Abstract
Does the organization of receptive fields throughout the ventral visual hierarchy constrain perception? Receptive fields are known to get progressively larger at each successive stage of visual processing, with large receptive fields in anterior regions (FFA/PPA) being primarily confined within a single hemifield. From this we predicted that performance on a behavioral task with high-level items (faces/scenes) would be better when stimuli were presented across hemifields compared to when they were presented within a hemifield. This is because during within hemifield presentation, multiple stimuli will fall within the same receptive fields and mutually interfere. Meanwhile, since receptive fields in lower-level regions (V1-V4) are too small to encompass multiple items, we predicted there would be no hemifield effect with low-level categories. In Experiment 1, participants performed a change detection task with three high-level categories: faces, scenes, and objects. As predicted, performance was better when stimuli were presented across hemifields than when presented within a hemifield (p<0.05 in all three cases). To test if this effect is due to the arrangement of high-level receptive fields or the existence of independent pools of attention in each hemifield, we replaced the high-level categories with two low-level categories (color/orientation) in Experiment 2. The size, location, and presentation conditions between the experiments were identical; only the stimuli differed. In this case, no hemifield effect was seen for either colors (p=0.45) or orientations (p=0.32). Finally, in Experiment 3, we found a hemifield effect with high-level objects when stimuli were presented simultaneously during the initial presentation display (p<0.05), but not when stimuli were presented sequentially (p=0.61). This suggests that within hemifield interference occurs primarily during stimulus encoding. Together, these results suggest that the organization of high-level ventral visual regions into spatial maps constrains the simultaneous perception of high-level, but not low-level, visual categories.
Meeting abstract presented at VSS 2013