This project extends the understanding of higher-level visuo-spatial processing by applying a resource-based cognitive theory, called capacity theory, to the large-scale networks that subserve visuo- spatial processing. The goal is to relate the psychological activity postulated at the cognitive level to brain-level activity, as measured by functional Magnetic Resonance Imaging (fMRI). The proposed research uses fMR imaging to investigate the contributions of regions associated with two systems that subserve higher-level visual processing, the dorsal (""""""""where"""""""") and ventral (""""""""what"""""""") systems. The main hypothesis is that the two systems interact when the task demand is high relative to the resource supply. The tasks involve object recognition and visuo-spatial processing, and demand is manipulated by parametrically varying the complexity of the task. The theory predicts that the increase in demand will produce monotonic increases in fMRI-measured activation in both systems. Other studies examine the relation between the neural systems that subserve imaginal processing and those that subserve perceptual processing, including the perception of apparent and real motion. The main hypothesis is that while the same neural areas will be activated, there will be quantitative variation in the volume of fMRI- measured activation depending on whether the task is imaginal or perceptual. Specifically, the prefrontal and parietal areas will have a higher volumes of activation in imagery tasks, while the occipital and middle temporal areas will have higher volumes of activation in comparable perceptual tasks. Five sets of experiments test the generality of the theoretical claim that the volume of brain activation is a function of the task demand, rather than solely a function of the type of computation being performed. One health-related implication is that the experimental tasks are adaptations of clinically-used tasks, and hence, the theoretical analysis relates a cognitive model to clinical tasks and neural functioning. The fMRI paradigms also provide a tool for non-invasive assessments of neural function that has wide applicability in therapeutic, clinical and medical settings.
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