Look now and hear what's coming: on the functional role of cross-modal phase reset.

In our multisensory environment our sensory systems are continuously receiving information that is often interrelated and must be integrated. Recent work in animals and humans has demonstrated that input to one sensory modality can reset the phase of ambient cortical oscillatory activity in another. The periodic fluctuations in neuronal excitability reflected in these oscillations can thereby be aligned to forthcoming anticipated sensory input. In the auditory domain, the example par excellence is speech, because of its inherently rhythmic structure. In contrast, fluctuations of oscillatory phase in the visual system are argued to reflect periodic sampling of the environment. Thus rhythmic structure is imposed on, rather than extracted from, the visual sensory input. Given this distinction, we suggest that cross-modal phase reset subserves separate functions in the auditory and visual systems. We propose a modality-dependent role for cross-modal input in temporal prediction whereby an auditory event signals the visual system to look now, but a visual event signals the auditory system that it needs to hear what is coming. This article is part of a Special Issue entitled <Human Auditory Neuroimaging>.