Reducing crowding by weakening inhibitory lateral interactions in the periphery with perceptual learning

We investigated whether lateral masking in the near-periphery, due to inhibitory lateral interactions at early level of central visual processing, could be weakened by perceptual learning and whether learning transferred to an untrained higher level lateral masking known as crowding. The trained task was a contrast detection of a Gabor target presented in the near periphery (ie 4°) in the presence of co-oriented and coaligned high contrast Gabor flankers, with different target-to-flanker separations along the vertical axis varying from 2λ to 8λ. We found both suppressive and facilitatory lateral interactions at a target-to-flanker range (2λ–4λ and 8λ respectively) larger than in the fovea. Training reduces the suppression but does not increases facilitation. Most importantly, we found that learning reduces crowding, in addition to improving contrast sensitivity, but had no effect on VA. These results suggest a different pattern of connectivity in the periphery with respect to the fovea and a modulation of this connectivity by perceptual learning that, not only reduces low-level lateral masking, but reduces crowding. These results have important implications for rehabilitation of low-vision patients that must use peripheral vision to perform tasks, such as reading and refined figure-ground segmentation that normal sighted subjects perform in the fovea.