The Underlying Mechanism of Binocular Surround Modulation

Abstract

The detection abilities of a visual target can be improved or impaired by its surround stimulus which is termed surround modulation The strengths or signs of the modulation effects depend on the properties of the surround mask and target location In response we systematically measured the detection threshold of a target (horizontal Gabor 2 cpd) with respect to various surround types at foveal and parafoveal (2 7 degrees) locations In Experiment 1 we investigated whether the modulation occurred before or only after the binocular integration stage and its correspondence orientation tuning properties Our results showed the surround modulation occurred before the binocular integration stage with involvement of interocular suppression at fovea while it occurs after binocular summation with tuning for orientation at parafovea In Experiment 2 we investigated the processing order for overlay suppression and surround modulation by using plaid surround Our results showed the plaid mask formed before the binocular integration at foveal viewing condition while it formed after binocular integration and suppressed the target detection ability before the plaid was formed at parafovea In Experiment 3 the binocular target instead of the monocular target was used to clarify the influence of feature matching between two eyes in surround modulation effects Our results showed the surround modulation reduced owing to binocular-matched stimuli only at foveal viewing condition but not at parafovea Our results suggested the underlying mechanism of surround modulation was different at foveal and parafoveal locations At foveal location the surround modulation was dominated by the interocular suppression occurring before the binocular integration stage At parafoveal location the interocular surround modulation occurred before monocular surround modulation processing

Date of Award	2018 Jan 25
Original language	English
Supervisor	Pi-Chun Huang (Supervisor)