Abstract
AIM: To determine whether audition alters the temporal dynamics of binocular rivalry (BR) and flash suppression (FS). METHODS: Exp.1: Concentric gratings (2.7deg diameter, 2.4cpd) loomed or receded at 1Hz or 3Hz. Subjects monitored BR alternations in three 8min trials for three conditions: 1Hz looming/1Hz receding, 1Hz looming/3Hz receding, and 3Hz Looming/1Hz receding. These were paired with either: no sound, a looming tone matching the looming grating, or a receding tone matching the receding grating. Exp.2: The same concentric gratings were used in a FS paradigm (changing at 2Hz). SOA thresholds for complete suppression of lead stimulus by ‘flash’ stimulus were measured under auditory and no-sound conditions. Sounds included: constant tones, ‘beep’ warning tones, looming/receding and expanding/contracting tones.
RESULTS: Exp.1: 1 and 3Hz looming gratings predominated over receding gratings. Adding auditory looming (1 or 3Hz) increased looming predominance, relative to no-sound. Receding sounds did not influence predominance. Exp.2: Expanding ‘flash’ stimuli required shorter SOA's to suppress contracting stimuli than the reverse configuration. Adding sounds further reduced SOA thresholds for both configurations (even for non-matched stimuli). CONCLUSIONS: In BR, visual looming predominates over receding. Adding auditory looming further enhances this looming predominance. This suggests auditory input can help resolve visual ambiguity. In FS, auditory input influenced SOA thresholds. Unlike in BR, this effect was not specific to matched audiovisual signals. FS appears more susceptible to auditory modulation generally- evidence that FS is distinct from BR and not just a ‘one-cycle’ version of BR.