Motion processing in visual cortex of maculopathy patients
Previous studies on animal models suggested that visual areas involved in motion processing could undergo important cortical reorganizations following retinal damages. This could have major implications for patients suffering from macular degeneration (MD), the leading cause of vision loss in older adults. Here, we performed fMRI recordings in a group of maculopathy patients (including individuals suffering from age-related macular degeneration or from Stargardt's Disease) and a control group to characterize the motion processing cortical network in MD patients and determine whether this network undergoes significant large-scale reorganisations following the onset of the scotoma. We used an experimental protocol based on random-dot kinematograms (RDKs) classically employed to characterize motion-selective areas in the brain. To ensure that the visual information processed by the two groups was equivalent, the visual field in each control participant was masked using an artificial scotoma directly derived from clinical measurements in their paired patient. We found that in MD patients, translational motion elicited significant and robust activations in a restricted cortical network which included the human V5/MT+ complex (hMT+), areas V3A and V6 and a portion of primary visual areas (V1, V2 and V3) connected to peripheral vision. Importantly, the same patterns of responses were also observed in control participants. Moreover, the extent and strength of activation within these motion-selective areas did not differ significantly between the two groups. Altogether, these results suggest that in humans, the motion-selective network does not undergo significant large-scale cortical reorganizations following the onset of MD.