Reducing Crowding by Weakening Inhibitory Lateral Interactions in the Periphery with Perceptual Learning

Abstract

We investigated whether lateral masking in the near-periphery, due to inhibitory lateral interactions at an 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 contrast detection of a Gabor target presented in the near periphery (4°) in the presence of co-oriented and co-aligned high contrast Gabor flankers, which featured different target-to-flankers separations along the vertical axis that varied from 2λ to 8λ. We found both suppressive and facilitatory lateral interactions at target-to-flankers distances (2λ - 4λ and 8λ, respectively) that were larger than those found in the fovea. Training reduces suppression but does not increase facilitation. Most importantly, we found that learning reduces crowding and improves contrast sensitivity, but has no effect on visual acuity (VA). These results suggest a different pattern of connectivity in the periphery with respect to the fovea as well as a different modulation of this connectivity via perceptual learning that not only reduces low-level lateral masking but also reduces crowding. These results have important implications for the rehabilitation of low-vision patients who must use peripheral vision to perform tasks, such as reading and refined figure-ground segmentation, which normal sighted subjects perform in the fovea.

Perceptual learning leads to long lasting visual improvement in patients with central vision loss

“…Moreover, peripheral collinear suppression appears to be modulated by PL. Specifically, PL reduces suppression but does not increase facilitation (Maniglia et al, 2011). The PL effect with eccentric presentation transfers to untrained higher spatial frequencies and reduces the crowding effect (i.e., the inability of discriminating objects or letters in clutter; Levi, 2008;Pelli & Tillman, 2008).…”

“…One of the most efficient approaches consists in a contrast detection task for a low contrast Gabor patch flanked above and below by high contrast Gabor patches (Polat et al, 2004;Polat, 2009;Maniglia, Pavan, Cuturi, Campana, Sato, & Casco, 2011;Casco, Guzzon, Moise, Vecchies, Testa, & Pavan, 2014). For foveal stimuli, it has been found that collinear flankers placed at a distance of 3-4 times the wavelength of the target Gabor's carrier (λ) enhance target detection (Polat & Sagi, 1993, 1994a, 1994b, thus producing facilitation (i.e., lower contrast detection thresholds).…”

“…PL with collinear configuration increases facilitation, reduces suppression (Polat & Sagi, 1994b) and transfers to untrained, higher-level visual abilities such as VA and CSF (see Polat, 2009 for a review). In addition, there is recent psychophysical evidence of collinear facilitation in the near periphery of the visual field (4° of eccentricity), at a target-to-flankers distance larger than in the fovea (between 7λ and 8λ) (Maniglia et al, 2011;Maniglia, Pavan, & Trotter, 2015), suggesting that the spatial range of facilitatory lateral interactions is increased in the near periphery. Moreover, peripheral collinear suppression appears to be modulated by PL.…”

“…In the present study MD patients and controls were trained in a contrast detection task using a collinear configuration. This procedure has been shown to probe neural plasticity (Polat & Sagi, 1994b) and producing significant generalization to other visual abilities not previously trained (e.g., VA, CFS, crowding), both in fovea and in the near periphery of the visual field (Polat et al, 2004;Tan & Fong, 2008;Polat, 2009;Maniglia et al, 2011;Casco et al, 2014). In particular, the aim of the present study was to investigate whether training contrast detection of a low-contrast target flanked by collinear high contrast flankers can improve untrained high-level visual abilities in MD patients.…”

The application of online transcranial random noise stimulation and perceptual learning in the improvement of visual functions in mild myopia

“…In the past decade, PL has started to be considered a useful tool for improving visual functions in clinical populations due to its generalizable effects. In fact, under specific conditions, PL is able to transfer to other stimuli, tasks and circumstances (Camilleri, Pavan, Ghin, Battaglini, et al, 2014;Jeter, Dosher, Petrov, & Lu, 2009;Liu & Weinshall, 2000;Maniglia, et al, 2011;McGovern, Webb, & Peirce, 2012;Webb, Roach, & McGraw, 2007;Xiao, et al, 2008;Zhou, et al, 2006), making it a practical tool that may yield potential benefits for various types of visual impairments. In general, most studies point to a localized increase in processing efficiency in V1 following practice on a visual perceptual task.…”