Abstract
Interocular suppression has been demonstrated in multiple binocular tasks. However evidence for interocular enhancement has been elusive, because, in the normal visual system, it is concealed by the strong interocular suppression. Interocular enhancement was first exposed in a study on amblyopic binocular vision (Ding, Klein & Levi 2013b) where the interocular suppression from the non-dominant eye to the dominant eye is almost absent, thus revealing interocular enhancement. For normal binocular vision, adding interocular enhancement to a gain-control model (Ding-Sperling model, Ding & Sperling 2006) results in significant improvement in model fitting in binocular phase and contrast combination tasks (Ding, Klein & Levi 2013a), and in binocular contrast discrimination (Ding & Levi 2016). In the present study, we examined how normally sighted observers combine slightly different orientations presented to the two eyes. The stimuli were briefly presented (80 ms) Gabor patches (3 cpd) presented to the two eyes, which differed in both orientation and contrast. We used a signal-detection rating method to estimate the perceived orientation. We tested three orientation differences (10, 15 and 20 degrees), four base contrasts (10, 20, 40, and 60%) and seven interocular (dichoptic) contrast ratios (0.25, 0.5, 0.75, 1, 1.33, 2, and 4). We found that the interocular suppression decreased when the base contrast increased, contradicting the prediction (more suppression at a higher contrast level) of the Ding-Sperling model. Our modeling showed that interocular enhancement is needed to neutralize the effect of interocular suppression when the base contrast increased. By adding interocular enhancement to the Ding-Sperling model, the modified model successfully accounted for whole data set. Combined with interocular suppression, interocular enhancement appears to play an important role in binocular vision.
Meeting abstract presented at VSS 2017