Large-scale cortical reorganization is absent in both juvenile and age-related macular degeneration

Abstract

Introduction. Although there is evidence that human visual cortex is capable of reorganization with congenital central retinal lesions, it is controversial whether this capability is maintained later in life. We used fMRI to study visual cortical responses in a relatively large number of patients with macular degeneration (MD).

Methods. To determine whether reorganization might be age-dependent, we compared patients from two groups: 8 with age-related MD (mean age 80+/-6) and 8 with juvenile MD (Stargardt disease; mean age 34+/-10). Patients were tested at least one year after the onset of bilateral central scotomata. Nidek microperimetry was used to select patients with an established preferred retinal locus (PRL) and no foveal sparing. PRL coordinates were then used to center stimuli on the fovea of the tested eye. Each group was compared with a similar number of age-matched controls. Standard retinotopic mapping checkerboard stimuli were presented to all participants, and central lesions were also simulated in controls. Cortical responses were compared in three anatomically defined regions of interest (ROIs) within V1: (1) LPZ, the expected “lesion projection zone” in MD patients, located at the occipital pole, (2) IPZ, representing eccentric intact retina in patients, located anteriorly in the calcarine sulcus, and (3) a baseline region where no visually elicited activity was predicted, located in non-occipital cortex. Results. Signal amplitudes for the three ROIs were compared using a multivariate ANOVA across groups. In controls, cortical responses in both LPZ and IPZ were significantly different from baseline. In patients and in simulated lesion controls, cortical responses in IPZ, but not in LPZ, differed significantly from baseline. There was no significant difference in responses between the two patient age groups. Conclusion. Large-scale cortical reorganization is not evident in patients with either juvenile or age-related macular degeneration.

Footnotes

 Medical Research Council, UK.