title: Rescaling retinal size into perceived size: evidence for an occipital and parietal bottleneck.
abstract: The spatial and temporal context of an object influence its perceived size. Two visual illusions illustrate this nicely: the size adaptation effect and the Ebbinghaus illusion. Whereas size adaptation affects size rescaling of a target circle via a previously presented, differently sized adaptor circle, the Ebbinghaus illusion alters perceived size by virtue of surrounding circles. In the classical Ebbinghaus setting, the surrounding circles are shown simultaneously with the target. However, size underestimation persists when the surrounding circles precede the target. Such a temporal separation of inducer and target circles in both illusions permits the comparison of BOLD signals elicited by two displays that, although objectively identical, elicit different percepts. The current study combined both illusions in a factorial design to identify a presumed common central mechanism involved in rescaling retinal into perceived size. At the behavioral level, combining both illusions did not affect perceived size further. At the neural level, however, this combination induced functional activation beyond that induced by either illusion separately: An underadditive activation pattern was found within left lingual gyrus, right supramarginal gyrus, and right superior parietal cortex. These findings provide direct behavioral and functional evidence for the presence of a neural bottleneck in rescaling retinal into perceived size, a process vital for visual perception.
authors.affiliation: 1Research Center Jülich.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Kreutzer
authors.affiliation: 1Research Center Jülich.
authors.forename: Ralph
authors.initials: R
authors.lastname: Weidner
authors.affiliation: 1Research Center Jülich.|2Cologne University.
authors.forename: Gereon R
authors.initials: GR
authors.lastname: Fink
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009483:Neuropsychological Tests; D009903:Optical Illusions / Q000502:physiology*; D010775:Photic Stimulation; D012858:Size Perception / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult