title: The Poggendorff illusion driven by real and illusory contour: Behavioral and neural mechanisms.
abstract: The Poggendorff illusion refers to the phenomenon that the human brain misperceives a diagonal line as being apparently misaligned once the diagonal line is interrupted by two parallel edges, and the size of illusion is negatively correlated with the angle of interception of the oblique, i.e. the sharper the oblique angle, the larger the illusion. This optical illusion can be produced by both real and illusory contour. In this fMRI study, by parametrically varying the oblique angle, we investigated the shared and specific neural mechanisms underlying the Poggendorff illusion induced by real and illusory contour. At the behavioral level, not only the real but also the illusory contours were capable of inducing significant Poggendorff illusion. The size of illusion induced by the real contour, however, was larger than that induced by the illusory contour. At the neural level, real and illusory contours commonly activated more dorsal visual areas, and the real contours specifically activated more ventral visual areas. More importantly, examinations on the parametric modulation effects of the size of illusion revealed the specific neural mechanisms underlying the Poggendorff illusion induced by the real and the illusory contours, respectively. Left precentral gyrus and right middle occipital cortex were specifically involved in the Poggendorff illusion induced by the real contour. On the other hand, bilateral intraparietal sulcus (IPS) and right lateral occipital complex (LOC) were specifically involved in the Poggendorff illusion induced by the illusory contour. Functional implications of the above findings were further discussed.
authors.affiliation: Center for Studies of Psychological Application and School of Psychology, South China Normal University, Guangzhou 510631, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Shen
authors.affiliation: School of Education, Soochow University, Suzhou 215123, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Center for Studies of Psychological Application and School of Psychology, South China Normal University, Guangzhou 510631, China; Epilepsy Center, Guangdong 999 Brain Hospital, Guangzhou 510631, China; Guangdong Key Laboratory of Mental Health and Cognitive Science, South China Normal University, Guangzhou 510631, China. Electronic address: qi.chen27@gmail.com.
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
mesh_terms: D000704:Analysis of Variance; D001931:Brain Mapping; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D007088:Illusions / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000000981:diagnostic imaging / Q000502:physiology*; D009778:Occipital Lobe / Q000000981:diagnostic imaging / Q000502:physiology*; D009903:Optical Illusions / Q000502:physiology*; D009949:Orientation; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D011601:Psychophysics; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: Illusory contour; Parametric modulation effect; Poggendorff illusion; Real contour; fMRI