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Teng Leng Ooi, Chao Han, Maureen Daley Plaumann, Zijiang J He; Large-field binocular suppression mediated by naso-temporal asymmetry and contour processing. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1951.
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© ARVO (1962-2015); The Authors (2016-present)
Eyes misalignment in strabismus causes vast binocular corresponding areas to be stimulated with dissimilar images. Presumably, this abnormal condition triggers binocular rivalry (BR), which leads to pathological suppression. But the assumption raises the fundamental question of how the preference for global interocular suppression is determined. Current knowledge is insufficient as it is mainly obtained from BR research using small to medum size stimuli (1o-10o). Here, we measured BR with larger scale displays to simulate the full-field mismatch of strabismus.
The counterbalanced BR stimuli comprised vertical and horizontal red-black and blue-black 1cpd sinusoidal gratings. The peak blue luminance was 2.43 cd/m2; the red was 2.14, 4.30, or 10.5 cd/m2. Test 1 had a full-field stimulus spanning the display screen (56ox33o) with a central nonius fixation. Test 2 was similar but with a smaller stimulus size (24ox33o). Tests 3 and 4 were similar to test 2, but were placed respectively, to the right and left of the fixation. As large BR stimuli produce piecemeal percepts, we measured the BR percept at the edges of the stimuli, as the fixed spatial reference. We thus asked subjects (n=8) to detect if the blue grating was seen at the stimulus’ right or left edge. The stimulus duration (400 ms) was brief enough to prevent BR alternation but sufficiently long for BR to occur.
We found the full-field stimulus led to 99.9% mean dominance of the ipsilateral eye in the temporal visual field (p<0.000001, t-test). The dominant edge was usually perceived as a distinct strip. This trend held for the smaller central stimulus (test 2) (97.2% dominance, p<0.00001). Together, they suggest conformity with the naso-temporal asymmetry notion of inhibition. However, complicating this notion, we also found that the left eye dominated at the left edge while the right eye dominated at the right edge in tests 3 (93.1% dominance, p<0.00001) and 4 (91.8% dominance, p<0.0001), where the stimuli were presented, respectively, to the right and left visual fields.
Our findings indicate BR dominance of large stimulus spanning both the right and left visual fields observes the naso-temporal asymmetry rule. But when the stimulus is restricted to either the right or left field, the dominance preference is influenced by the boundaries of the stimulus, suggesting the impact of cortical contour processing.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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