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Biomedical subjects

J Wetzig

Publications and source records attributed to J Wetzig.

5 recordsLinked to original sources
PubMed1993

Oculovestibular interactions under microgravity.

On a space mission in March 1992 a set of experiments were performed aimed at clarifying the interaction between visual, proprioceptive and vestibular inputs to the equilibrium system. Using the VESTA goggle facility from the European Space Agency we investigated the effect of pure neck receptor stimulation on eye position as measured by the flash afterimage method and on perception of a head-fixed luminous line in space. Space vestibular adaptation processes were measured by rotating pattern perception during prescribed head movements. It was found that static ocular counterrotation does not occur under microgravity conditions. This result suggests that the neck receptors apparently do not contribute to a measurable extent. The subjective orientation of a vertical line was perceived correctly inflight. Obviously neck receptors on the perception level can fully substitute for the ineffective equilibrium organs of the inner ear within less than 4 days. The rotating pattern perception during different head motion patterns is not influenced by the absence of a gravity reference.

Adaptation, Physiological↗
PubMed1993

Responses to eccentric rotation in two space-bound subjects.

Two subjects were rotated eccentrically in the manner described previously. In contrast to a normal control group, settings of a luminous line to the subjective vertical were almost unrelated to the gravitoinertial vector before, and totally so shortly after, space flight. Only 3 days postflight did a clear relation to the gravitoinertial vector re-establish itself in the one subject who actually flew. The correspondence became normal 5 days after the flight. Since there were no clinical abnormalities evident in the subjects, it is suggested that both subjects suppressed their vestibular information, presumably as an effect of vestibular deconditioning training before the flight. In addition, as a consequence of the flight experience one subject continued to ignore it several days after the flight.

Humans↗
PubMed1991

Influence of gravity vector on eye movement elicited by linear acceleration.

When the body/head motion is sensed by otolith organs, they respond not only to the resultant acceleration of the motion but also to the gravitational force. We investigated the influence of the gravity vector on the otolithic-ocular reflex caused by motion in normal subjects. The sled type linear accelerator, moving back and forth with a frequency of 0.25 Hz and an amplitude of 2 m, generated right-left linear acceleration with a maximum magnitude of 0.5 g. We tested every subject under seven different postures: 1) 135 degrees forward tilted (F.T.), 2) 90 degrees F.T., 3) 45 degrees F.T., 4) upright sitting, 5) 45 degrees backward tilted (B.T.), 6) 90 degrees B.T., and 7) 135 degrees B.T. Horizontal eye movements with nystagmic pattern were elicited by these stimulations and were recorded by EOG. The eye movement data were analyzed by using a computer with the following procedure. After extraction of saccadic components from the data, the remaining parts were connected smoothly. The waves reconstructed in this manner, considered to be primary otolithic-ocular responses, were processed with the FFT method for calculating the amplitude of the component at 0.25 Hz. As a result, the responses were larger in the forward tilted postures than in the backward tilted postures.

Acceleration↗
PubMed1987

Rotation speed of labyrinthectomized fish during short-duration weightlessness.

This study used blind unilaterally labyrinthectomized goldfish of 5 to 15 cm body length. These goldfish were flown in parabolic flights to temporarily effect the loss of the second vestibular apparatus. Flights took place between 1 and 72 h after the operation. Attitude in 3 axes was recorded on video and analyzed from single-frame pictures for speed and direction of rotation about the roll (fish's body longitudinal) axis. Labyrinthectomy resulted in a rotation pattern consistent with literature under normal Earth-G conditions. Under diminished G-influence, the rotations, contrary to our expectation, did not stop, but, rather, increased in speed by a factor of 2 to 4. The direction of rotation did not change. The fish readapted to the low-G environment rapidly and returned to the rotation speeds observed before entry into the parabolas during the 5 to 7 s of parabola duration. Current theories for the generation of adaptation are discussed and their merits in explaining the experimental data are compared.

Adaptation, Physiological↗