Differential effects of central versus peripheral vision on egocentric and exocentric motion perception

Summary

Optokinetic stimuli allow for two perceptual interpretations. The observer may perceive himself as being stationary in a moving surround (egocentric motion perception) or he may experience an illusion of self-motion, so that the actually moving surroundings appear to be stable (exocentric motion perception).

Results

• 1. Circular motion of the entire surroundings (rotating drum) invariably leads to an apparent self-rotation (circularvection: CV), which is indistinguishable from an actual chair rotation.

• 2. Following stimulus onset, CV begins after a few seconds latency and slowly increases its apparent velocity until its saturation. CV may outlast the visual stimulus by as much as 30 sec. Latencies are independent of stimulus velocity.

• 3. Even with drum accelerations up to 15°/sec², stationary subjects cannot infer from the lack of vestibular input that only the drum is rotating.

• 4. With stimulation of the entire visual field or sufficiently large parts of the peripheral retina, the velocity of apparent self-rotation matches stimulus speed up to 90–120°/sec. At higher speeds, CV velocity lags behind stimulus speed and results in additional egocentric motion perception.

• 5. Masking the central visual field by black disks up to 120° in diameter scarcely diminishes CV. Conversely, if peripheral vision is precluded, stimulation of the central field up to 30° in diameter results in exclusive egocentric motion perception of the surround. With a central and peripheral stimulus equivalent in area, the peripheral stimulus predominates CV.

• 6. Simultaneous presentation of conflicting central and peripheral optokinetic stimuli (i.e., stimuli rotating in opposite directions) has shown that exocentric orientation depends on the peripheral stimulus whereas optokinetic nystagmus and egocentric motion perception rely on the center of the visual field.