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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)

運動方向選択性順応による運動視の脳内神経経路に関する fMRI 研究
Neural basis of visual motion perception in humans with velocity selectivity studied by fMRI with direction selective adaptation

  • O1-G-3-1
  • 栗木 一郎 / Ichiro Kuriki:1,2 山田 祥之 / Yoshiyuki Yamada:2 松宮 一道 / Kazumichi Matsumiya:1,2 塩入 諭 / Satoshi Shioiri:1,2 
  • 1:東北大学 / Research Institute of Electrical Communication, Tohoku University, Japan 2:東北大学大学院情報科学研究科 / Graduate School of Information Sciences, Tohoku University, Japan 

Human visual system is known to have at least two kinds of visual motion mechanisms that differ in their most sensitive velocity (Shioiri and Matsumiya, 2009). However, the mechanisms especially for very slow motion, and its interaction with the fast motion signal are unknown. We addressed these issues with direction selective adaptation technique in both psychophysical and fMRI methods. The subject adapted to a radial gray grating (subtended 2-7 ° in eccentricity; 6 cycles per round), which moved in either clockwise or counter-clockwise direction at either high (4/3 rotation/s) or low (1/18 rotation/s) angular velocity around the fixation point. The adapting stimulus was presented continuously for 12 (± 3) s on average, and test stimulus was presented for 3 s; changes between stimuli were made gradually in a ramped contrast envelope (0.5 s). This cycle was repeated until 10 trials were collected per condition, and the adapting condition (direction and speed) was identical during a run. The subjects were asked to report the direction of test stimulus with buttons, as soon as possible. All experiments were conducted in the fMRI scanner to record BOLD signal and the subjects' responses. Both crossed and uncrossed adaptations between two velocities were confirmed in behavioral result, measured by reaction times. The BOLD responses to the test stimuli were analyzed in visual area ROIs, localized by retinotopic mapping. Direction-selective aftereffect was found with statistical significance in MT+ only for the fast test stimulus after adaptation to the fast motion. In V4, the significant aftereffect was observed for both test stimuli only after adaptation to slow motion; V1, V2, and V3 showed the same trend with statistical significance. V3AB showed no significant aftereffect for all conditions, but the trend was an intermediate of the two types. The significant aftereffect for slow adaptation in V1-V3 and V4 implies that slow motions may be processed in the ventral stream as a pattern motion. We found significant interaction of fast and slow motion signals also in the ventral stream, including the early stage of visual cortex.

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