Auditory and tactile signals combine to influence vision during binocular rivalry

Resolution of perceptual ambiguity is a major function of cross-modal interactions, making the study of bistable perception in multisensory contexts a powerful and revealing tool. We previously used binocular rivalry, a visual bistable phenomenon, to show that touch can specifically interact with vision to resolve spatial conflict between the eyes (Lunghi & Alais, 2013). Here we investigate whether auditory and tactile stimuli can influence binocular rivalry generated by temporal conflict. Using visual stimuli of different temporal frequencies (filtered dynamic noise, 3.75 vs 15 Hz) to produce visual perceptual alternations, we added an amplitude modulated sound or vibration congruent with one of the rivaling temporal frequencies. Auditory and tactile stimulation interacted with binocular rivalry by promoting dominance of the congruent visual stimulus. This effect depended on auditory/tactile stimulus strength and was absent when modulation depth declined to 33%. However, in a trimodal experiment, combining auditory and tactile stimuli that were too weak to bias rivalry on their own produced a very strong influence over vision, suggesting summation of auditory and tactile temporal signals. Similarly, interleaving discrete pulses of auditory and tactile stimuli at half-frequency promoted dominance of the visual stimulus congruent with the combined supramodal frequency. Finally, audio-tactile stimuli combined at maximum strength but in anti-phase had no influence over visual rivalry, a cancellation effect again suggesting summation of audio-tactile modulations. These results demonstrate: (i) auditory and tactile processing at low temporal frequencies is functionally linked and may share a common neural substrate; (ii) visual activity can be synchronized by a congruent cross-modal signal in a frequency-selective way, suggesting a supramodal temporal binding mechanism.