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Biomedical subjects

A N Radchenko

Publications and source records attributed to A N Radchenko.

13 recordsLinked to original sources
PubMedDate not supplied

[Distribution of neural memory, loading factor, its regulation and optimization].

Recording and retrieving functions of the neural memory are simulated as a control of local conformational processes in neural synaptic fields. The localization of conformational changes is related to the afferent temporal-spatial pulse pattern flow, the microstructure of connections and a plurality of temporal delays in synaptic fields and afferent pathways. The loci of conformations are described by sets of afferent addresses named address domains. Being superimposed on each other, address domains form a multilayer covering of the address space of the neuron or the ensemble. The superposition factor determines the dissemination of the conformational process, and the fuzzing of memory, and its accuracy and reliability. The engram is formed as detects in the packing of the address space and hence can be retrieved in inverse form. The accuracy of the retrieved information depends on the threshold level of conformational transitions, the distribution of conformational changes in synaptic fields of the neuronal population, and the memory loading factor. The latter is represented in the model by a slow potential. It reflects total conformational changes and displaces the membrane potential to monostable conformational regimes, by governing the exit from the recording regime, the potentiation of the neurone, and the readiness to reproduction. A relative amplitude of the slow potential and the coefficient of postconformational modification of ionic conductivity, which provides maximum reliability, accuracy, and capacity of memory, are calculated.

Animals↗
PubMedDate not supplied

[The precision parameters of visual perception].

Here we demonstrate that retina resolution is a system parameter, depending not only on the size of receptive fields (RF) of the ganglion cells (GC), but as also on their number and the picture complexity. The curve of visual perception accuracy as a function of these three variables is nonmonotone with pronounced extremum corresponding to the RF size. The system approach allows us to reconsider the accuracy of picture approximation by various retina zones, while its application to the on- and off-subsystems of GC reveals a new function of the lateral geniculate bodies (LGB) which is to processes these afferents. We have deciphered "abnormal" alternation of ipsi- and contralateral projections in the six LGB layers. Neural network simulation demonstrated that LGBs improve the reception accuracy; being transparent for accurate reception they screen out indistinct reception and block its access to the visual cortex. Resumption and refinement of the screened information is related to eye movements and to superior colliculi (SC) assuming that SC inverses LGB function, allocating the map of indistinct pixels (image contours) by processing the on- and off-afferens.

Afferent Pathways↗
PubMedDate not supplied

[Interlevel relations in neural memory: extrasynaptic reception of mediators, potentiation, and spontaneous activity].

The firing of "spontaneous" spikes is regarded as a result of mediator propagation to extrasynaptic receptors. Receptor-receptor interaction unites them in dimer and dimer clusters, which accept three conformational states under agonist action. There are two cooperative and potential dependent transitions between the states, where cluster accumulates or releases energy. The released energy can trigger a mechanism of endogenous (spontaneous) neuron firing in potentiation condition. These accumulating and triggering properties are absent in third (passive) conformational state, where gating charges immobilization reduces conformational mobility. The features of ionotropic, metabotropic and combined mediator action are discussed for different level of slow potential. Conformational effect depends on conformity of pattern space-temporal structure to geometric and functional features of metabotropic mediator sources in cluster environment. Each cluster appears to be adjusted for recognizing a certain vast set of afferent patterns. Number, structure and dimensionality of the recognized patterns are given by: 1) threshold of conformational transition, 2) allocation of synaptic and extrasynaptic mediator ejecting points in gap-hole environment of the receptive cluster 3) combinatorial connections of presynaptic cells with inhibit and excite synapses and 4) signal delays in presynaptic ways and neuropil. Numerous receptive clusters of soma-dendrite membrane are capable to write down information, to keep and accumulate it and to recover. Engram stored as passive/active conformational receptive cluster states is recovered in inversion by "spontaneous" neuronal activity. The original information may be recovered by reading via inhibit synapses.

Action Potentials↗
PubMedDate not supplied

[Effect of sizes of the retinal receptive field on the precision of image perception].

A paradox of sharp vision regardless of relatively large receptive fields of the retina is discussed. Transformation of images by the receptive fields or intersecting fields of vision of omma-tidia of the complex eye is described as an approximation of Bool functions by the implicant forms. Such an approximation results in the information compression. The compression coefficient is determined by the ratio between the implicants number and the number of points in the field of determination of the Bool function. The approximation errors strongly depend on the size of the receptive fields. With their increase the error abruptly decreases and only after passing the deep minimum it begins to slowly increase. The mechanism of information compression is a universal one and is similarly realized on the retina, facet and t.v. sets.

Humans↗
PubMedDate not supplied

[Hysteresis properties of excitable membranes--the basis for neuronal memory].

It is supposed that "fixed" membrane charges are spaced on protein lateral chain terminals and have limited ability to move with the chains. Interactions of the charges that are located on the opposite sides of the membrane depend on the membrane potential and can be described by a hysteresis volt-conformation characteristics with trigger transitions for one stable state to another. The value of the charges, that are shifted in the hysteresical loop limit, is close to the experimental data for gate currents. Possibility of interaction of chemoreceptive and electroexcitable mosaics of the neuron somato-dendrite membrane in eeg forming process is analysed.

Cell Membrane↗
PubMedDate not supplied

[Optimization of randomly organized distributive associative memory].

Sub- and intersynapsal randomly placed mosaics of somato-dendritical membrane are regarded as a neuronal memory system. The first (linear) subsystem seems as a mean for access (addressing) to the second (nonlinear, hysteresis) one. An informative model is created and optimal relations are detected on the threshold, geometrical and temporal parameters of the synapse fields. The relations being settled transform the synapse field to associative memory with optimal distributive features. The reliability of such memory is equal to one of the holograms.

Cell Membrane↗
PubMedDate not supplied

[Recording, consolidation, and reproduction of information in the neuronal memory].

The electroexcitable mosaic of neuron SD-membrane is considered to be a hysteresis medium: a set of bistable memory units (MU) that capture or give back the energy in state transitions. The consolidation is shown to be achieved by inactivation of a part of MU (which had lost their energy) by means of transit of their volt-conformative characteristics to the non-hysteresis form. The MU hysteresis features are the result of moderate mobility of the membrane charges. The consolidation results in immobilization of the charges. It seems that immobilization of gate charges is the same phenomenon. Great importance of time delay pertaining to this process is emphasized. The time delay and working point shift beyond the hysteresis loop limits into the hyperpolarization side ensures the non-destructive reading.

Cell Membrane↗
PubMedDate not supplied

[Role of the exterior geniculate bodies and superior colliculus in the system that collects and accumulates visual information].

An analysis of picture on- and off-decompositions by retina ganglion cells and ipsi- and contralateral projections interleaving in lateral geniculate bodies (LGB) layers lead to founding earlier unknown LGB function-the logic filtering of the accurate (common in two approximations) parts of images. On- and off-splitting guarantees non-depended picture over and below approximations and reliable performing the above filtering function in the LGB layers. System complementation to LGB function is retinotopic mapping of non-percept pixels. It relates to primary superior colliculus (SC) function. Correlation between LGB and SC functions and saccade eye movements is discussed. Neurological nets for LGB and for a part of SC which realize the specified processor functions are presented.

Geniculate Bodies↗
PubMedDate not supplied

[Effect of the mobility of gate charges on volt-ampere characteristics of excitable membranes].

An assumption on nature of the gate charges and known data on gate changes mobility allow to deduce the volt-ampere characteristics of ionic channels and the same for membrane. Model research shows that the volt-ampere curve shape depends on gate charges mobility. Its reduction and the followed gate charges immobilization during membrane excitation process are expressed as the changes of volt-ampere curves. These changes might be to specify as the fast components of the inactivation process. A number critical values of the gate charges mobility are calculated which are important for the functions of memory (hysteresis) and excitation (negative resistance). The coincidence of values of biased charge in model and experiment is noted. The formulae that are drown are compared with Hodgkin-Huxley approximations.

Electrochemistry↗