Abstract
A wealth of studies has found that adapting to second-order visual stimuli has little effect on the perception of first-order stimuli. This is physiologically and psychologically troubling, since many cells show similar tuning to both classes of stimuli, and since adapting to first-order stimuli leads to aftereffects that do generalize to second-order stimuli. Focusing on high-level visual stimuli, we recently proposed the novel explanation that the lack of transfer arises partially from the characteristically different backgrounds of the two stimulus classes. Here, we consider the effect of stimulus backgrounds in the far more prevalent, lower-level, case of the orientation tilt aftereffect. Using a variety of first- and second-order oriented stimuli, we show that we could increase or decrease both within- and cross-class adaptation aftereffects by increasing or decreasing the similarity of the otherwise apparently uninteresting or irrelevant backgrounds of adapting and test patterns. Our results suggest that similarity between background statistics of the adapting and test stimuli contributes to low-level visual adaptation, and that these backgrounds are thus not discarded by visual processing but provide contextual modulation of adaptation. Null cross-adaptation aftereffects must also be interpreted cautiously. These findings reduce the apparent inconsistency between psychophysical and neurophysiological data about first- and second-order stimuli.
Highlights
The ubiquity of adaptation makes it a major experimental paradigm both in its own right and as a methodological tool for investigating other questions
Using high level visual stimuli, we recently found a new form of contingent adaptation which we call the background similarity effect (Wu et al, 2009)
We first show that adaptation to a second-order orientation transferred more to first-order bars when the adapting and test stimuli had better matched backgrounds
Summary
The ubiquity of adaptation makes it a major experimental paradigm both in its own right and as a methodological tool for investigating other questions. Adaptation is measured by means of aftereffects, and a central issue is how the strength of such aftereffects depends on the relationship between adapting and test stimuli. It is well known that to produce strong aftereffects, adapting and test stimuli should have similar features. To maximize the tilt aftereffect, the adapting and test orientations should have matched retinal location (Gibson & Radner, 1937) and spatial frequency (Ware & Mitchell, 1974). We will refer to this as the foreground similarity effect because the matched feature (e.g., spatial frequency) is a property of the foreground feature (e.g., orientation) whose adaptation is measured. The effect is easy to understand because many visual cells are jointly tuned to multiple features (e.g., orientation and spatial frequency), and by matching them, the adapting and test stimuli will engage maximally
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