Transparent Motion Perception as Detection of Unbalanced Motion
Signals I: Psychophysics
Ning Qian, Richard A. Andersen and Edward H. Adelson, J. Neurosci.
1994, 14:7357-7366.
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Abstract
Our visual system can solve the difficult problem of representing
multiple motions in the same part of the visual space, the motion
transparency problem. We investigated the conditions under which
transparent motion perception occurs through psychophysical
observations, using a series of visual displays composed of two simple
patterns moving in opposite directions. We found that whenever a
display has finely balanced opposing motion signals in all local
regions, it is perceptually non-transparent. The displays that
appeared transparent always contain locally unbalanced motion signals,
with some local regions having net motion signals in one direction and
some other regions in the opposite direction. These interdigitating
net motion signals in both directions appear to be integrated
separately to form two overlapping transparent surfaces. Displays
which were spatially balanced could be made perceptually transparent
if the two components moving in opposite directions were at different
stereo depth planes or had different spatial frequency contents. Our
results can be explained by proposing a disparity and spatial
frequency specific suppression stage in the motion pathway, at which
motion signals of different directions, but of the same disparity and
spatial frequency contents, locally inhibit each other. Such a
mechanism would suppress noise input to the motion system, which
generally activates several direction channels simultaneously, and
would still not eliminate activity evoked by transparent surfaces
which are at different depths or have different textures.
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