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Daniel D. Dilks, Chris I. Baker, Eli Peli, Nancy Kanwisher; Reorganization of visual processing in macular degeneration is not specific to the “preferred retinal locus”. Journal of Vision 2009;9(8):732. doi: 10.1167/9.8.732.
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Recent work has shown that foveal cortex, deprived of its normal bottom-up input as a result of macular degeneration (MD), begins responding to stimuli presented to a peripheral retinal location. However, these studies have only presented stimuli to the “preferred retinal location”, or PRL, a spared part of the peripheral retina used by individuals with MD for fixating, face recognition, reading, and other visual tasks. Thus, previous research has not yet answered a question critical for understanding the mechanisms underlying this reorganization: Does formerly foveal cortex respond only to stimuli presented at the PRL, or does it also respond to other peripheral locations of similar eccentricity? If foveal cortex responds to stimuli at PRL because the PRL has become the functional equivalent of the fovea (the “Functional Fovea” hypothesis), then foveal cortex will not respond to stimuli presented at other locations. On the other hand, if foveal cortex responds to stimuli at PRL because deprived cortex simply responds to any peripheral retinal input, independent of whether input at that retinal location has been chronically attended for months or years (the “Passive Reorganization” hypothesis), then foveal cortex will respond not only to stimuli at PRL, but also other peripheral locations of similar eccentricity. Using fMRI, we found clear activation of foveal cortex to stimuli presented at either the PRL or an iso-eccentric non-PRL location in two individuals with MD, supporting the Passive Reorganization hypothesis. This finding suggests that reorganization is driven by passive, not use-dependent mechanisms.
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