Abstract
Steadily presented, binocularly rivalrous dichoptic stimuli with multiple features can induce feature binding errors in the resulting percept (Hong & Shevell, 2009). This is consistent with rivalrous colors and forms being resolved separately (Sterling, 1901). However, many binocular V2 neurons are tuned to a combination of chromaticity and orientation (Gegenfurtner, 2003). The present study used dichoptic grating stimuli that could differ in both orientation and chromaticity to determine if the percept is resolved in binocular neurons driven by individual features or conjunctions of features. METHODS Three observers viewed dichoptic equiluminant chromatic square-wave gratings, swapped between the eyes at 3.75 Hz (interocular-switch rivalry). Two conditions were tested: rivalrous gratings differed in [1] only orientation (say, green vertical and green horizontal) or [2] both orientation and chromaticity (green vertical and red horizontal). If the resolution of ambiguity occurs in binocular neurons driven by an individual feature, such as orientation or color, condition [2] allows for misbound percepts (red vertical). If the percept is resolved by neurons tuned for feature conjunctions, misbound percepts should not be seen. Observers reported their percepts of the dichoptic stimuli by pressing buttons on a gamepad. RESULTS Interocular-switch rivalry in condition [1] did not evoke binocular rivalry; instead, the percept was the superimposition of the stimuli (a plaid). Interocular-switch rivalry, however, does not eliminate suppression: with the simple addition of the second chromaticity in condition [2], observers no longer perceived a plaid. Instead, with joint orientation and color rivalry in [2] the percept alternated between the two stimuli. A control experiment eliminated the possibility that this difference in [2] was due to a luminance artifact. All observers perceived only the orientation-color combinations presented in the stimuli, indicating that the resolution of ambiguity caused by interocular-switch rivalry occurs in binocular neurons following feature integration.
Meeting abstract presented at VSS 2017