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Lab Affiliation Marvin Chun - Visual Cognitive Neuroscience Lab |
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| Constructive nature of visual perception | |||
| Visual perception and memory are constructive processes. For example, when we scan the world, we are constantly updating scene representations, as well as making predictions about what we might see outside the view. It is fascinating how our visual system creates a continuous world with such multiple representations of our environment. Using fMRI, we demonstrate that scene-selective regions of the brain constructs a representation that integrates multiple views, and that is extrapolated from a current view. | |||
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To allow perception of a continuous world, cortical mechanisms extrapolate missing information with highly constrained predictions about the environment just beyond the edges of a view. Here, we report functional magnetic resonance imaging evidence for extrapolation of scene layout information beyond what was physically presented, an illusion known as boundary extension. Consistent with behavioral reports, we observed boundary extension for scene selective attenuation in the parahippocampal place area (PPA) and retrosplenial cortex (RSC), but no such extrapolation of object representations in the lateral occipital complex (LOC). These results demonstrate that scene layout representations are extrapolated beyond the confines of the perceptual input. Such extrapolation may facilitate perception of a continuous world from discontinuous views. |
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One of the biggest challenges for human visual system is to create a seamless continuous world from multiple snapshots. Mediating this ability, there are at least two scene-sensitive regions of the brain, the parahippocampal place area (PPA) and retrosplenial cortex (RSC). Whereas the PPA is sensitive to changes in viewpoint of the same scene (Epstein, Graham & Downing, 2003), RSC may encode a more abstract scene-based representation independent of specific viewpoint (Bar & Aminoff, 2003; Epstein & Higgins, 2006; Park et al., 2007). To directly test this hypothesis, we presented different snapshot views from panoramic scenes. These views overlapped with each other by only 30%, so that they represented clearly different views, but appeared to come from the same panoramic scene. Using fMRI adaptation, we tested whether the PPA and RSC treated these panoramic views as the same or different. Results demonstrate that the PPA and RSC play different roles in scene perception: the PPA focuses on selective discrimination of different views while RSC focuses on the integration of scenes under the same visual context. |
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Interactions between working memory and attention |
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| Although people have remarkable ability to perform more than one task at a time, some tasks are harder to combine than others. Understanding which tasks interfere with each other is important for understanding how to optimize human performance, and such studies can reveal the architecture of how information is processed in the brain. I am interested in studying what kind of tasks share similar processing mechanisms with each other. | |||
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Load theory predicts that concurrent working memory load impairs selective attention and increases distractor interference (N. Lavie et al., 2004). Here we present new evidence that the type of concurrent working memory load determines whether load impairs selective attention or not. Working memory load was paired with a same/different matching task that required focusing on targets while ignoring distractors. When working memory items shared the same limited-capacity processing mechanisms with targets in the matching task, distractor interference increased. However, when working memory items shared processing with distractors in the matching task, distractor interference decreased, facilitating target selection. We propose a specialized load account to describe the dissociable effects of working memory load on selective processing depending on whether the load overlaps with targets or with distractors. |
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