Retinotopy of visual masking and non-retinotopic perception during masking
Due to the movements of the observer and those of objects in the environment, retinotopic representations are highly unstable during ecological viewing conditions. The phenomenal stability of our perception suggests that retinotopic representations are transformed into non-retinotopic representations. It remains to show, however, which visual processes operate under retinotopic representations and which ones operate under non-retinotopic representations. Visual masking refers to the reduced visibility of one stimulus, called the target, due to the presence of a second stimulus, called the mask. Masking has been used extensively to study the dynamic aspects of visual perception. Previous studies using Saccadic Stimulus Presentation Paradigm (SSPP) suggested both retinotopic and non-retinotopic bases for visual masking. In order to understand how the visual system deals with retinotopic changes induced by moving targets, we investigated the retinotopy of visual masking and the fate of masked targets under conditions that do not involve eye movements. We have developed a series of experiments based on a radial Ternus-Pikler display. In this paradigm, the perceived Ternus-Pikler motion is used as a non-retinotopic reference frame to pit retinotopic against non-retinotopic visual masking hypothesis. Our results indicate that both metacontrast and structure masking are retinotopic. We also show that, under conditions that allow observers to read-out effectively non-retinotopic feature attribution, the target becomes visible at a destination different from its retinotopic/spatiotopic location. We discuss the implications of our findings within the context of ecological vision and dynamic form perception.