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Abstract:
This study investigates how the visual system constructs representations of 3-D shape from a variety of cues using fMRI in anesthetized monkeys. A variety of computer-generated 3-D objects (e.g., geometrical shapes, faces, and other organic forms) defined by shading, random dots, texture elements, silhouetted, or as a wire frame were presented either statically, dynamically (i.e., rotating), or with stereo disparity. Control stimuli included constructed objects with scrambled cue gradients. Such stimuli contained the same local information as the original objects, but the disruption of the cue gradient across the image led to a loss of an impression of depth. Spatially resolved BOLD contrast-based functional images of monkey visual cortex were obtained using a hi-field (4.7 T) scanner and multi-shot, multi-slice, gradient-recalled, echo-planar imaging (EPI) sequences to image the brain (voxel volume, 0.5 × 0.5 × 2 mm3; TE=20 ms; TR=750 ms; FA=50 deg). Results showed significant activation in early visual areas, motion areas, and parts of the STS and IT cortex, suggesting involvement of multiple stages of processing of 3-D form starting in area V1 and continuing into the most anterior portions of the temporal lobe.
