Abstract
PurposeStudies concerning the effects of peripheral retinal degeneration on visual cortical structure and function are scarce. Our work aimed to determine the effect of peripheral retinal dystrophy caused by Retinitis Pigmentosa on brain function and structure using magnetic resonance imaging, taking into account the effect of the preserved visual field extent and the disease onset age.MethodsWe included thirteen patients and twenty‐two matched controls. We analyzed cortical responses under attentional demands and passive viewing conditions while presenting a visual stimulus covering the central and paracentral visual field. Responses were studied in the visual cortical areas (V1, V2 and V3) and also in two cortical regions of interest corresponding to the preserved and the damaged visual field. The cortical thickness of visual areas was also measuredResultsWe found that cortical visual responses under attentional demands were increased in patients with larger degeneration of visual field. Moreover, activation during the task condition was increased for patients in both cortical regions corresponding to the preserved and the damaged visual field, specifically in patients with severe visual field loss. These findings were observed in presence of preserved visual cortical structure.ConclusionsWe conclude that Retinitis Pigmentosa patients have enhanced visual attentional modulation despite their retinal degeneration, while cortical structure remains intact (with an relative increase in V2 thickness in patients with RP in early stages). The unmasking of feedback signals from higher level visual regions involved in attentional processes may explain the increased cortical responses. These findings are relevant in the context of the design of strategies for treating retinal diseases.
Highlights
Human studies concerning the effects of peripheral retinal loss on adult visual cortical structure and function are scarce
No statistically significant differences were found between the left and right eyes within groups for visual acuity (RP Z = 1 33, NS and control Z = 1 41, NS), average retinal thickness (RP Z = −0 84, NS and control Z = −0 88, NS), retinal nerve fiber layer (RNFL) thickness (RP Z = 0 00, NS and control Z = −0 07, NS), visual field deficit volume (RP Z = −1 24, NS and control Z = −0 28, NS), and visual field extent (RP Z = −1 18, NS; controls have a constant visual field extent equal to 48 deg corresponding to the maximum diameter covered by our static perimetry) [6]
We investigated whether visual cortical responses in a disorder of peripheral vision are related to recruitment of attentional mechanisms
Summary
Human studies concerning the effects of peripheral retinal loss on adult visual cortical structure and function are scarce. Previous studies have mainly addressed central retinal disorders such as macular degeneration or other hereditary retinal dystrophies and diseases such as glaucoma [1,2,3]. Peripheral and central visual information is differentially routed in the brain [4, 5]. Neural adaptation mechanisms might differ when central or peripheral visual degeneration occurs. We found evidence for visual retinotopic reorganization in RP (peripheral regions responding to more central representations) [6]. It is important to assess the impact of peripheral retinal loss on visual
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