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      Attention-dependent representation of a size illusion in human V1

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      Author
      Fang, F.
      Boyacı, Hüseyin
      Kersten, D.
      Murray, S.O.
      Date
      2008
      Source Title
      Current Biology
      Print ISSN
      0960-9822
      Electronic ISSN
      1879-0445
      Publisher
      Cell Press
      Volume
      18
      Issue
      21
      Pages
      1707 - 1712
      Language
      English
      Type
      Article
      Item Usage Stats
      139
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      126
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      Abstract
      One of the most fundamental properties of human primary visual cortex (V1) is its retinotopic organization, which makes it an ideal candidate for encoding spatial properties, such as size, of objects. However, three-dimensional (3D) contextual information can lead to size illusions that are reflected in the spatial pattern of activity in V1 [1]. A critical question is how complex 3D contextual information can influence spatial activity patterns in V1. Here, we assessed whether changes in the spatial distribution of activity in V1 depend on the focus of attention, which would be suggestive of feedback of 3D contextual information from higher visual areas. We presented two 3D rings at close and far apparent depths in a 3D scene. When subjects fixated its center, the far ring appeared to be larger and occupy a more eccentric portion of the visual field, relative to the close ring. Using functional magnetic resonance imaging, we found that the spatial distribution of V1 activity induced by the far ring was also shifted toward a more eccentric representation of the visual field, whereas that induced by the close ring was shifted toward the foveal representation, consistent with their perceptual appearances. This effect was significantly reduced when the focus of spatial attention was narrowed with a demanding central fixation task. We reason that focusing attention on the fixation task resulted in reduced activity in-and therefore reduced feedback from-higher visual areas that process the 3D depth cues.
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      http://hdl.handle.net/11693/22967
      Published Version (Please cite this version)
      http://dx.doi.org/10.1016/j.cub.2008.09.025
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      • Aysel Sabuncu Brain Research Center (BAM) 197
      • Department of Psychology 170
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