Abstract
We previously reported large-scale reorganization of visual processing (i.e., activation of “foveal” cortex by peripheral stimuli) in six individuals with extensive retinal lesions, and complete loss of foveal input from macular degeneration (MD) (Dilks et al., 2009; Baker et al., 2008; Baker et al., 2005). However, we found no evidence for such reorganization in two other MD individuals with extensive retinal lesions but some foveal sparing (Baker et al., 2007), and hypothesized that large-scale reorganization of visual processing is dependent on complete foveal loss of input from MD. Here we applied the strongest test of this hypothesis: we investigated one of the MD individuals, who originally had some foveal sparing and exhibited no reorganization, but now has lost all foveal function. We predicted that if reorganization of visual processing arises only in MD individuals with complete foveal vision loss, then we will see reorganization in this individual only after losing all foveal function, and not before. Indeed, we found reorganization in the same individual only after complete foveal vision loss. We conclude that large-scale reorganization of visual processing occurs only in the complete absence of functional foveal vision in individuals with MD.
NIH grant EY016559 (NK), Kirschstein-NRSA EY017507 (DDD).