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Hiroaki Shigemasu, Pengfei Yan; Stereo-curvature Aftereffect at Multiple Processing Levels: an fMRI study. Journal of Vision 2016;16(12):839. doi: https://doi.org/10.1167/16.12.839.
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© ARVO (1962-2015); The Authors (2016-present)
It has not been clear what levels of cortical process are involved in stereo-curvature aftereffect ranging from retinal disparity to perceived shape process. In this study, we conducted an fMRI experiment to probe multi-level adaptation of stereo-curvature aftereffects across ROIs defined by retinotopic mapping and functional localizer. We used random dot stereograms which depicted horizontal hemicylinder for adaptation and test stimuli. In order to separately investigate the adaptation to distinct sources, we used two types of fixation point which (1) moved along Lissajous path in depth and (2) were static to manipulate adaptation to local retinal disparity, and used three types of adaptation stimuli which involved dynamic changes (1) in size, (2) in length of depth axis, and (3) no change to manipulate the levels of shape processing. Participants just fixated or tracked the fixation point in adaptation phase and observed test stimuli with static fixation in test phase. For the index of adaptation, we compared BOLD signal change from baseline during adaptation phase (6.6 s) and test phase (1 s). The results showed that adaptation effect without constant local disparity information was significantly smaller in V1, V2 and also middle dorsal area (KO/V3B). The adaptation to the shape related information was found in both dorsal and ventral areas but showed different properties among them. The size variant adaptation effect (i.e. the adaptation effect depended on the change of shape curvature) was found in POIPS region but the size invariance was found in VP and ventro-lateral areas (hV4, LO). Also, adaptation to the averaged disparity information seems to be processed in high dorsal area (V7) and IPS areas (VIPS/V7*, POIPS and DIPS), suggesting that these areas may involve a low-order calculation of disparity which may be used to encode depth metrically while ventral pathway encode categorical shape.
Meeting abstract presented at VSS 2016
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