Evidence for visual cortical plasticity in retinitis Pigmentosa

Abstract

AbstractPurpose: Neural plasticity upon visual loss remains a very controversial phenomenon. We asked how the changes in peripheral visual input in adult Retinitis Pigmentosa patients would impact the stability versus plasticity of neuronal population receptive fields in early visual areas.Methods: A total of 37 participants were recruited. The Retinitis Pigmentosa group (RP) included 12 patients with RP. The full‐field Control group (FFCnt) included 13 healthy participants that performed the original protocol (as the RP group); and an artificial scotoma Control group (ASCnt) (n = 12). Population Receptive Field (pRF) fMRI paradigms were used at 3 Tesla. The maximum field of view was 23° × 30°. The stimuli used for pRF estimation consisted in conventional single, 45° counter‐clockwise rotating wedge and expanding ring stimuli with a high‐contrast (~100%) flickering (8 Hz) checkerboard pattern. To resolve chronic from acute adaptive effects we performed an artificial scotoma experiment, in an independent control group.Results: The general increase of pRF size on eccentricity was found in both Retinitis Pigmentosa and control individuals as expected. Interestingly, in RP, the regression slopes of pRF size and eccentricity in V1 and V2 seem to collapse in RP patients, in contrast with controls. Analysis of the regression lines adjusted to the mean pRF size along eccentricity in the calcarine sulcus of RP and matched ASCnt showed a significant difference between slopes (F(1,296) = 15.01, p < 0.001), corresponding to a group difference in pRFs size in more peripheral locations, suggesting plasticity. Artificial scotoma pRF mapping showed no evidence for rapid adaptation.Conclusions: We found evidence for long term visual plasticity in adult Retinitis Pigmentosa patients as demonstrated by increased size of peripheral neuronal population receptive fields in early visual areas, which could be explained by rapid adaptation mechanism.