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Marius Peelen, Daniel Kaiser; Positional regularity disrupts independent coding of multiple objects in visual cortex. Journal of Vision 2017;17(10):572. doi: 10.1167/17.10.572.
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© ARVO (1962-2015); The Authors (2016-present)
The human visual system has adapted to efficiently process cluttered scenes containing dozens of objects. The regular arrangement of these objects critically contributes to the efficiency of naturalistic vision. Recent studies investigating multiple object perception have demonstrated that visual cortex responses to multi-object displays can be accurately modeled by a linear combination of responses to individual objects, revealing independent processing of simultaneously presented objects. Here we use fMRI to show that this independence breaks down when objects are positioned according to frequently experienced configurations. Participants viewed pairs of objects that formed minimalistic two-object scenes (e.g., a "living room" consisting of a sofa and television) presented in their regularly experienced spatial arrangement or in an irregular arrangement (with the object positions interchanged). Additionally, every single object was presented centrally and in isolation. Multi-voxel activity patterns evoked by the object pairs were modeled as the average of the response patterns evoked by the two single objects forming the pair. Strikingly, in object-selective cortex (OSC), but not in early visual cortex, this approximation was significantly less accurate for the regularly than the irregularly positioned pairs. This result was replicated in a second experiment that additionally ruled out that these effects were mediated by scene imagery. These findings indicate that during naturalistic vision – when objects appear in regular arrangements – OSC does not represent the scene's objects independently. Rather, regularly co-occurring objects may be partially integrated in OSC. This may serve to reduce the descriptive complexity of the scene.
Meeting abstract presented at VSS 2017
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