Perceived orientation, motion, and configuration of the body during viewing of an off-vertical, rotating surface

Abstract

Dynamic patterns of activity from multiple receptor systems, as well as efferent signals associated with voluntary movements, influence perceived body motion. The experiment to be described explored how these factors interrelate in influencing apparent body motion. It involved exposing stationary, reclining subjects to a patterned surface which rotated around a vertical or an off-vertical axis. We were able to create situations in which the combined patterns of visual, otolithic, somatosensory, and semicircular canal stimulation actually present were not consistent with body motion in a terrestrial environment. Nevertheless, all of our subjects experienced self-rotation and displacement around a vertical axis. A variety of changes in apparent body orientation, body configuration, and slant ofthe visual surface occurred concurrently with the elicitation of apparent body rotation. These perceptual remappings were such as to be consistent both with the rotary visual stimulation present and with the absence of changes in otolithic and somatosensory inputs. They were achieved through a reinterpretation of the static otolithic, somatosensory, and proprioceptive signals present. Our findings demonstrate that perceived body motion also depends on representations of what combinations of sensory input are possible in a terrestrial environment.

Perceptual Centering Effects in Body Orientation

“…: +503-4135426 Fax: +503-4135348 tibular convergence in the vestibular nuclei (Goldberg and Fernandez 1984;DiZio and Lackner 1986). However, it has not been explained why the viewer would, as a consequence, misperceive his or her own orientation to gravity or relative orientations of his or her body segments, as observed in experiments of DiZio and Lackner (1986) (Fig.…”

“…When the head, torso, and disk were all horizontal (Condition A, not shown), subjects experienced self-rotation around a vertical axis through the head, but correctly perceived the orientations of the head, torso, and disk to gravity. In addition, DiZio and Lackner (1986) show that if perceived self-rotation is induced by visual rotation about a nonvertical axis, or if the subject's head is tilted forward or back during disk viewing, then orientations of the disk, head, and torso are perceptually remapped to construct one of a discrete set of perceptual illusions (Fig. 1).…”

“…1). These perceptual illusions are DiZio and Lackner (1986). At the top are shown the actual orientations in which subjects were tested.…”

“…A robust characteristic of the DiZio and Lackner (1986) data is the association to a particular stimulus condition of a discrete, classifiable set of several orientation perceptions among the subject population (Fig. 1).…”

Direct perception of global invariants is not a fruitful notion

“…This explains the fact that the illusion of bodily rotation relative to the earth is robust only when acceleration is prevented, for example, when the head is subjected to passive restraint (e.g., Brandt et al 1973;Ohmi et al 1987;Wertheim 1987). The illusion is eliminated by head movements, and is often suppressed even by eye movements (e.g., DiZio & Lackner 1986). Similarly, it is largely because subjects in moving rooms are not restrained that we suggested that their perceptions may be veridical (sect.…”