title: Topographic representation of an occluded object and the effects of spatiotemporal context in human early visual areas.
abstract: Occlusion is a primary challenge facing the visual system in perceiving object shapes in intricate natural scenes. Although behavior, neurophysiological, and modeling studies have shown that occluded portions of objects may be completed at the early stage of visual processing, we have little knowledge on how and where in the human brain the completion is realized. Here, we provide functional magnetic resonance imaging (fMRI) evidence that the occluded portion of an object is indeed represented topographically in human V1 and V2. Specifically, we find the topographic cortical responses corresponding to the invisible object rotation in V1 and V2. Furthermore, by investigating neural responses for the occluded target rotation within precisely defined cortical subregions, we could dissociate the topographic neural representation of the occluded portion from other types of neural processing such as object edge processing. We further demonstrate that the early topographic representation in V1 can be modulated by prior knowledge of a whole appearance of an object obtained before partial occlusion. These findings suggest that primary "visual" area V1 has the ability to process not only visible or virtually (illusorily) perceived objects but also "invisible" portions of objects without concurrent visual sensation such as luminance enhancement to these portions. The results also suggest that low-level image features and higher preceding cognitive context are integrated into a unified topographic representation of occluded portion in early areas.
authors.affiliation: Center for Information and Neural Networks, National Institute of Information and Communications Technology, Osaka, 565-0871, Japan, The Japan Society for the Promotion of Science, Tokyo 102-8472, Japan, Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-Cho, Sakyo-ku, Kyoto City, Kyoto 606-8501, Japan, National Center of Neurology and Psychiatry, Tokyo 187-8502, Japan, Human Brain Research Center, Graduate School of Medicine, Kyoto University, Yoshida-Konoe-Cho, Sakyo-Ku, Kyoto City, Kyoto 606-8507, Japan, and Kyoto Institute of Technology, Matsugasaki Hashikami-Cho, Sakyo-Ku, Kyoto City, Kyoto 606-8585, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ban
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Hanakawa
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Urayama
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Aso
authors.forename: Hidenao
authors.initials: H
authors.lastname: Fukuyama
authors.forename: Yoshimichi
authors.initials: Y
authors.lastname: Ejima
mesh_terms: D000328:Adult; D001931:Brain Mapping; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology*; D014796:Visual Perception