Effects on Visual Acuity and Stereoacuity of Oculomotor Changes Produced by Pre-Flight Adaptation Training
Fig. 1. An illustration of the motion profile of the visual surround (inside of the box) and the subject platform (thick line) during TTD stimulation. The visual surround translates on the platform while the platform tilts, allowing the programming of complex visual-vestibular motion profiles. In the left panel, the downward vertical arrow indicates that the rear of the platform is beginning to tilt downward. At the same time, the visual surround is beginning to move toward the subject as indicated by the rightward horizontal arrow. The right panel shows the other half of the cycle, in which the front of the platform begins to tilt downward and the visual surround moves away from the subject. In our experiments, motion of both the platform and visual surround are sinusoidal with a frequency of 0.12 Hz. The amplitude of platform tilt is ±4 deg, with a 4 deg rearward offset, such that the tilt is 8 deg backward and returns to level/horizontal. The amplitude of surround motion is 1.5 m. The phase between tilt and surround motion is 270 deg, such that when the surround is at maximum velocity moving toward the subject, the subject is at maximum tilt backward.
Fig. 2. Difference between stereothresholds before and after TTD adaptation of 30 and 60 minutes for two subjects. Data for upward and downward gaze shifts are averaged. The disparity used in the TT method was 4 arc-min. The error bars for subject S1 represent one standard error.
Fig. 3. Vernier thresholds during gaze shifts involving only eye movements (inside) and eye-plus-head movements (outside) are plotted for targets in four directions of gaze. The data are the average of five subjects. The error bars represent standard errors.
Fig. 4. Average Vernier thresholds for vertically separated dot and irregular shape targets. The gap is the center-to-center distance between the two targets that comprise the Vernier stimulus. Different symbols represent thresholds for targets of different area, in square arc-min. The error bars represent standard errors.
Fig. 5. Motion thresholds as a function of target velocity during pursuit of smooth and sampled horizontal motion of the entire target. The target was a 1 deg x 1 deg cosine grating of 2.3 cpd at 50 percent contrast. Motion thresholds were measured as the minimum phase shift between two temporally alternating (100 ms per frame) cosine gratings necessary to perceive vertical or horizontal motion of the grating bars. (a.) Vertical motion thresholds (phase angle - pdeg) during pursuit tracking of sampled target motion. The amplitude of each motion step was either 0.02 or 0.16 deg. The thick line through the black triangles shows average thresholds for three subjects. (b.) Horizontal motion thresholds (phase angle) during sampled pursuit tracking. The amplitude of each motion step was either 0.02 or 0.16 deg, as in panel (a.) However, note the different vertical scale from panel (a.) (c.) Vertical motion thresholds (phase angle) during pursuit tracking of smooth target motion. The amplitude of each motion step was vanishingly small. The vertical scale is identical to that in panel (a.).
Fig. 6. Thresholds for vertical motion at various frequencies of horizontal oscillatory head motion. The targets used in this experiment were the same as those in the pursuit tracking experiments. In this experiment, the grating patch was physically stationary and motion thresholds were determined while the subject moved his or her head voluntarily in synchrony with a metronome. The amplitude of head motion was approximately ±15 deg.
Contents
ISSO -- Institute for Space Systems Operations
1997-1998 Annual Report
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