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Tanya Wen, Chun-Chia Kung; Using Functional Magnetic Resonance Imaging to Explore the Flashed Face Distortion Effect. Journal of Vision 2014;14(10):121. doi: 10.1167/14.10.121.
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© ARVO (1962-2015); The Authors (2016-present)
The Flashed Face Distortion (FFD) is a recently discovered illusion, that after a while of viewing, the faces become distorted and alien-like. The FFD is displayed by presenting a sequence of eye-aligned faces at a steady pace in the peripheral vision of the observer. This study uses fMRI to explore the changes in the human brain when perceiving different strengths of this illusion. Behaviorally, FFD strength was found to be influenced by the number of faces per sequence when the number was small. In this experiment, four levels of manipulations were conducted: 1) one fixed face changing only illumination, 2) two alternating faces, 3) a sequence of three faces cycling repeatedly, and 4) a sequence of non-repeated faces. The four conditions were presented in pseudo-randomized blocks, followed by a rating phase where participants subjectively rated the magnitude of the perceived distortion on a four-point scale. In addition to the main experiment, localizers were performed to identify face-selective areas including the FFA, OFA, and STS in the right hemisphere, and retinotopic mapping allowed demarcation of visual areas V1~V4, which were later overlapped with FFD task-driven activation. Within these ROIs, the BOLD signals were compared across the four FFD conditions and correlated with subjects FFD ratings. Multiple regression analysis, including the rating of FFD strength and a dummy variable for subject, revealed significant regression of perceived FFD strength on the PSC in these ROIs. This regression also entered whole-brain voxelwise analysis, which additionally revealed non-visual areas, including the precuneus, posterior cingulate, bilateral insular cortices, and inferior parietal lobules (IPL) negatively correlate with perceptual FFD strength. Taken together, these results suggest that the brain network consisting of the early visual cortex, higher level face-selective areas, as well as fronto-parietal areas are involved in modulating the FFD illusion.
Meeting abstract presented at VSS 2014
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