Abstract
Background
Although it is known that high-level spatial attention affects adaptation for a variety of stimulus features (including binocular disparity), the influence of attentional control —and the associated awareness— on adaptation has remained unexplored. We developed a surface slant adaptation stimulus with conflicting monocular and binocular slant signals that instigated two mutually exclusive surface percepts with opposite slants, enabling us to dissociate slant adaptation due to awareness from stimulus-induced slant (Brouwer, van Ee & Schwarzbach, J. NeuroSci, 2005, 25, 10403–13; for demonstrations of the stimulus: http://www.phys.uu.nl/~vanee/).
Results
We found that slant aftereffects (SAE) for monocular and binocular test patterns had an opposite sign when measured simultaneously. In addition, the magnitude of SAE did not correlate with the magnitude of perceived slant. For example: although a disparity gradient induces a larger perceived slant in the presence of a reference, its SAE is smaller. Using adaptation to one slant cue, and testing with the other cue, we demonstrated that multiple slant signals adapt independently.
Conclusion
We conclude that slant adaptation occurs before the level of slant awareness. Our findings place the site of stereoscopic slant adaptation after disparity and eye posture are interpreted for slant [as demonstrated by Berends, Liu & Schor (JOV, 2005, 5, 71–80), using that disparity scales with distance], but before other slant signals are integrated for the resulting awareness of the presented slant stimulus.