Spatial localization investigated by continuous pointing during visual and gravitoinertial changes

Abstract

In order to accurately localize an object, human observers must integrate multiple sensory cues related to the environment and/or to the body. Such multisensory integration must be repeated over time, so that spatial localization is constantly updated according to environmental changes. In the present experimental study, we examined the multisensory integration processes underlying spatial updating by investigating how gradual modifications of gravitoinertial cues (i.e., somatosensory and vestibular cues) and visual cues affect target localization skills. These were assessed by using a continuous pointing task toward a body-fixed visual target. The "single" rotation of the gravitoinertial vector (produced by off-axis centrifugation) resulted in downward pointing errors, which likely were related to a combination of oculogravic and somatogravic illusions. The "single" downward pitch rotation of the visual background produced an elevation of the arm relative to the visual target, suggesting that the rotation of the visual background caused an illusory target elevation (induced-motion phenomenon). Strikingly, the errors observed during the "combined" rotation of the visual background and of the gravitoinertial vector appeared as a linear combination of the errors independently observed during "single" rotations. In other words, the centrifugation effect on target localization was reduced by the visual background rotation. The observed linear combination indicates that the weights of visual and gravitoinertial cues were similar and remained constant throughout the stimulation.

To Pass or not to Pass: More a Question of Body Orientation than Visual Cues

“…For example, it could be particularly interesting to question the contribution of specific sensory cues in the reweighting processes affecting the combination between available spatial references. In this vein, the changes observed in the weight of a specific spatial reference over time could be highly informative to better understand how these spatial cues dynamically interact (Bringoux et al, 2009;Scotto Di Cesare, Bringoux, Bourdin, Sarlegna, & Mestre, 2011).…”