurons suggest a representation of branches stemming from the fibers of the retina ganglionic cells, while in the nuclear layers the elements with high adaptability: the "novelty neurons", are localized.
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A study of neuronal responses of frog tectum to diffuse light and a moving visual stimulus, in which paired microelectrodes were used, disclosed the excitation-inhibition constructions originating in the midbrain tectum in response to various forms of visual stimulation. It was demonstrated that the dimensions of the excitation zones of these constructions are 100-200 mu in cross section, and are separated by inhibition zones. The dimensions of the excitatory tectal constructions resulting from various kinds of visual stimulation correlated with the width of the branching zones and locations of terminals of the afferents and intratectal fibers.
Tectal directionally selective neurons were investigated in frogs. The highest measure of agreement in the character of response and dynamics of latent periods of neuron pairs was found with interelectrode distances of up to 300 mu, a fact which is evidently connected with the dimensions of the zones of ramification of the afferent fibers. Adaptation and extrapolation properties were discovered for most neurons and they were more marked in the nuclear layers of the tectum than in the fibrous layers. The more stable responses of neurons in the fibrous layers indicate the possible representation there of branches of fibers of the retinal ganglion cells, whereas neurons with high adaptivity (novelty neurons) are located in the nuclear layers.