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Rudiger Heydt; Figure-ground organization in the visual cortex. Journal of Vision 2003;3(12):16. doi: 10.1167/3.12.16.
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© ARVO (1962-2015); The Authors (2016-present)
Many phenomena of visual perception can be understood as the result of processing strategies centered around the problem of a 3D interpretation of 2D images. I will discuss recent results showing that figure-ground organization takes place at low levels in the visual cortex. The basic finding is that many neurons in V2 respond with different strengths to the same contrast border, depending on the side of the figure to which the border belongs, implying processing of the whole figure. Side-of-figure information is often combined with selectivity for stereoscopic edges and/or selectivity for borders defined by motion. In this case, the preferred figure side is generally the same as the ‘near’ side of the preferred 3D edge (as given by stereo or motion cues). This means that the cortex ‘interprets’ contrast borders as occluding contours as if the figure were an object in 3D space. Further experiments showed that the neural figure-ground signal for a given contrast edge covaries with perceptual border assignment in displays in which the context suggests occlusion or transparent overlay. Various observations point to low-level mechanisms: side-of-figure signals emerge with short latency and without involvement of attention; neurons are often selective for some border ownership cues, but not others, as if different specific mechanisms are being combined in stages. These results suggest that figure-ground organization is one of the main functions of area V2.
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