[Changes in rigidity of the internal ear in body tilt].

We tried to select information concerning changes in acoustic rigidity of the internal ear in 90% body tilt from tympanogram. In such conditions there is no correlation between a 10-fold rise of perilymph pressure and tympanogram parameters. This contradiction suggests that rigidity of tympanogram is a total of rigidity of the ear canal part, middle and internal ear; that inert rigidity of the middle ear in body tilt masks a weak dynamic component of the internal ear. Determination and isolation of the ear canal rigidity from tympanogram (compensation) is a standard procedure. For compensation of the dominating static component of the middle ear we used an original technique -- deduction of the numbered tympanograms. We estimated that deduction of the initial position tympanogram from subsequent tympanograms yields the dynamic component. The procedure of deduction for the tilt angles +75, 60, 45, 30, 15, O, -15 and -30 produced transformed tympanograms (TT) the rigidity of which was 7-10 times less that peak rigidity of standard tympanograms. Peak rigidity of TT of 5 volunteers (n=8) changed as the function of a tilt angle and significantly differed in different positions. TT rigidity may be formed by peripheral cochlear membranes.

[The impact of long-term isolation on visual acuity]. / Vliianie dlitel'noi izoliatsii na ostrotu zreniia.

During the experiment with 90- and 7-day isolation and confinement tests were applied to evaluate, along with static, expositional and dynamic (DVA) visual acuity using automated system VZGLIAD (Gaze). Test distance was 1 meter. To assess DVA, the subjects were requested to make oscillatory movements with the head in the horizontal plane with a metronome frequency at 1 Hz. An upward trend in static visual acuity was interpreted as a result of myopization engendered by exposure to confinement and video display. A significant loss in expositional (and dynamic) visual acuity was stated in the main (p > 0.01) and visiting (p > 0.1) crews. These shifts could be associated with the dominance of inhibitory processes in the visual cortex due to monotony of the visual environment and insufficient oculomotor and accommodative activities.

[The perception of direction during counterrotation of the head and trunk]. / Vospriiatie napravleniia pri protivovrashchenii golovy i tulovishcha.

Investigations of perception of the "straight forward" direction and a visual target have been carried out with the use of a unique test facility providing negative feedback between horizontal rotations of the head and the chair. Administration of tests with visible or screened hand demonstrated a deviation of subjective axis "straight forward" from the body median by 13 degrees during synchronous but diversely directed rotations of the head and the chair. Under the same test conditions hand movements towards the target were highly precise. The results show a weak interrelation of egocentric head and body directions.

[Effect of a combination of head-down posture and LBNP on human tracking performance and spatial orientation]. / Issledovanie vliianiia kombinatsii antiortostaticheskogo polozheniia i ODNT na kachestvo slezheniia i prostranstvennuiu orientirovku cheloveka.

Test subjects exposed to a head-down tilt at--30 degrees for an hour participated in the experiment. The use of LBNP during tilting improved precision of arrow orientation on the round-shaped screen (during continuous tracking) but did not influence orientation relative to the gravitational axis and the long axis of the body. The selective effect of LBNP on the orientation can be attributed to the increased importance of inner coordinates due to the pressure of interior walls of the LBNP suit on the foot surface, and blood pooling in the dependent part of the body.

[Oriented rat movement in a rotating system]. / Orientirovannoe peredvizhenie krys vo vrashchaiushchiesia sisteme

In experiments with rotating of rats, their avoidance responce was studied: rats moved into the central portion. The 7 degrees or 15 degrees pitch of the central portion's walls caused significant moving of rats towards a square peripheral portion. When experimenting in darkness, the moving--towards--center response was restored, while under illumination the preference of the peripheral portion was again revealed in the rats obtained are are regarded as confirming the hypothesis of taht the moving--to center response during rotation is due to discrepancy between the vestibular and the visual systems of coordinates in peripheral portions of centrifuge.

Study of space perception functioning during simulation of certain space flight factors.

The results are reported of spatial perception function studies in 130 healthy males of 17-35 years of age and in 33 people with complete or partial inhibition of the function of the labyrinth (deaf-mutes). The comparative magnitudes of gravitational vertical perception impairments were studied during vestibular stimulation (Coriolis and linear acceleration), as well as during clino-orthostatic and antiorthostatic hypokinesia. Hypokinesia to a certain extent permitted the simulation of the blood redistribution in weightlessness. The ability of the subjects to determine the subjective visual vertical was used as the test criterion. The experiments have shown that the magnitude of the observed changes in the human sensory area depends on the physical properties of the vestibular stimulus, on the angle of inclination of the head of the bed during hypokinesia and on the duration of bed rest, but not necessarily on the level of vestibular tolerance. Possible mechanisms of impairment of perception in the space flight environment are discussed. Examinations of spatial perception function are useful during selection procedures for astronauts and airmen.

[Perception of 2-dimensional space coordinates during prolonged experimental hypokinesia]. / Vospriiatie koordinat dvukhmernogo prostranstva pri dlitel'noi éksperimental'noi gipokinezii

The effect of a 30-day hypokinesia on the perception of the subjective optic vertical (SOV) was studied. The test subjects who were in the antiorthostatic position (at an angle of 96 degrees to the vertical) showed the greatest changes in the SOV perception and illusive perception of the spatial position of the body. During the first two days of the experiment and ten days after it they displayed a 1.5-fold increase in the error of the SOV perception. In addition, they exhibited an asymmetrical perception of the SOV on the right and left side. In all cases the direction of the SOV displacement from the true line coincided with the body position. The test subjects who were kept at an angle of 84 degrees to the vertical (orthostatic hypokinesia) demonstrated only illusions of the body position during the first hypokinetic day and a unilateral increase in the error of the SOV perception after the experiment. The test subjects who underwent preventive treatment following antiorthostatic hypokinesia (at an angle of 94 degrees to the vertical) exhibited no asymmetry and an insignificant error in the SOV perception. These findings are discussed with regards to the changes in the function of pressuretension receptors and disorders in the skeletal tone during hypokinesia.