PubMed Health⌕ Search

Biomedical subjects

M M Levashov

Publications and source records attributed to M M Levashov.

23 records · Page 2Linked to original sources
PubMedDate not supplied

[Model of the formation of nystagmic reactions to a set of caloric tests].

The model can furnish additional information about the vestibulary system, when evaluating caloric tests. The model has been built with certain assumptions being made. The nystagmus intensity (the slow component rate during maximum intensity) is assumed to be proportional to the difference between energy levels (EL) of the right and left vestibular nuclear complexes (NC). El of each NC is equal to the afferent flow (AF) plus its inherent activity (IA). During caloric (two warm and two cold) tests IA remains constant. AF at rest is equal to spontaneous activity of receptors and during stimulation it increases or decreases in a linear fashion. Parameters of the model are: difference between intensities of reactions to warm and cold tests, difference between EL of two (right and left) unstimulated NC, and ratio of nystagmus intensity to the stimulus for each labyrinth. The behavior of the model during vestibular dysfunctions of various origin (changes in one of AF characteristics or changes in IA of one NC) is discussed. The diagnostic application of the model is illustrated by the discussion of nystagmometric data. The conclusion about vestibular dysfunction and its etiology can be made on the basis of statistic analysis of parameters of the model in the norm.

Caloric Tests↗
PubMedDate not supplied

[Opto-vestibular interaction based on nystagmometric data].

Nystagmograms recorded in healthy people (270 ENG from 30 children, aged 3 to 7) were analyzed quantitatively. The velocity of the slow component of the vestibular nystagmus during caloric tests, optokinetic nystagmus in response to stimuli applied at 20 and 10 degrees/sec, as well as vestibulo-optokinetic nystagmus resulting due to the inhibitory or enhancing effect of caloric stimulation were measured. The modulation level, i.e. the change of the velocity of the slow component that accompanied the transition of the optokinetic nystagmus to the vestibulo-optokinetic nystagmus, was always less than that of the vestibular nystagmus. This disagrees with the concept about algebraic summation of intensities of the reactions. The modulation level showed a low correlation with the vestibular nystagmus slow component velocity and depended on the optokinetic nystagmus velocity: at 10 degrees/sec the inhibitory effect was smaller than the enhancing one and at 20 degrees/sec the situation was the opposite. At 20 degrees/sec the slow component velocity was twice higher than at 10 degrees/sec. It is therefore suggested that the parameter reflects the level of the residual activity of the optokinetic system which is independent of vestibular afferentation.

Caloric Tests↗