3D after-effects are due to shape and not disparity adaptation

There are a variety of stereoscopic after-effccts in which exposure to a st imulus with a particular slant or curvature affects the perceived slant or curvature of a subsequently presented stimulus. These after-effects have be en explained as a consequence of fatigue (a decrease in responsiveness) amo ng neural mechanisms that are tuned to particular disparities or patterns o f disparity. In fact, a given disparity pattern is consistent with numerous slants or curvatures; to determine slant or curvature, the visual system m ust take the viewing distance into account. We took advantage of this prope rty to examine whether the mechanisms underlying the stereoscopic curvature after-effect are tuned to particular disparity patterns or to some other p roperty such as surface curvature. The results clearly support the second h ypothesis. Thus, 3D after-effects appear to be caused by adaptation among m echanisms specifying surface shape rather than among mechanisms signaling t he disparity pattern. (C) 2001 Elsevier Science Ltd. All rights reserved.