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Kuei-Po Chen, Chien-Chung Chen; Cortical activation for 3D shapes constructed from different depth cues. Journal of Vision 2006;6(6):253. doi: https://doi.org/10.1167/6.6.253.
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We investigated cortical responses to 3D shapes constructed from motion parallax, binocular disparity, and perspective cues with fMRI.
The 3D global shapes were horizontal sinewaves (0.1875 cyc/deg) modulated in depth. The local elements were elongated Gaussian bars (space constant 0.7′x20′). The motion cue had the bar elements moving horizontally with a velocity defined by a sinusoid function (maximum velocity: +/− 0.5 deg/s). The disparity cue had the disparities (maximum disparity +/− 0.15 deg) between corresponding bars in the left and the right eye images determined by a sinusoid function. The perspective cue had the bar elements with different orientation defined by a perspective algorithm.
We used a block design to measure differential BOLD activations between stimuli with either one or two depth cues and a control with no depth cue. For an attention control, the observer was instructed to respond when the color of the fixation point changed. The EPI image (TR=3000ms, TE=40ms, flip angle=90°) were acquired on a Bruker 3T scanner.
The middle occipital gyrus (MOG) and the right intraparietal sulcus (IPS) were activated by 3D shapes defined by any depth cues. The ventral occipital cortex was only activated for monocular depth cues. The MOG activation was expanded toward more anterior and dorsal regions when there were more one depth cue available. Our result implies that the stereopsis is mainly a function of the dorsal stream while processing monocular depth cues requires both ventral and dorsal streams.
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