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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
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↗
PubMedDate not supplied

[Vestibular nystagmus as a result of the interactions between semicircular canals and the otolithic membrane subsystems of the vestibular system].

Untreated and treated (unilateral section of utricular and saccular branches of the vestibular nerve) pigeons Columba livia were rotated in the dark in the horizontal plane, the head being in a different position relative to the axis of rotation. The range of angular acceleration was 7-19 deg/c2 and the peak value of centrifugal acceleration was 0.5 g. The neck and eye nystagmus was recorded. It was found that: 1) the result of canal-otolith interaction was not directly related to the pattern of changes of otolith afferentation but was determined by the ratio of otolith afferent signals in the right and left labyrinths and, consequently, by the ratio of patterns of activities in the CNS paired structures that receive otolith afferentation; 2) the same result of interaction (enhancement or attenuation of vestibular responses) can be achieved through both increase or decrease of otolith afferentation; 3) if joint stimulation of semicircular canals and otolith organs induces asymmetry of neuronal activities of paired brain structures that perceive otolith afferentation, then, irrespective of the mechanism of origin of this asymmetry, it is followed by changes of oppositely directed nystagmus of different sign (increase for one nystagmus and decrease for the other). It is concluded that the symmetry of reactions recorded in response to isolated stimulation of semicircular canals (otolith organs) cannot be considered as a reliable criterion of functional symmetry of semicircular canals (otolith organs).

Animals↗
PubMedDate not supplied

[Nystagmus in subjects exposed to asymmetric changes in otolith afferents].

Patients with unilateral cochleo-vestibular disorders (23 patients) were rotated in the dark about the horizontal plane with their head positioned differently in relation to the rotation axis; central position (the rotation axis lies between the centrifugal force of 0.5 G acted either in the occipital-frontal direction or in the frontal-occipital direction. In each position a pair of oppositely directed nystagmus was recorded. These nystagmus pairs recorded at different levels of otolith activities were compared. In 19 patients, otolith asymmetry symptoms were observed: in them at least one of the changes of otolith activities was accompanied by an increase of the nystagmus duration of one direction and a decrease of the nystagmus duration of the opposite direction. In 10 patients, changes observed were similar to those detected in pigeons with peripheral otolith asymmetry: alteration of the centrifugal force direction in these patients changed the sign of nystagmus shifts (duration of nystagmus that increased during rotation in one of the off-axis positions diminished during rotation in the other position and vice versa); changes of the nystagmus that occurred when the centrifugal force increased differed in sign from those that occurred when the centrifugal force decreased.

Adolescent↗
PubMedDate not supplied

[Relationship between nystagmus and utricular function].

The horizontal neck nystagmus arising in response to angular acceleration was recorded electromyographically in pigeons (Columba livia). After bilateral section of the utricular nerves (Roumuli utriculi) the nystagmic reactions to the right and to the left remained symmetrical although they were delayed when compared to the reactions of intact animals. Unilateral section of the utricular nerves caused asymmetric reactions from the semicircular canals: the nystagmus toward the dissected nerve was delayed to a greater extent than that toward the intact nerve.

Acceleration↗