Visual fields for frontal plane motion and for changing size.

Thresholds were measured in 15 subjects for 2-Hz oscillations of size and for 2-Hz oscillatory motion in the frontal plane using test squares of side lengths 0.5 degrees, 1.0 degrees and 2.0 degrees. Size-oscillation thresholds were lowest (i.e. sensitivity was greatest) for the 2.0 degrees square while thresholds were highest (i.e. sensitivity was least) for the 0.5 degrees square in 28 of 34 tests. Frontal plane motion thresholds, on the other hand, did not generally depend on square size. Equal-threshold contours in the visual field were roughly elliptical in 10 of 13 subjects for both types of oscillation. None of 13 subjects had visual field defects for oscillating-size or frontal plane motion, in contrast with the known incidence of stereo-motion scotomata. One subject was known to be selectively "blind" to stereoscopically-oscillating disparity in some areas of the visual field, but oscillating-size sensitivity was normal in these regions, thus preserving an alternative basis for motion-in-depth judgments.