title: Involvement of the Extrageniculate System in the Perception of Optical Illusions: A Functional Magnetic Resonance Imaging Study.
abstract: Research on the neural processing of optical illusions can provide clues for understanding the neural mechanisms underlying visual perception. Previous studies have shown that some visual areas contribute to the perception of optical illusions such as the Kanizsa triangle and Müller-Lyer figure; however, the neural mechanisms underlying the processing of these and other optical illusions have not been clearly identified. Using functional magnetic resonance imaging (fMRI), we determined which brain regions are active during the perception of optical illusions. For our study, we enrolled 18 participants. The illusory optical stimuli consisted of many kana letters, which are Japanese phonograms. During the shape task, participants stated aloud whether they perceived the shapes of two optical illusions as being the same or not. During the word task, participants read aloud the kana letters in the stimuli. A direct comparison between the shape and word tasks showed activation of the right inferior frontal gyrus, left medial frontal gyrus, and right pulvinar. It is well known that there are two visual pathways, the geniculate and extrageniculate systems, which belong to the higher-level and primary visual systems, respectively. The pulvinar belongs to the latter system, and the findings of the present study suggest that the extrageniculate system is involved in the cognitive processing of optical illusions.
authors.affiliation: Department of Dementia Prevention and Therapeutics, Graduate School of Medicine, Mie University, Mie, Japan; Department of Neurology, Graduate School of Medicine, Mie University, Mie, Japan.
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Tabei
authors.affiliation: Department of Dementia Prevention and Therapeutics, Graduate School of Medicine, Mie University, Mie, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Satoh
authors.affiliation: Department of Dementia Prevention and Therapeutics, Graduate School of Medicine, Mie University, Mie, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Kida
authors.affiliation: Faculty of Medicine, Mie University, Mie, Japan.
authors.forename: Moeni
authors.initials: M
authors.lastname: Kizaki
authors.affiliation: Faculty of Medicine, Mie University, Mie, Japan.
authors.forename: Haruno
authors.initials: H
authors.lastname: Sakuma
authors.affiliation: Department of Radiology, Graduate School of Medicine, Mie University, Mie, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Sakuma
authors.affiliation: Department of Dementia Prevention and Therapeutics, Graduate School of Medicine, Mie University, Mie, Japan; Department of Neurology, Graduate School of Medicine, Mie University, Mie, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Tomimoto
mesh_terms: D001931:Brain Mapping; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009903:Optical Illusions / Q000502:physiology*; D017397:Prefrontal Cortex / Q000502:physiology*; D020649:Pulvinar / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult