Asymmetric global motion integration in drifting Gabor arrays.

Abstract

We examined how ambiguous motion signals are integrated over space to support the unambiguous perception of global motion. The motion of a Gaussian windowed drifting sine grating (Gabor) is consistent with an infinite number of grating velocities. To extract the consistent global motion of multi-Gabor arrays, the visual system must integrate ambiguous motion signals from disparate regions of visual space. We found an interaction between spatial arrangement and global motion integration in this process. Linear arrays of variably oriented Gabor elements appeared to move more slowly, reflecting suboptimal integration, when the direction of global translation was orthogonal to the line as opposed to along it. Circular arrays of Gabor elements appeared to move more slowly when the global motion was an expansion or contraction rather than a rotation. However, there was no difference in perceived speed for densely packed annular arrays for these global motion pattern directions. We conclude that the region over which ambiguous motion is integrated is biased in the direction of global motion, and the concept of the association field, held to link like elements along a contour, needs to be extended to include global motion computation over disparate elements referencing the same global motion.