Object-motion detection affected by concurrent self-motion perception: Psychophysics of a new phenomenon

Abstract

Thresholds for object-motion detection are significantly raised when concurrent self-motion perception is induced by either vestibular, or visual, or cervico-somatosensory stimulation. (1) Active sinusoidal horizontal head oscillations with compensatory vestibulo-ocular reflex (VOR) and foveal or eccentrical target presentation; (2) ‘passive’ head movements with fixation suppression of the VOR; (3) pure body oscillations with the head fixed in space (cervical stimulation); (4) optokinetically induced apparent self-motion (circularvection). This new visual phenomenon of a physiological ‘inhibitory interaction’ between object- and self-motion perception seems to have a somatosensory motor analogue. It may reflect the disadvantageous side effect due to unspecificness of an otherwise beneficial space constancy mechanism, which provides us with the image of a stable world during locomotion.