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Biomedical subjects

Iu K Stolbkov

Publications and source records attributed to Iu K Stolbkov.

At least 19 recordsLinked to original sources
PubMed2005

[Vestibular effects on posture instability evoked by moving visual environment and footing].

Subjects held the vertical posture standing up on hard footing, having small degree of the freedom in the frontal plane. The stability of the vertical posture has been assessed by the standard deviations (sigma) from average amplitudes of the fluctuations of the subject's head (in frontal and sagittal planes) from conditional zero. Sinusoidal rotations of optokinetic cylinder, sinusoidal rotations of the footing, and combinations of these rotations, under phase shifts between the optokinetic cylinder and the footing, caused increase of sigma. The amplitude and velocity signal of the head deviations was transformed into low galvanic current applied to the mastoids and used as the artifical vestibular biofeedback. It was possible to reduce the value of the sigma for lateral tilts (raised in comparison with their values during stance in the dark as a result of destabilizing influence), varying coefficients of the biofeedback. At the same time, appropriate fluctuations in sagittal plane were not systematic.

Adult↗
PubMed2003

[Habituation of horizontal eye nystagmus in pigeon during alternation of central and eccentric rotations].

Intact pigeons were rotated in the horizontal plane in the dark in different positions relatively to the rotation axis. At central rotations, the pigeon's head was in the rotation axis whereas at eccentric rotations it was displaced from the axis. Series of central and eccentric rotations were alternated. Each series consisted of 2-5 rotations using angular velocity trapezoids. All stimuli producing habituation were used at most 14 times each. Eccentric rotations did not prevent a gradual decrease of peak velocities of the slow component of primary nystagmus on transition from one series of central rotations to another in 17 pigeons (group 1). The increase of peak velocities was observed in 2 pigeons (group 2). In group 1, a direct dependence among alterations of this parameter of primary nystagmus, modifications of its duration, and variations of peak velocities of secondary nystagmus, were observed. If two identical stimuli did not follow in sequence directly, the effect of the second one produced same nystagmus changes as were observed in present pigeon by comparison of the first and last responses in the series of the central rotations. If they follow one by one, in many cases the second stimulus in the pair produced an increase of peak velocity of primary and secondary nystagmus and rise of delay of the point of primary nustagmus peak velocity. These variations were not random (probability, > 95%).

Animals↗
PubMed2000

[Mechanisms of the otolith signal processing].

A series of current hypotheses of mechanisms of the otolith signals processing and organization of adaptive responses of the oculomotor system to gravito-sensitive (otolith) inputs are reviewed: the "frequency segregation of the otolith signals", "gravito-inertial force resolution", "spatio-temporal transformation of the angular vestibulo-ocular reflex", "inertial processing of the vestibular signals", "asymmetry of the otolith signals", and their experimental corroboration.

Animals↗
PubMed1998

[Interaction of the angular and linear components of the horizontal vestibulo-ocular reflex in the pigeon].

Pigeons were exposed to centric and eccentric horizontal rotations in darkness by velocity trapezoid. Different in sign the duration alterations of the opposite directed horizontal eye nystagmus occurred during otolith membrane shifts in sagittal as well as frontal planes. A direct dependence was found between the duration alterations of the primary nystagmus phase and the peak value alterations of its slow phase velocity under increased (but not decreased) centrifugal force. In the both cases, if duration of the primary nystagmus phase was enlarged, duration of its secondary phase was diminished and vice versa. It suggests the otolith component does not decay up to zero by constant velocity and at once after rotation; by deceleration it is biphasic. In affirms the own hypothesis that the linear component is asymmetric central neuronal activity that modifies the canal component even if this activity by itself is not enough for eye movement initiation.

Animals↗
PubMed1998

[Fragmental regulation of vestibuloocular responses].

Intact pigeons were exposes to whole body centric and eccentric horizontal rotations in darkness during angular velocity trapezoids. The overall nystagmus alteration patterns were analysed. In 10 pigeons, all nystagmus alterations may be explained on the basis of the dynamics of peripheral otolith activity and central effects that are the same for all combinations of interacting inputs (type 1 patterns), whereas in other pigeons part of the nystagmus alterations were connected with some central effects that were individually specific and touch upon the responses to separate combinations of interacting input (type 2 patterns). It was observed the transformation of type 2 to type 1-patterns during the reiterated rotational trails and light nembutal anesthesia. A fragmentary control of the vestibulo-ocular responses seems to exist. This implies that the CNS is able to discern numerous kinds of bilaterally organized interacting inputs arising during different otolith membrane shifts.

Animals↗
PubMed1994

[The interaction of vestibular inputs with differing orientations of the otoliths in a gravitational field].

In alert pigeons Columba livia effects of static tilts about fore-aft and binaural axes (angles of tilts: 30-40 deg) on neck and ocular nystagmus elicited by monaural galvanic stimulation of the lateral semicircular canals with sinusoidal currents (peak amplitudes: 20-100 microA; period: 35 sec) were investigated. It was shown that the same angles of the tilts elicited different changes of horizontal nystagmus parameters in different animals. In some of them changes of quantitative characteristics of opposite-directed nystagmus differed with signs. Data support the correctness of recently (Stolbkov, 1989) proposed scheme of forming vestibulomotor reactions, according to which signals from heterolateral vestibular nuclei, during nystagmus, which are integrated, contain both canal and otolith components independent of stimulus mode addressed to canals or otoliths (separately or jointly). Results suggest also that caloric test may be a source of incorrect conclusions concerning state of vestibular system during static tilts the responses of functionally asymmetric semicircular canals may be symmetric ones. Moreover data suggest that sensitivity of convergent vestibular neurons to the canal signals is different depending on separated or combined canal and otolith stimulations.

Animals↗
PubMed1990

[Interlabyrinthine otolithic symmetry and asymmetry as factors in canal-otolith interaction].

The intact and operated (unilateral cutting of utricular or saccular nerve branches) pigeons were exposed to rotations in the horizontal plane. The position of the pigeon with respect to the rotation axis was such that horizontal canal afferents were activated either separately or together with otolith afferents. The results of canal-otolith interaction did not depend directly on enhancement or diminishing of the otolith afferentation but rather on a relative amount of the otolith signal alterations from the two labyrinths. Any variations of the nystagmus duration (increasing or decreasing) could result from different changes of the otolith signals from the two labyrinths.

Acceleration↗
PubMed1989

[Canal-otolithic interaction under conditions of otolithic asymmetry].

Intact pigeons were exposed to horizontal rotations so that the horizontal canal afferents were activated either separately or simultaneously with macular afferents. When the pigeons, head was off the axis of rotation, the radial acceleration (0.5 g) acted either in sagittal or in frontal plane. In presence of otolith asymmetry, the radial acceleration modified the rotation-induced nystagmus depending on the direction: the duration of the rightward nystagmus was increased whereas the duration of the leftward nystagmus was decreased, and vice versa. These changes occurred irrespective of the source of the otolith asymmetries. Theoretical significance of this data is discussed and possible mechanisms of the canal-otolith interaction are considered.

Acceleration↗
PubMed1977

[Participation of vertical semicircular canals in the vestibulo-oculomotor response to the horizontal rotation test].

The horizontal rotatory test was shown to elicit in rabbits a complex three-plane vestibular oculomotor response with rotatory nystagmus (RN) in sagittal plane. The leftward accelerating rotation caused the clockwise RN of the right eye; during decelerating rotation the RN was directed counterclockwise. Its frequency may differ from that of the horizontal nystagmus. The cupulo-endolymphatic displacements seem to occur not only in the horizontal canal, i.e. in the plane of rotation, but also in the vertical canals as a result of a hypothetical hydrodynamic interaction between the canals. The displacements in the anterior and the horizontal canals of the labyrinth were analogous, whereas that in the posterior canal was of the opposite direction. That suggests that the utriculofugal displacements in the horizontal and the anterior canals are accompanied by an utriculofugal displacement in the posterior canal, and vice versa.

Animals↗
PubMed1976

[Changes in nystagmus following otolith stimulation].

In rabbits, stimulation of the otolith organs was shown to exert a double effect on nystagmus evokedby adequate stimulation of semicircular canals' receptors: The immediate and the delayed. On simultaneous stimulation of the two portions of vestibular apparatus, inhibition of systagmus occurs. In the course of aftereffect of the otolith stimulation, both the activated and the inhibited responses as well as the responses similar to control can be revealed, depending on the time interval between presentationsof otolith and cupulous stimuli.

Animals↗
PubMed1975

[The vertical and rotatory components of ocular nystagmus induced by rotation in a horizontal plane].

During rotation of the rabbit around a vertical axis, movements of the eye were recorded on film. The rotation test involved positive angular accelaration (10 grade. sec(-2)), two-minute rotation with constant angular speed (166 grade. sec(-1)), and negative angular acceleration (10 grade. sec(-2)). Two variants of rotation were used: in one of them the rotation axis passed between labyrinths, in another - an excentricitet providing centrifugal force of 0.5 g was present. The successive processing of the film revealed simultaneous movements of the eye in three planes: horizontal, frontal, and sagittal. The movements in all the planes consisted of rhythmic (hystagmal proper) and tonic components. The movements in sagittal and frontal planes were comparable with those in horizontal planes. A tonic otolith reflex occurred additionally at the excentric rotation. The complex form of the nystagmus is regarded as a result of hydromechanical interaction between semicircular canals.

Animals↗