Researchers expect that this study will determine whether cortical reorganization occurs in adults who develop macular degeneration and, if so, whether the reorganization facilitates improved vision.
While cortical reorganization occurs in congenitally blind people, enabling them to develop compensatory auditory, verbal, and memory functions, clinicians do not know whether functional reorganization occurs in adults who lose vision due to macular degeneration. This disease obliterates vision in the center of the gaze and produces partial damage to peripheral vision. Since the central visual field has much greater cortical representation compared to the peripheral regions, the ability to judge the shapes of patterns (such as letters) is better in the center of the gaze than in the visual periphery. The researchers hypothesize that, if cortical reorganization does occur in macular degeneration, it will be directed by a “remapping” principle. According to this remapping concept, cortical regions that normally map to central vision will instead map to peripheral vision.
Using fMRI, the investigators will determine patterns of activity throughout the brain when participants watch a visual stimulus inside the scanner. They then will test the remapping hypothesis by consistently changing the position of the visual image on the screen and observing cortical activation patterns. Additionally, the investigators will determine whether, when patients gaze off center, this preferred retinal location is over-represented in the visual cortex and is accompanied by better accuracy in that visual region of the grain.
Significance: The study is anticipated to provide insight into brain plasticity that might lead to better rehabilitation methods for people with macular degeneration that enables them to maximize visual capacity.