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視覚 3
Visual System 3

開催日 2014/9/11
時間 18:00 - 19:00
会場 Room G(303)
Chairperson(s) 藤田 一郎 / Ichiro Fujita (大阪大学大学院生命機能研究科 / Osaka University, Graduate School of Frontier Biosciences, Japan)
稲場 直子 / Naoko Inaba (京都大学 学際融合教育研究推進センター / Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Japan)

Representation of viewpoints at different spatial scales in human occipital face area

  • O1-G-3-4
  • Chienhui Kao:1 Topi Tanskanen:1 Kenichi Ueno:2 R. Allen Waggoner:1 Keiji Tanaka:1 Kang Cheng:1,2 
  • 1:Cognitive Brain Mapping, RIKEN Brain Science Institute, Wako, Japan 2:Support Unit for Functional Magnetic Resonance Imaging, RIKEN Brain Science Institute, Wako, Japan 

Face recognition is a critical social skill for primates. One of the key abilities in face recognition is the identification and generalization of a face across a variety of viewpoints. Over the past two decades, several studies have demonstrated the existence of neurons selective for face viewpoints in macaque inferotemporal (IT) cortex (Freiwald & Tsao, 2010; Wang et al., 1996, 1998). However, the exact mechanism as to how different face viewpoints are processed in human visual system is still under debate. In this study, we asked whether human occipito-temporal cortex (homologous to macaque IT) is sensitive to different viewpoints of a face and if so, how the viewpoints are represented in this area.
We used a 4T MRI system and adapted a continuous and periodic stimulation paradigm to investigate the viewpoint-selective representation in occipital face area (OFA) that was individually localized by faces compared to other objects in a separate session. Each observer, while maintaining fixation at a central point and performing a color detection task, viewed for 36s face images of the same identity seen from viewpoint changing continuously, which was followed by a 24s blank period. The face rotated from the left profile to the frontal view and then to the right profile, or from a reverse direction. Each image was presented for 0.8s and the viewpoint differed by 5 degree between successive images. Each fMRI run contained 16 cycles of continuous viewpoint-changing periods, during which 8 face identities were repeated twice in a counter-balance order. In total, four runs were collected. Functional images were acquired at two in-plane resolutions in separate sessions: 1.9 x 1.9 and 0.75 x 0.75 mm2.
We found that BOLD responses were temporally modulated by the changing viewpoint in OFA. At the coarser resolution, many voxels were found to prefer multiple viewpoints, whereas most of voxels preferred single viewpoints at the finer resolution. These results, obtained across different spatial resolutions, suggest that the viewpoints may be represented in a columnar fashion in OFA.

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