Foreground and background in dynamic spatial orientation

Abstract

The dependency of visually induced self-motion sensation upon the density of moving contrasts as well as upon additional stationary contrasts in the foreground or background was investigated. Using two different optokinetic stimuli, a disk rotating in the frontoparallel plane, and the projection of horizontally moving stripes onto a cylindrical screen, it was found that: (1) visually induced self-motion depends upon the density of moving contrasts randomly distributed within the visual field and, with a single contrast area of 1/4 %, is saturated when about 30% of the visual field is moving; (2) additional stationary contrasts inhibit visually induced self-motion, proportional to their density; and (3) the location in depth of the stationary contrasts has a significant effect upon this inhibition. Their effect is considerable when located in the background of the moving stimuli but weak when appearing in the foreground. It is concluded that dynamic visual spatial orientation relies mainly on information from the seen periphery, both retinal and depth.The perception of self-motion is based mainly on the integration of visual and vestibular motion information. It has been shown, for example. that visual information is essential for the perception of constant-velocity self-motion. since the vestibular system detects body acceleration only (Brandt, Dichgans, & Koenig, 1973;Dichgans & Brandt, 1974). The perception of self-motion, resulting, i.e., from rotation of the visual surround about the observer (circularvection or CV). was considered an illusion ("railroad illusion") in the older literature (Fischer & Kommuller, 1930; Helmholtz, 1896). and as a result its functional importance has been neglected. Clearly, when the body, for example, moves to the left at constant velocity, the visual field moves to the right, thus providing appropriate information concerning the direction and velocity of seIf-motion. That vision is essential for the sensation of constant-velocity body motion in vehicles can easily be detected if one closes the eyes, in which instance the sensation of motion ceases. Neurophysiological evidence for the underlying visual-vestibular integration has been provided by microelectrode studies of units in the vestibular nucleus in several species. Convergence of visual and vestibular motion information on these units has been found in the goldtish (Dichgans, Schmidt. & Graf, 1973), rabbit (Dichgans & Brandt. 1972; Leopold. Schmidt. Sterc, & Dichgans, 1973), and monkey (Henn, Young, & Support of this research was provided by the Deutsche Forschungsgemeinschaft (SFB 70. "Hirnforschung und Sinnesphysiologic"). Eugene R. Wist is on sabbatical leave from the Whitely Psychology Laboratories. Franklin and Marshall College. This study was conducted while Dr. Wist was a "U.S. Senior Scientist Awardee" of the German Alexander von Humboldt Fou ndation. Finley, 1973). For all three species, both constant-velocity visual stimuli and angular acceleration of the body were found to modulate unit activity.In contrast t...

The role of central and peripheral vision in perceiving the direction of self-motion

“…The order of surfaces in d~th may 1)e given by texture occlusion and disocclusion, motion perspective, stereopsis, and so on. Consistent with this notion is the evidence that both vection and postural adjustments are driven by motion of surfaces perceived to be in the background, but not by motion of surfaces perceived to be in the foreground (Brandt, Wist, & Dichgans, 1975;Ohmi, Howard, & Landolt, 1987).…”

The independence of dynamic spatial orientation from luminance and refractive error

“…In this study, the dependent variable consisted of the duration of these three stages, i.e., the time to onset of CV, the time from onset to saturation or full vection, and the duration of the aftereffect. These durations were measured since they most probably represent the best indica-'tors of the effectiveness of a given CV stimulus (Brandt, Wist, & Dichgans, 1975;Dichgans & Brandt, 1978). The procedure was repeated at least twice with right and left rotation of the drum for each luminance level.…”

Body Sway Induced by Depth Linear Vection in Reference to Central and Peripheral Visual Field.

“…Until recently, it has been thought that the peripheral visual field played a dominant role in self-motion perception, and the central visual field played little or no role [2,23]. Brandt et al [2] reported that circular vection could be induced when 30°displays were presented in the periphery but not when they were presented in the central visual field.…”

“…Brandt et al [2] reported that circular vection could be induced even when large parts of the central field were masked (up to 120°) [9]. On the other hand, Paulus et al [19] concluded that the foveal region has a powerful contribution.…”