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Cheng Qiu, Daniel Kersten, Cheryl A. Olman; The effect of attention and dot coherence on fMRI responses to 3D structure-from-motion. Journal of Vision 2014;14(10):296. doi: 10.1167/14.10.296.
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Humans can easily perceive the three-dimensional structure of a rotating object from a group of moving dots that are fixed relative to this rotating structure. Previous research has suggested that area V1 provides spatially localized motion measurements to MT, where they are integrated resulting in a coherent 3D interpretation (Bradley et al., 1998). However, it is not clear how external noise and attention may influence cortical responses. We used fMRI to measure the BOLD activity in visual cortex while subjects viewed structure-from-motion (SfM) stimuli of varying coherence in blocks. Subjects performed either a fixation task (unattended condition) or a shape recognition task (attended condition). Novel 3D shapes were generated using perturbations in spherical harmonics. External noise was induced by aligning 0%, 33%, 66%, or 100% of the moving dots with the structure, while the rest were shifted randomly a small amount away from the structural surface. Low-level stimulus features such as dot density, velocity vectors and static shape information were tightly controlled. We found that only intermediate and higher-level visual areas were significantly modulated by coherence level of the SfM stimuli. Responses in the early/mid-/higher-level visual areas were all influenced by attention. Visual areas hV4, LO1 and LOC showed interactions between attention and dot coherence. Responses of cortical areas further away from the retinal input showed greater dependence on the coherence level. Attention to the 3D structure also increased response dependence on coherence, and enlarged dynamic range of BOLD responses to variations in coherence.
Meeting abstract presented at VSS 2014
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