title: Visual crowding in V1.
abstract: In peripheral vision, objects in clutter are difficult to identify. The exact cause of this "crowding" effect is unclear. To perceive coherent shapes in clutter, the visual system must integrate certain local features across receptive fields while preventing others from being combined. It is believed that this selective feature integration-segmentation process is impaired in peripheral vision, leading to crowding. We used functional magnetic resonance imaging (fMRI) to investigate the neural origin of crowding. We found that crowding was associated with suppressed fMRI signal as early as V1, regardless of whether attention was directed toward or away from a target stimulus. This suppression in early visual cortex was greatest for stimuli that produced the strongest crowding. In contrast, the pattern of activity was mixed in higher level visual areas, such as the lateral occipital cortex. These results support the view that the deficiency in feature integration and segmentation in peripheral vision is present at the earliest stages of cortical processing.
authors.affiliation: Neuroscience Graduate Program.
authors.forename: Rachel
authors.initials: R
authors.lastname: Millin
authors.affiliation: Neuroscience Graduate Program, Current address: Deallus Group, Los Angeles, CA 90025, USA.
authors.forename: A Cyrus
authors.initials: AC
authors.lastname: Arman
authors.affiliation: School of Optometry, University of California, Berkeley, CA 94720-2020, USA and.
authors.forename: Susana T L
authors.initials: ST
authors.lastname: Chung
authors.affiliation: Neuroscience Graduate Program, Department of Psychology, University of Southern California, Los Angeles, CA 90089-1061, USA.
authors.forename: Bosco S
authors.initials: BS
authors.lastname: Tjan
mesh_terms: D000704:Analysis of Variance; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D011601:Psychophysics; D013334:Students; D013997:Time Factors; D014495:Universities; D014793:Visual Cortex / Q000098:blood supply / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*; D014795:Visual Pathways / Q000098:blood supply / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
chemical_list: D010100:Oxygen
keywords: fMRI; peripheral vision; primary visual cortex; visual crowding