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Biomedical subjects

V S Gurfinkel'

Publications and source records attributed to V S Gurfinkel'.

At least 19 recordsLinked to original sources
PubMed1999

[Errors in targeted movements of the hand under the conditions of orbital space flight].

Three crew members of the Russian-French MIR mission were tested to determine errors in pointing to memorized visual targets. In the laboratory, all test-subjects consistently used to point to the spot below the actual target presentation. The mean Y-error (the vertical error) made up -31.6 +/- 21.8 mm. In microgravity, the Y-error moved "upward" so that the mean Y-error was -16.8 +/- 37.0 mm. The data demonstrate adaptation of the central program of aiming arm movement to the microgravity conditions.

Adaptation, Physiological↗
PubMed1995

[Study of the microgravity effect on the inertia of mental tracking of moving objects].

Effect of microgravity on operator's ability to mentally track moving objects was investigated during the joint Russian-French space mission in 1992 and the subsequent 6 month Russian mission. Subject was to track a sequence of 4 frames in which 3 points were changing their locations in the manner as if they were moving linearly at a constant speed; after that the subject was to compare the last frame of the sequence with a new, 5th frame in which the points either had the same locations or slightly shifted on the preceding pattern or in opposite direction. Shifting of the points at which their locations in two last frames seemed to be identical was evaluated. The investigation infers that microgravity does not exert any significant influence on the inertia of mental tracking of moving object or there occurs rather quick, within a period of days, adaptation to a new situation.

Adaptation, Physiological↗
PubMed1992

[Switching effect in the system of equilibrium regulation in man].

Postural reactions evoked in human by bilateral vibration of calf muscles were studied under different conditions: sitting without the feet contact with a support; sitting in an unstable position on the edge of the chair; sitting under conditions of the foot contact with different types of supports (rotating disk, suspended platform, etc.); standing with an asymmetrical load applied to the trunk. It has been shown that local vibration of calf muscles can evoke activation not only of the vibrated muscle or of its antagonist (local effects), but also of extensors and flexors of the knee joint (non-local effects), or of the remote muscular groups, involved in different postural synergies. The concrete pattern of muscle activation is determined by several factors, the most important being the relative position of the body links and interaction of feet with a support. The mental image of the body configuration in the system of internal representation is also very significant.

Humans↗
PubMed1989

[Immediate and remote postactivation effects in the human motor system].

Postactivation effects (appearance of long-lasting non-voluntary contraction of muscles after 30-60 s of the sustained voluntary effort) were studied. It is shown that after contraction of distal muscles postactivation effects can appear in proximal muscles not involved in the previous voluntary activity. The testing of the motor system state by the muscle tendon vibration revealed that besides the well known immediate postactivation effects there were concealed changes lasting for 15-20 min. It is suggested that postactivation phenomena reflecting the functioning of certain central tonogenic structures activated by a voluntary effort or by an increased afferent inflow can be used as an efficient tool in the study of postural mechanisms.

Electromyography↗
PubMed1989

[Changes in the direction of vestibulomotor responses in the process of adaptation to prolonged static head turning in man].

Vestibulomotor responses were studied in normal blindfold subjects in the upright posture during adaptation to maintaining the head turned to the left up to the extreme position for 10 min. The head was maintained in that position either passively or actively. In 5 out of 12 subjects tested, adaptation to the unusual head position resulted in a gradual decrease of the appreciated angle of the head position. The error in appreciating the head position reached as much as 70-80 degrees. The direction of the vestibulomotor response was found to change in parallel with the appreciated head orientation. Thus, under mismatch between the perceived and actual head positions the direction of the vestibulomotor response corresponded to the spatial perception rather than to the actual head orientation.

Adaptation, Physiological↗
PubMed1988

[Effect of real and illusory movements on the human vestibulomotor reaction].

Lateral stabilographic responses to galvanic labyrinth stimulation were studied in healthy subjects in the standing posture. The responses increased during the body tilt forward performed either voluntarily or involuntarily as a result of vibration of the tibialis anterior muscles. The illusory body tilt forward induced by the vibration of the triceps surae muscles under mechanical fixation of the trunk resulted in similar increase of the vestibulomotor response. It is concluded that the enhancement of the vestibulomotor responses during voluntary movements is mediated by the spatial perception system.

Adult↗
PubMed1988

[Participation of the secondary motor area of the frontal lobe of the brain in organizing postural components of human voluntary movement].

Synergies of the orthograde posture associated with voluntary movements (deep respiration or fast arm elevation) were studied in 225 patients with local verified brain lesions. Postural adjustments associated with deep respiratory movements were disturbed in patients with lesions of mainly posterior part of the inferior convolution of the frontal lobe. Postural adjustments associated with arm elevation were disturbed in patients with lesions of mainly the posterior part of the superior frontal convolution corresponding to the supplementary motor area. It is concluded that postural components of different voluntary movements requiring learning are controlled by different secondary motor areas.

Arm↗
PubMed1986

[Spatial perception and vestibulomotor reactions in man].

Postural responses to transcutaneous galvanic stimulation of the right labyrinth were recorded by means of a stabilograph in normal human subjects in various head positions as well as under the illusion of head and trunk rotation induced by vibration of the gluteus maximum muscle. The direction of the vestibulo-motor response was determined by the position of the head: in a normal head position the body swayed in the frontal plane, whereas with the head turned 90 degrees it moved in the sagittal plane. During the illusory head and trunk 90 degrees rotation the responses were sagittally directed like those recorded in the real head-turned-sideways position. When the vibration did not induce the illusion of the head rotation with respect to the feet, the direction of the postural response was determined by the real head orientation. It is concluded that the spatial perception system is involved in the control of spatially oriented vestibulo-motor responses.

Adult↗