Human visual perception relies on both selective and constructive neural mechanisms to organize and to interpret visual information. The selectivity of perception can be seen in binocular rivalry, during which each eye views a different monocular pattern. Under these conditions, perception selectively alternates between one monocular image versus the other image every few seconds. Conversely, the constructive nature of perception may be best exemplified by perceptual filling-in of the blind spot in which vivid impressions occur in a visual location that lacks any input. Exactly how the brain mediates these complementary processes of perceptual selection and construction remains poorly understood. This project will use functional magnetic resonance imaging (fMRI) to investigate the neural basis of binocular rivalry and perceptual filling-in within human visual cortex. Our central hypothesis is that selective perception during rivalry and constructive perception during filling-in involve separate neural mechanisms that operate at different levels of the visual system. To investigate these issues, we have developed special behavioral and fMRI techniques to localize the cortical representation of the blind spot quickly and reliably, in previous studies, we have shown that fMRI activity in the monocular VI representation of the blind spot is tightly linked to perceptual awareness during rivalry, suggesting that rivalry results from early competition between monocular VI neurons. In contrast, when we stimulate the retinal region immediately surrounding the blind spot, we find evidence of a """"""""hole"""""""" in visual activity in Vi but not in V2, perhaps suggesting that perceptual filling-in occurs in higher visual areas such as V2. The proposed research will characterize the neural mechanisms and visual areas responsible for rivalry and filling-in. More important, it will address scientific debates regarding whether: i) binocular rivalry arises from interocular competition versus pattern competition, and ii) perceptual filling-in arises from active neural completion versus passive remapping of visual inputs. This project will advance our knowledge of the neural organization of selective and constructive mechanisms in human visual perception. Such research is important given that vision serves as a primary sense for acquiring information from the environment to guide judgments and actions. The proposed studies will not only address the neural basis of human visual perception but will also inform research on visual dysfunctions and neurological disorders, including strabismus, amblyopia (suppressed vision in one eye), and the neural consequences of visual-field loss resulting from retinal or cortical injury.
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