Asynchrony from synchrony: long-range gamma-band neural synchrony accompanies perception of audiovisual speech asynchrony

Real-world speech perception relies on both auditory and visual information that fall within the tolerated range of temporal coherence. Subjects were presented with audiovisual recordings of speech that were offset by either 30 or 300 ms, leading to perceptually coherent or incoherent audiovisual speech, respectively. We provide electroencephalographic evidence of a phase-synchronous gamma-oscillatory network that is transiently activated by the perception of audiovisual speech asynchrony, showing both topological and time–course correspondence to networks reported in previous neuroimaging research. This finding addresses a major theoretical hurdle regarding the mechanism by which distributed networks serving a common function achieve transient functional integration. Moreover, this evidence illustrates an important dissociation between phase-synchronization and stimulus coherence, highlighting the functional nature of network-based synchronization.