The representation of audiovisual regularities in the human brain

Neural representation of auditory regularities can be probed using the MMN, a component of ERPs generated in the auditory cortex by any violation of that regularity. Although several studies have shown that visual information can influence or even trigger an MMN by altering an acoustic regularity, it is not known whether audiovisual regularities are encoded in the auditory representation supporting MMN generation. We compared the MMNs elicited by the auditory violation of (a) an auditory regularity (a succession of identical standard sounds), (b) an audiovisual regularity (a succession of identical audiovisual stimuli), and (c) an auditory regularity accompanied by variable visual stimuli. In all three conditions, the physical difference between the standard and the deviant sound was identical. We found that the MMN triggered by the same auditory deviance was larger for audiovisual regularities than for auditory-only regularities or for auditory regularities paired with variable visual stimuli, suggesting that the visual regularity influenced the representation of the auditory regularity. This result provides evidence for the encoding of audiovisual regularities in the human brain.