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A Gutman

Publications and source records attributed to A Gutman.

158 records · Page 9Linked to original sources
PubMedDate not supplied

[Theory of EEG potential in a model of the thin membranes of the brain].

The methods of estimating a momentary value of the epidural potential using several values of EEG, sampled at the same instant, are explored theoretically. The weights of the summation of these EEG-potentials for the case of simple disposition of electrodes, are single-valued by means of elementary consideration of the potential theory and symmetry. The space filters of EEG obtained in such a way, were analysed on the basis of the model of thin integuments of the brains. The systems of 4--8 electrodes on the scalp are proposed for the estimation of mono- and bipolar ECoG's, which are less sensitive to ECoG of the remote cortex than ordinary derivations of EEG.

Cerebral Cortex↗
PubMedDate not supplied

[Theoretical analysis of an experiment with motor neuron voltage clamping. Proof of the N-shape of the steady-state volt-ampere characteristic of the dendrite membrane].

Current--voltage relation (I--V) in motoneurons [6] is discussed on the basis of the hypothesis [1] about N-shaped steady-state I--V for the dendritic membrane. A spontaneous discharge of motorneurons after clamp-off is interpreted as direct evidence in favour of the hypothesis. Some indirect evidence and possible ways for further testing of the hypothesis are also presented.

Dendrites↗
PubMedDate not supplied

[Theoretical volt-ampere input curve of a neuron with NC-dendrites after a uniform shift in clamped potential of the soma].

Dendritic membrane current-voltage curve (CVC) was estimated from motoneuron input CVC. The effect of the clamped potential shifting rate on NC-dendrite input CVC was analyzed. The influence of the membrane negative conductivity upon the input curve hysteresis was calculated. We propose the combined use of hysteresis and nonstationarity features of the negative resistance part of neuron input CVC for crucial experimental solution of ohmic or N-dendrite controversy.

Dendrites↗
PubMedDate not supplied

[Theoretical analysis of direct current field-induced polarization of ohmic neurons].

A theory for the DC field-induced polarization of arbitrarily branching dendrites is being suggested. Contributions of the dendrites and the axon to polarisation of the soma are estimated for a quasi-reconstructed turtle motoneuron. The polarization depends on the length constant monotonously and dose not depend on other electronic parameters. The measurement of the DC field-induced potential may be used for unique determination of the electrotonic structure of reconstructed cells, provided that a whole-cell recording is employed and the axons are unmyelinated, or truncated, or oriented across the field. Polarization of the distal dendrites is also being analyzed to get into insight into the phenomenon of the field-induced steady depolarization of the dendrites.

Animals↗
PubMedDate not supplied

[Theory of a cable with an irregular cross section].

We proposed an equation of 1D-cable with irregular and alternating shape of cross-section. This equation differs from an ordinary one for the regular cylinder by the generalized definition of electrotonic parameters. The theory is illustrated for the cable with elliptic and alternating sections. The described theory may be useful when defining electrotonic parameters from experimental values. The theory predicts that the commonly estimated values of electrotonic length constant might be higher and membrane's capacity (-)-lower than the real values. Electrotonic parameters (length constant, time constant, characteristic resistance) may be used more successfully than electric parameters of a biological cable (membrane and cytoplasm resistance, membrane capacity).

Dendrites↗
PubMedDate not supplied

[Theoretical analysis of the multistability of pyramidal neurons].

The two-step switch off the long duration Ca action potential was observed recently in neocortex pyramids [1]. The phenomenon was interpreted as an evidence of the N-type Ca-channel distribution in isolated loci [1]. We demonstrate here that the two-step switch off can be imitated in the model with even channel distribution in a reconstructed pyramidal neuron as well. The first high plateau of the action potential corresponds to steady polarization of the whole membrane. The first switch off of the high plateau to the second low plateau corresponds to the switch off of the steady depolarization of the short basal dendrites. The steady depolarization of the long apical dendrite is more stable thus the switch off of the low plateau is a consequence of the apical dendrite repolarization. The model includes N-channel inactivation and a somatic shunt. The shunt may be artifactual, due to implement, or natural, due to postspike hyperpolarization. Recent experiments [2] have proved that the Ca-channels are located everywhere in the pyramidal cell.

Action Potentials↗
PubMedDate not supplied

[EEG potential theory in a model with thin brain integuments. III. Source--tangential double layer in the cortex].

Estimates of EEG-potentials obtained in the model of polylayer spherical and flat cables indicate that the geometry of the skull has only little influence. Potentials of EEG of the radial dipole and the tangential double layer are expressed by simple formules in these models. A theoretical explanation concerning great dispersion of ECoG to EEG ratio and identity of EEG-potentials, registered by two electrodes spaced within about 2 cm of one another, is presented.

Electroencephalography↗