Visual clues to orientation Three types of visual information contribute to our sense of gravitational orientation Motion of the visual surroundings Roll rotation of a large field textured display induces an illusion of self-rotation(vection)and self-tilt Tilt of the visual frame Tilt can cause displacement of the visual or postural vertical Visual polarity Intrinsic polarity -Objects have a principle axis and perceptual top"and"bottom Extrinsic polarity -Spatial relationships between objects define principle axis and" top"or"bottom 16. 423 SBE(Neurovestibular Countermeasures)16.423 SBE (Neurovestibular Countermeasures) Visual Clues to Orientation • Three types of visual information contribute to our sense of gravitational orientation: – Motion of the visual surroundings • Roll rotation of a large field textured display induces an illusion of self-rotation (vection) and self-tilt. – Tilt of the visual frame • Tilt can cause displacement of the visual or postural vertical. – Visual polarity • Intrinsic polarity - Objects have a principle axis and perceptual “top” and “bottom”. • Extrinsic polarity - Spatial relationships between objects define principle axis and “top” or “bottom