Citation

Sauvan XM. Vis. Veh. 1998; 6: 297-304.

Copyright

(Copyright © 1998, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Curvilinear and rectilinear vections were studied by using two drifting vertical sine wave gratings displayed at an eccentricity of 60 deg on either side of the subjects' sagittal plane. Curvilinear vection corresponds to the sensation of taking a bend and rectilinear vection of moving in a straight line. Curvilinear vection is similar to the actual observer's movement in a curved path. It is induced by asymmetrical visual stimuli with respect to contrast, spatial frequency or angular velocity. The thresholds of perception of these vections were measured by the method of limits. These thresholds define a spatiotemporal zone of perception of rectilinear vection centered upon the low spatial frequencies and the middle temporal frequencies. Moreover, a Weber's law was found such that a mean relative differential threshold of the angular velocities of the two gratings of about 41% is necessary for inducing curvilinear vection. Also, the perceived velocity and degree of curvature of curvilinear vection varied differently as a function of contrast, spatial frequency, temporal frequency and angular velocity. All results highlight the role of the spatiotemporal structure of the optical flow in perceiving self-motion. Furthermore, it is suggested that two different visual systems control ambient vision: a lower level system requiring peripheral vision and a higher level system working in the central visual field and using complex visual information such as depth cues.