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Menaka Samanmali Malavita, Trichur Vidyasagar, Allison Maree McKendrick; Eccentricity dependency of centre-surround orientation interactions on suppression of contrast detection. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4220.
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© ARVO (1962-2015); The Authors (2016-present)
Perceptual surround suppression has been extensively studied as an analogue of cortical excitatory and inhibitory mechanisms in humans. Contrast detection thresholds of a central target can be either facilitated or suppressed depending on the contrast, orientation and spatial frequency of the surround. However, such effects on surround suppression have been rarely studied in the visual periphery. The specific purpose of this study was to study the orientation dependency of centre-surround interactions outside of the fovea. Specifically, we hypothesised that centre-surround orientation interactions in peripheral vision depend not only on the relationship of the orientation between the centre and surround but also on the retinotopic location of the centre-surround stimulus.
Contrast detection thresholds were estimated for radially and tangentially oriented centre targets with parallel, oblique (45°) and orthogonal surrounding annuli in nasal, inferior and infero-temporal visual field locations at 6° and 15° eccentricities. Two experienced and one naïve (mean age= 27.3 years) psychophysical observers participated in the study. Suppression ratio was calculated as the ratio between the detection threshold with a surround and without a surround.
We find that at 6° and for the parallel centre-surround orientation, greatest suppression is seen for the horizontal compared to vertical configuration (RM-ANOVA; df = 1, p=0.006) and this effect disappears at 15° (RM-ANOVA; df =1, p=0.29). There was no bias for orientation at 15° (RM-ANOVA; df =1, p=0.19). Further, the magnitude of suppression was dramatically reduced with 45° centre-surround orientation difference on a radially oriented centre but not for a tangentially oriented centre, indicating a difference in the orientation tuning bandwidth between these conditions.
We suggest this change in the orientation anisotropy with eccentricity reflects a link between surround suppression and visual field retinotopy. Orientation tuning properties may be different for centre-surround orientations with respect to visual field location and eccentricity.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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