The stream/bounce display in which two identical visual objects move toward each other, coincide and then move apart can be perceived as either streaming through or bouncing off each other. Despite the ambiguity of the display, observers dominantly perceived the streaming. However, a sound burst/visual flash at the coincidence point biases observers’ percept toward the robust bouncing over a certain time (crossmodal/unimodal bouncing effect). Here, we used a block-based fMRI paradigm for investigating how the temporal establishment of the crossmodal bouncing would relate to brain responses. The presentation of the sound burst or visual flash was manipulated at the coincidence point. The presentation durations of the objects were varied before and after the coincidence point (pre/post-coincidence duration: 50, 100, 300 ms). Observers judged whether the objects appeared to stream through or bounce off each other. The behavioral data revealed that the crossmodal/unimodal bouncing reports significantly increased with the post-coincidence duration. The imaging data showed a tendency that the responses of the right anterior cingulate were enhanced with the longer post-coincidence duration, especially in the crossmodal condition. These findings suggest that the activity of the right anterior cingulate correlates with the degree of the temporal establishment of a crossmodal event perception.（本研究では、ストリームバウンス錯視を観察しているときの脳活動を、ブロックデザインの fMRIパラダイムを用いて検討した。その結果、特にクロスモーダルなバウンス知覚で、右帯状回の活動がバウンス後の刺激呈示時間が長くなると高まることが示された。）
Yousuke Kawachi, Michiaki Shibata, Hideaki Kawabata, Miho Kitamura, Jiro Gyoba.
