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Michael H. Herzog, Marc Boi, Haluk Ogmen; A Litmus Test for Retino- vs. Non-retinotopic Processing. Journal of Vision 2009;9(8):22. doi: https://doi.org/10.1167/9.8.22.
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© ARVO (1962-2015); The Authors (2016-present)
Most visual cortical areas are retinotopically organized and accordingly most visual processing is assumed to be processed within a retinotopic coordinate frame. However, in a series of psychophysical experiments, we have shown that features of elements are often non-retinotopically integrated when the corresponding elements are motion grouped. When this grouping is blocked, however, feature integration occurs within retinotopic coordinates (even though the basic stimulus paradigm is identical in both conditions and grouping is modulated by spatial or temporal contextual cues only). Hence, there is strong evidence for both retino- and non-retinotopic processing. However, it is not always easy to determine which of these two coordinate systems prevails in a given stimulus paradigm. Here, we present a simple psychophysical test to answer this question. We presented three squares in a first frame, followed by an ISI, the same squares shifted one position to the right, the same ISI, and the squares shifted back to their original position. When this cycle is repeated with ISIs longer than 100ms, three squares are perceived in apparent motion. With this specific set-up, features integrate between the central squares iff integration takes place non-retinotopically. With this litmus test we showed, for example, that motion processing is non-retinotopic whereas motion adaptation is retinotopic. In general, by adding the feature of interest to the central square, it can be easily tested whether a given stimulus paradigm is processed retino- or non-retinotopically.
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