Facilitation of contrast detection in near-peripheral vision

2 AbstractPurpose: The study investigated whether perceptual learning (PL) of a task consisting in detecting a low contrast Gabor patch flanked above and below by high contrast Gabor patches presented monocularly in the preferred retinal locus (PRL) of patients with macular degeneration (MD), improved their residual visual functions. Method:We measured contrast detection thresholds using both a Yes/No task (three MD patients and three controls) and a temporal two-alternative forced-choice task (2AFC; four MD patients and three controls).Results: Both tasks produced a significant improvement in contrast sensitivity for the trained target.However, only in the case of the temporal-2AFC this improvement depended on the target-toflankers distance. Furthermore, in both tasks PL improved visual acuity but with the temporal-2AFC task we found a higher degree of generalization of the training to untrained stimuli and tasks.In fact, we found a reduction of the crowding effect and an improvement of the contrast sensitivity for untrained spatial frequencies.Although PL is more effective with a temporal-2AFC task, it is also present with a Yes/No task, suggesting that PL reflects sensory enhancement, rather than improvement in decision mechanisms.Most importantly, follow-up tests on MD patients showed that PL effects were retained between four and eight months, suggesting PL induced long-term neural plasticity in the visual cortex. Conclusion:The results show for the first time that PL with a collinear configuration has strong, non-invasive and long lasting rehabilitative potential to improve vision in the PRL of patients with central vision loss.3

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“…This confirms the results of Giorgi et al (2004) that a temporal-2AFC task is a suitable procedure to measure collinear facilitation.…”

Section: Discussionsupporting

confidence: 89%

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

Maniglia

Pavan

Sato³

et al. 2016

RNN

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“…If we compare another similar condition we used to that of Shani and Sagi (2005) (i.e., 4 cpd and 6k [present study] vs. 4 cpd and 4k [Shani & Sagi, 2005]), the difference in contrast thresholds is reduced for the collinear condition (7%) but it is almost the same for the orthogonal condition (4%). Similarly, Giorgi et al (2004) measured peripheral collinear facilitation for a range of eccentricities and target-to-flankers distances with a temporal 2AFC. They reported a contrast threshold reduction of $0.1 log units already at 4k for 2°, 4°and 6°of eccentricity.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast to Lev and Polat (2011) and our previous study (Maniglia et al, 2011) we avoided the yes-no task for two main reasons, because: (i) it seems more suitable for measuring fillingin than collinear facilitation (Lev & Polat, 2011;Polat & Sagi, 2007), and (ii) as Giorgi et al (2004) reported, collinear facilitation in the periphery can be found with a temporal but not spatial twoalternative forced choice (2AFC). Probably because in the spatial 2AFC subjects are forced to attend competing stimulus configurations, reducing the facilitation.…”

Section: Introductionmentioning

confidence: 99%

The effect of spatial frequency on peripheral collinear facilitation

2015

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The detection of a Gabor patch (target) can be decreased or improved by the presence of co-oriented Gabor patches (flankers) having the same spatial frequency as the target. These phenomena are thought to be mediated by lateral interactions. Depending on the distance between target and flankers, commonly defined as a multiple of the wavelength (λ) of the carrier, flankers can increase or decrease a target's detectability. Studies with foveal presentation showed that for target-to-flankers distances<2λ contrast thresholds for the central target increase, while for target-to-flankers distances>3λ contrast thresholds decrease. Earlier studies on collinear facilitation at the near-periphery of the visual field (4° of eccentricity) showed inconsistent facilitation (Shani & Sagi, 2005, Vision Research, 45, 2009-2024) whereas more recent studies showed consistent facilitation for larger separations (7-8λ) (Maniglia et al., 2011, PLoS ONE, 6, e25568; Lev & Polat, 2011, Vision Research, 51, 2488-2498). However, all of these studies used medium-to-high spatial frequencies (3-8 cpd). In this study we tested lower spatial frequencies (1, 2, and 3 cpd) with different target-to-flankers distances. The rationale was that near-peripheral vision is tuned for lower spatial frequencies and this could be reflected in collinear facilitation. Results show consistent collinear facilitation at 8λ for all the spatial frequencies tested, but also show collinear facilitation at shorter target-to-flanker distance (6λ) for the lowest spatial frequencies tested (1 cpd). Additionally, collinear facilitation decreases as spatial frequency increases; opposite to the findings of Polat (2009, Spatial Vision, 22, 179-193) in the fovea, indicating a different spatial frequency tuning between foveal and peripheral lateral interactions.

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“…Since Polat & Sagi (1993) first demonstrated both facilitation and suppression with such an arrangement, a multitude of spatial (Polat & Sagi 1994;Polat 2009;Polat et al 1998;Zenger-Landolt & Koch 2001;Mizobe et al 2001;Freeman et al 2001;Woods et al 2002;Freeman et al 2004;Giorgi et al 2004;Polat et al 2005;Polat & Sagi 2007;Shani & Sagi 2005;Huang et al 2006;Huang & Hess 2007;Huang et al 2012;Huang & Hess 2008;Sterkin et al 2008;Katkov & Sagi 2010;Wu & Chen 2010;Kéita et al 2011;Lev & Polat 2011;Jachim et al 2015) and temporal (Tanaka & Sagi 1998;Polat & Sagi 2006;Cass & Alais 2006;Huang & Hess 2008;Sterkin et al 2009;Li et al 2010;Sterkin et al 2012) combinations of target and flanker designs have been developed.…”

Section: Introductionmentioning

confidence: 99%

Individual differences in the dynamics of collinear facilitation?

2017

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Collinear facilitation refers to the increase in sensitivity found for a target when aligned between nearby, brighter flankers. Many studies have explored the spatial and temporal aspects of this arrangement, and there is a consensus that two mechanisms could be responsible for this phenomenon; lateral excitation within V1 and extra-striate feedback to V1. There is some debate as to whether facilitation can still occur if the target is presented before the flankers, a manipulation known as backward masking, which could rely on feedback to V1. We shed light on this debate by using forward, simultaneous and backward masking with a relatively large sample of 26 participants.We used short stimulus presentation times (35 ms) and a range of SOAs (stimulus onset asynchronies) (-70, -35, 0, 35 and 70 ms) in order to isolate any feedback facilitation that may occur.We found that collinear facilitation occurred with forward masking (+ve SOAs) in all participants.However, facilitation with backward masking (-ve SOAs) only occurred in 54% of participants. We present a basic model of facilitation that simulates the results of our experiment and could account for differences between previous studies. The model indicates that facilitation with backward masking arises primarily from feedback excitation. Our findings suggest that both lateral connectivity and extra-striate feedback contribute to target facilitation, but in fundamentally different ways and that feedback may be significantly reduced in some participants.2

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Facilitation of contrast detection in near-peripheral vision

Cited by 32 publications

References 28 publications

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

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

The effect of spatial frequency on peripheral collinear facilitation

Individual differences in the dynamics of collinear facilitation?

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