Biomedical subjects

B S Cheung

Publications and source records attributed to B S Cheung.

25 records · Page 2Linked to original sources

PubMed1990

Visually-induced tilt during parabolic flights.

A helmet-mounted visual display system was used to study visually induced sensations of self-motion (vection) about the roll, pitch and yaw axes under normal gravity condition (1g) and during the microgravity and hypergravity phases of parabolic flights aboard the NASA KC-135 aircraft. Under each gravity condition, the following parameters were investigated: (1) the subject's perceived body vertical with eyes closed and with eyes open gazing at a stationary random dot display; (2) the magnitude of sensations of body tilt with respect to the subjective vertical, while the subject viewed displays rotating about the roll, pitch and yaw axes; (3) the magnitude of vection; (4) latency of vection. All eleven subjects perceived a definite "up and down" orientation throughout the course of the flight. During the microgravity phase, the average magnitudes of perceived body tilt and self-motion increased significantly, and there was no significant difference in vection latency. These results show that there is a rapid onset of increased dependence on visual inputs for perception of self-orientation and self-motion in weightlessness, and a decreased dependence on otolithic and somatosensory graviceptive information. Anti-motion sickness drugs appear not to affect the parameters measured.

Aerospace Medicine↗

PubMed1990

Motion sickness susceptibility and aerobic fitness: a longitudinal study.

A longitudinal study evaluated the susceptibility to motion sickness in initially unfit subjects before and after an endurance training program. Motion stimulation was provided by the Precision Angular Mover, in which the subject was tumbled head over heels about an Earth-horizontal axis at 20 cycles per minute in darkness. Maximal aerobic power and the blood lactate response to submaximal exercise were evaluated with cycle ergometry. The training program caused significant improvements in VO2max and endurance capacity, and a significant decrease in percent body fat. There was a significant (p less than 0.0125) increase in motion sickness susceptibility after the physical training, suggesting that increased physical fitness caused increased susceptibility to motion sickness in some individuals.

Adrenocorticotropic Hormone↗

PubMed1987

An illusion of reversed direction in hyperopes.

If a subject who is sufficiently farsighted removes his corrective, positive, lenses and looks with one eye from a distance of one or a few meters, at a small lighted area such as the (continuously "on") indicator light of an electric toothbrush, razor, or smoke detector, and if a small object such as a pin is then moved slowly from above to below the subject's eyes (in a plane close to the eye), the subject will perceive the object moving normally from above to below until it encroaches on his view of the lighted area. The object will then be seen to encroach first on the bottom of the lighted area, and as the object continues to move down it will be seen to be moving up across the lighted area, exiting the lighted area at the top. Similarly, an object moved in front of the eye from the subject's left to his right will be seen by the subject to traverse the lighted area in the reverse direction, right to left, even though the subject moves the object himself. Also, while the object is in front of the lighted area, it is perceived as an upside down silhouette having surprisingly clear and sharp edges, and it appears to be located on the lighted area rather than close to the eye where it really is.

Form Perception↗

PubMed1983

Another function of the inner ear: facilitation of the emetic response to poisons.

If a foot were surgically removed and it was observed that walking was then impaired, it could be concluded that the foot is part of the normal mechanism for walking and that one of the physiological functions of the foot is to facilitate walking. In seven dogs, the vestibular apparatus of the inner ear was surgically removed and it was observed that the emetic response to certain poisons was impaired. It was concluded that the inner ear is part of the normal mechanism for vomiting in response to poisons, and that one of the physiological functions of the inner ear is to facilitate the emetic response to poisons. It seems likely that the mechanism, whereby the vestibular apparatus facilitates the emetic response to poisons, is the basis of motion sickness. In essence, motion sickness can be considered the result of activation, by motion, of a mechanism that normally functions to facilitate vomiting in response to poisons.

Animals↗

PubMed1982

An inexpensive surgical headholder for the rat.

In many surgical procedures, there is a need to secure the animal's skull in a particular orientation. Described here is a surgical headholder for the rat that is inexpensive and easily constructed. The main component of the headholder is a screw type tubing clamp that is modified to allow the hard palate of the rat to be rigidly secured to the base plate of the clamp. This headholder has proven to be a highly satisfactory alternative to commercially available devices.

Animals↗

PubMed1981

Motion sickness caused by rotations about Earth-horizontal and Earth-vertical axes.

Rotation at constant angular velocity about the head's Z-axis, with the rotational axis horizontal (barbecue-spit rotation), causes motion sickness and illusory perceptions of bodily movement. To determine whether such rotations about the head's X- and Y-axes cause similar effects, and to test the validity of the mismatch theory of motion sickness, more than 200 tests (using vertical axes as well as horizontal axes) were administered to 14 subjects. Three different visual conditions were also investigated: normal external vision, vision of only the inside walls of the rotating capsule, and eyes closed in the dark. In Earth-horizontal rotation, the X- and Y-axis stimuli were found to be equally as effective in provoking sickness as was the original Z-axis stimulus, and a comparable loss of perception of gravity occurred for all three stimuli. The horizontal axis stimuli were found to be very effective in producing sickness in all the three visual conditions, but the external vision condition was significantly less effective than the other two conditions. The findings were generally inconsistent with the mismatch theory.

Adult↗

PubMedDate not supplied

Circularvection about earth-horizontal axes in bilateral labyrinthine-defective subjects.

A stationary subject surrounded by a visual display rotating about an earth-horizontal axis typically experiences a sensation of continuous self-rotation (vection) coupled with a paradoxical sensation of a limited degree of body tilt, both opposite to the direction of the stimulus. The sensation of limited body tilt has been attributed to conflict between visually-induced vection, and otolithic and somatosensory graviceptive information which indicates that the body has not moved. We investigated circularvection and illusory body tilt about the horizontal axis in the pitch and roll planes in bilateral labyrinthine-defective (L-D) subjects. Results demonstrated that the bilateral group experienced complete unambiguous self-rotation through an upside-down orientation. The relative contributions of the otolithic and somatosensory graviceptors to visuall-induced tilt is discussed.

Adult↗