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Biomedical subjects

L N Kornilova

Publications and source records attributed to L N Kornilova.

At least 19 recordsLinked to original sources
PubMed2004

The role of gravitation-dependent systems in visual tracking.

The effects of prolonged microgravity conditions on the performance of visual tracking functions such as fixational rotations of the eyes (saccades), smooth tracking of linear and curved movements of a foveal point stimulus, and following a vertical pendulum-like movement of foveoretinal optokinetic stimuli were studied. Experiments were performed on 31 cosmonauts in freefall conditions, in ten cases followed by additional studies after a cycle of head movements and in 14 after resting. These experiments showed that while intrinsic visual functions were retained in microgravity conditions, there were decreases in the precision and speed measures of all types of visual tracking (fixational rotations of the eyes, smooth tracking) and, in some cases, complete degradation of the smooth tracking reflex, an increase in the time taken to fix the gaze on a target (by factors of 2 or more), and decreases in the frequency of stimulus tracking. During the initial period of adaptation to the altered gravitational conditions and periodically during prolonged flight, the system of smooth visual tracking was found to undergo a transition to a strategy of saccadic approximation, in which gaze tracks the movement of the target using a set of macro- or microsaccadic movements. These impairments, seen in virtually all the cosmonauts, resulted from vestibular deprivation (functional deafferentation of the otolith input) in conditions of weightlessness, while in cosmonauts conceptualizing space on the basis of perceiving the positions of the feet and head additionally showed support-tactile deprivation.

Adaptation, Physiological↗
PubMed2004

[Computer tests for research of the oculomotor reactions in patients with complains of dizziness].

New methodological principles for a study of vestibular function, intersensory interactions, and eye tracking function are proposed by parameters of spontaneous oculomotor responses and those induced by visual and vestibular stimuli using the series of computer stimulating programs, which provided polymodal, separate and combined stimulation of the visual and vestibular inputs for the OCULOSTIM unit. The method suggested allows to objectivity the subjective complaints of dizziness and equilibrium disturbances, to differentiate diagnosis of cerebral organic process and psychogenic disease of central nervous system (CNS), and to specify physiological systems involved in their pathogenesis as well as to diagnose subclinical cerebral vestibulopathy. Qualitative and quantitative characteristics of eye tracking movements with and without a visual background (retinal optokinetic stimulation) are the most informative in the differential diagnosis of organic and functional psychogenic CNS disturbances.

Diagnosis, Computer-Assisted↗
PubMed2004

[Betaserc treatment of psychogenic vertigo].

An effect of betaserc on the character and intensity of vertigo (V), psycho-autonomic state of patients, vestibular functions and oculomotor system, using computer stimulating programs, has been studied in 39 patients with V. After 4 weeks of the treatment, betaserc exerted a positive effect on patients; however, the optimal effect was shown in patients with psychogenic V (73%). In this group, betaserc reduced both V and other psycho-autonomic disturbances. After betaserc treatment, patients with psychogenic V demonstrated a normalization of the vestibular responsiveness parameters in 70% of the cases and of the parameters of spontaneous oculomotor activity and pursuit eye function in 40 to 90%.

Adult↗
PubMed2004

Velocity of head movements and sensory-motor adaptation during and after short spaceflight.

To investigate to time course of sensory-motor adaptation to microgravity, we tested spatially-directed voluntary head movements before, during and after short spaceflight. We also tested the re-adaptation of postural responses to sensory stimulation after space flight. The cosmonaut performed in microgravity six cycles of voluntary head rotation in pitch, roll and yaw directions. During the first days of weightlessness the angular velocity of head movements increased. Over the next days of microgravity the velocity of head movements gradually decreased. On landing day a significant decrease of head rotation velocity was observed compared to the head movement velocity before spaceflight. Re-adaptation to Earth condition measured by body sway on soft support showed similar time course, but re-adaptation measured by postural responses to vestibular galvanic stimulation was prolonged. These results showed that the angular velocity of aimed head movements of cosmonauts is a good indicator of sensory-motor adaptation in altered gravity conditions.

Adaptation, Physiological↗
PubMed2003

[Individual characteristics of correction of the cosmonauts' vegetative status with a method of adaptive biofeedback].

The ability of 4 cosmonauts to voluntarily control their physiological parameters during the standing test was evaluated following a series of the adaptive feedback (AF) training sessions. Vegetative status of the cosmonauts during voluntary "relaxation" and "straining" was different when compared with its indices determined before these sessions. In addition, there was a considerable individual variability in the intensity and direction of the AF effects, and the range of parameters responding to AF. It was GCR which was the easiest one for the AF control.

Adaptation, Physiological↗
PubMed2003

[Role of gravitation-dependent systems in visual tracing].

In 31 astronauts under conditions of free falling, when the visual functions proper were preserved, the precision and speedy parameters of all the forms of visual tracing (saccades, smooth tracing) became worse, and in a number of cases a complete disintegration of the smooth tracing reflex occurred as well as a 2-fold and greater enhancement of the time for fixing the stare at a target. In the beginning of adaptation to altered gravitation conditions, a transition of the smooth visual tracing into the strategy of saccadic approximation, occurs. These disorders were shown to be due to a vestibular deprivation.

Adaptation, Physiological↗
PubMed2001

[A tracking function of human eye in microgravity and during readaptation to earth's gravity].

The paper summarizes results of electro-oculography of all ways of visual tracking: fixative eye movements (saccades), smooth pursuit of linearly, pendulum-like and circularly moving point stimuli, pursuit of vertically moving foveoretinal optokinetic stimuli, and presents values of thresholds and amplification coefficients of the optokinetic nystagmus during tracking of linear movement of foveoretinal optokinetic stimuli. Investigations were performed aboard the Salyut and Mir space stations with participation of 31 cosmonauts of whom 27 made long-term (76 up to 438 day) and 4 made short-term (7 to 9 day) missions. It was shown that in space flight the saccadic structure within the tracking reaction does not change; yet, corrective movements (additional microsaccades to achieve tracking) appeared in 47% of observations at the onset and in 76% of observations on months 3 to 6 of space flight. After landing, the structure of vertical saccades was found altered in half the cosmonauts. No matter in or after flight, reverse nystagmus was present along with the gaze nystagmus during static saccades in 22% (7 cosmonauts) of the observations. Amplitude of tracking vertically, diagonally or circularly moving stimuli was significantly reduced as period on mission increased. Early in flight (40% of the cosmonauts) and shortly afterwards (21% of the cosmonauts) the structure of smooth tracking reaction was totally broken up, that is eye followed stimulus with micro- or macrosaccades. The structure of smooth eye tracking recovered on flight days 6-8 and on postflight days 3-4. However, in 46% of the cosmonauts on long-term missions the structure of smooth eye tracking was noted to be disturbed periodically, i.e. smooth tracking was replaced by saccadic.

Adult↗
PubMed2000

[Correction of autonomic reactions parameters in organism of cosmonaut with adaptive biocontrol method].

Presented are results of testing the method of adaptive biocontrol during preflight training of cosmonauts. Within the MIR-25 crew, a high level of controllability of the autonomous reactions was characteristic of Flight Commanders MIR-23 and MIR-25 and flight Engineer MIR-23, while Flight Engineer MIR-25 displayed a weak intricate dependence of these reactions on the depth of relaxation or strain.

Adaptation, Physiological↗
PubMed1997

Vestibular function and sensory interaction in altered gravity.

The effects of weightlessness on vestibular function have been studied since the beginning of manned spaceflight. The results of these studies have been highly variable and to some extent even contradictory, which makes it difficult to draw unambiguous conclusions. This variability is probably due to at least three factors: (1) individual differences in the adaptive process, (2) non-standardized experimental methods and conditions, (3) a lack of integrated experiments. For this reason, we have used a single integrated approach with a specially developed battery of tests. The results thus obtained for 21 cosmonauts on short- and long-term flights are reviewed here, and discussed in the light of the results obtained by others. Changes in the operation of the vestibular system and in all functions based on vestibular afferent input are commonly observed in spaceflight. These changes are characteristic for the process of adaptation and re-adaptation to altered gravity. They occur in a high proportion of persons exposed to such conditions, although there are individual differences with regard to severity, nature, time and duration of occurrence, and the dynamics of the process. Analysis of the observations in a large number of cosmonauts has permitted to distinguish three types of adaptation of the system to altered gravity. The first type of adaptation is characterized by a strong response to any stimulus during the initial adaptation period. The second type of adaptation is characterized by responses that are drastically decreased or even absent. The third type of adaptation is distinguished by the selective response of the sensory system to certain types of stimulation only. After long-term missions the process of re-adaptation usually takes a more severe course than the earlier process of adaptation to microgravity. Both adaptation and re-adaptation follow an undulating course, in which adaptation and re-adaptation are alternating. This is most conspicuous during long-term flights, and it suggests that in the initial stage of adaptation to weightlessness the vestibular input plays a dominant role, while at the end of the adaptation process the visual input prevails.

Eye Movements↗
PubMed1996

Phenomenology of spatial illusory reactions under conditions of weightlessness.

Sensory interaction and sensory adaptation in short- and long-lasting space flights (SF) and the dynamics of stability of adaptive shifts were studied by the phenomenology of spontaneous and visually induced illusory reactions. It was shown that perceptive impairment developed during the initial adaptation to microgravity should be considered regular reactions of sensory systems under given environmental conditions rather than special features of the individuals examined. The classification of spontaneous illusory reactions (SIR) under conditions of microgravity and the results of investigation of the vertical vection (vection is a visual illusion evoked by the optokinetic stimulation) are presented. The following previously unknown phenomena were registered for the first time: inversion of the vertical vection illusion (VVI) evoked by vertical and sinusoidal optokinetic stimulation, impairment of perception of the body schema during VVI, change in the character of VVI, and development of VVI asymmetry. During long-lasting existence under conditions of weightlessness the anomalous perceptive reactions continued to be registered episodically (the period of adaptation was replaced by that of deadaptation). A hypothesis was suggested for the possible mechanisms of the phenomena found. [Translated from Fiziologiya Cheloveka, vol. 21, no. 4, p. 50-62, July-August, 1995]

Adaptation, Physiological↗
PubMed1996

[Spontaneous and visually-induced oculomotor reactions in microgravity (Results of Austrian-Russian Experiment "Optovert" performed within the frame of program "Austromir", part II)].

Results of investigation of spontaneous and induced by vertical linear and sinusoid optokinetic stimulation oculomotor reactions in short- and long-term space missions are reported. Adaptation to microgravity was shown to be associated with rearrangement in sensory interactions even on a background of good subjective well-being and absence of abnormal autonomous nervous reactions. In the early period of adaptation to microgravity records were made of modified spontaneous oculomotor activity (spontaneous vertical nystagmus) and vertical optokinetic nystagmus (VOKN) including alterations in amplitude and VOKN amplification coefficient.

Adaptation, Ocular↗
PubMed1996

[Awareness of the subjective vertical in weightlessness (results of Austrian-Russian experiment Optovert performed within the framework of the program Austromir, part III)].

Data about intersensory interactions and adaptations, dynamics of the adaptive shifts were obtained in short- and long-term space missions basing on the indices of the subjective optical vertical awareness evaluated in experiment "OPTOVERT" with the use of dedicated ingenious techniques and hard- and software. As was shown, the function of subjective optical vertical (SOV) awareness remained unaltered in microgravity; however, in the period of adaptation there was a significant growth of error in SOV awareness in the darkness, and against the vertical optokinetic stimulation. In prolonged microgravity SOV error returns to the norm both in the darkness and during stimulation while arising asymmetry differs from background in magnitude and directivity, exceeds the physiological norm and sustains throughout a mission. After flight the asymmetry magnitude and directivity gradually regain the background values.

Adaptation, Physiological↗
PubMed1996

[Orientation illusions in weightlessness].

Results of the ANKETA and OPROSNIK experiments performed by 102 cosmonauts in and post flight were analysed. It is shown that perceptive disturbances (orientation illusions) developed in the period of early adaptation to weightlessness were not an inherent feature of individual persons but regular responses of the body sensory systems. The character, intensity, duration, and the dynamics of illusion responses in space mission are described. Forms of the vestibular disorders, types of adaptation of the sensory systems and classification of spontaneous illusion responses in the weightless environment are presented. Hypothesis for possible mechanisms of the illusion responses in weightlessness is suggested.

Adaptation, Psychological↗
PubMed1996

Microgravity effect on the vestibulo-ocular reflex is dependent on otolith and vision contributions.

BACKGROUND: We studied whether microgravity influences horizontal and vertical vestibulo-ocular reflex (VOR), and what the otolith contributes to VOR in the absence of gravity, in six cosmonauts during and after space missions. METHOD: VOR was elicited by active yaw and roll head movement at a frequency of about 0.2 Hz. RESULTS: The various individual quantitative changes (increase, decrease, and left-right asymmetry) found in the horizontal VOR evoked by yaw head movements during the adaptation period to microgravity suggested central reprogramming of mechanisms controlling VOR; i.e., a non-specific effect of microgravity on VOR. At the same time, horizontal and vertical VOR's were recorded during roll head movements, which were not obvious before flight. In the consmonaut who participated in a long-term flight, the increased activity of vertical canals turned to unidirectional (downward) eye movements, independent of the head movement direction, lasting during the whole mission. These VOR changes probably resulted from the absent adequate otolith stimulation and reduced otolith influence upon semicircular canal function. CONCLUSIONS: Thus, a specific effect of microgravity on VOR was observed during roll head movements, when the interaction between semicircular canals and otoliths should be more pronounced, mainly in the vertical plane. The stability of the "space" pattern of interactions in the readaptation period depended on the time spent in microgravity. We suggest that in visual-vestibular interactions revealed in VOR evoked by head movements with open eyes, vision dominates when a conflict arises between "space" and "terrestrial" patterns of sensory interactions.

Adaptation, Physiological↗
PubMed1995

[Neurophysiological patterns of vestibular adaptation to microgravity].

Results of the investigation of spontaneous and evoked by vestibular, ocular, and combined oculo-vestibular stimulation of the oculomotor reactions within space experiments Optokinesis and Labyrinth are presented. The experiments were carried out during the early adaptation to micro-g and repeated throughout long term mission. As was shown, the vestibular disturbances at the start of micro-g were not a lot of isolated individuals but regular reactions of the body sensory systems to the micro-g environment. Dynamic studies of the neurovestibular adaptive shifts in long-term microgravity allowed to register periodically evolving abnormal spontaneous and induced oculomotor reactions. Adaptation periods interchanged with the episodes of disadaptation. The periods of vestibular adaptation to microgravity and possible neural mechanisms of these events are presented.

Adaptation, Physiological↗
PubMed1995

[Spontaneous and visually induced illusory responses in weightlessness (results of the Austrian-Russian experiment "Optovert" performed within the framework of the program "Austromir", part I)].

There presented the results of studying the mechanisms of intersensory interactions and sensory adaptations, the dynamics of the stability of adaptive changes in the short- and long-term space missions by phenomenology of spontaneous and visually-induced illusory responses. It is shown that adaptation to microgravity even under good subjective health condition and the absence of anomalous subjective reactions was accompanied the change in the interaction of the sensory systems. For the first time there recorded the previously unknown phenomena: an inversion of vertical vection illusion (VVI) on vertical and sinusoidal optokinetic stimulation; disruption of the perception of body scheme at the instant of VVI; the change of character and the initiation of VVI asymmetry; the decrease of thresholds and the intensity increase of VVI. In the period of long-term stay in microgravity the anomalous perceptive reactions (the period of predominating adaptation gave way to the period of predominance of disadaptation). The hypothesis for the mechanisms of revealed changes was suggested.

Adaptation, Physiological↗
PubMed1993

Vestibular function and sensory interaction in space flight.

The vestibular system and vestibulo-visual interaction were examined in 11 astronauts by the electrooculographic (EOG) method during short- and long-term flights on days 2, 3, 5, 9, 22, 50, 164, and 169 (experiments OPTOKINES and LABYRINTH). In space (flight days 2 and 3), they showed enhanced spontaneous vertical nystagmus, and disorders of tracking of vertical and diagonal movements of the stimulus which improved after active head movements. Early increasing of the reactivity of the cupulo-endolymphatic system (flight days 2-3) was replaced after 5 days of flight with a reduction of the vestibular function and an increase of the significance of the visual input in the formation of oculomotor responses to combined vestibulo-optokinetic stimulation. The type of spontaneous ocular reaction and vestibular stimulation of oculomotor activity under the conditions of weightlessness represented, on one hand, the general responses of sensory systems to weightlessness and, on the other hand, specificity of integrating and adaptive processes.

Electrooculography↗