Preserved retinotopic brain connectivity in macular degeneration.
PURPOSE
The eye disease macular degeneration (MD) is a leading cause of blindness worldwide. There is no cure for MD, but several promising treatments aimed at restoring vision at the level of the retina are currently under investigation. These treatments assume that the patient's brain can still process appropriately the retinal input once it is restored, but whether this assumption is correct has yet to be determined.


METHODS
We used functional magnetic resonance imaging (fMRI) and connective field modelling to determine whether the functional connectivity between the input-deprived portions of primary visual cortex (V1) and early extrastriate areas (V2/3) is still retinotopically organised. Specifically, in both patients with juvenile macular degeneration and age-matched controls with simulated retinal lesions, we assessed the extent to which the V1-referred connective fields of extrastriate voxels, as estimated on the basis of spontaneous fMRI signal fluctuations, adhered to retinotopic organisation.


RESULTS
We found that functional connectivity between the input-deprived portions of visual areas V1 and extrastriate cortex is still largely retinotopically organised in MD, although on average less so than in controls. Patients with stable fixation exhibited normal retinotopic connectivity, however, suggesting that for the patients with unstable fixation, eye-movements resulted in spurious, homogeneous signal modulations across the entire input-deprived cortex, which would have hampered our ability to assess their spatial structure of connectivity.


CONCLUSIONS
Despite the prolonged loss of visual input due to MD, the cortico-cortical connections of input-deprived visual cortex remain largely intact. This suggests that the restoration of sight in macular degeneration can rely on a largely unchanged retinotopic representation in early visual cortex following loss of central retinal function.
['Haak|Koen V|KV|', 'Morland|Antony B|AB|', 'Rubin|Gary S|GS|', 'Cornelissen|Frans W|FW|']
D000328:Adult D005133:Eye Movements D005260:Female D006801:Humans D008268:Macular Degeneration D008279:Magnetic Resonance Imaging D008297:Male D008875:Middle Aged D012160:Retina D014793:Visual Cortex D014794:Visual Fields D014796:Visual Perception D055815:Young Adult
macular degeneration fMRI connective field modelling cortical lesion projection zone retinotopy