Early electrophysiological indicators for predictive processing in audition: a review.

The auditory system essentially deals with sequential type of input and thus requires processing that is particularly suited to extract stimulus relations within a sequence. Evidence from a variety of paradigms converges to show that the auditory system automatically uses stimulus predictability for facilitating its sequential processing. This type of predictive processing does not require attentional processing of the sounds or cognitive control of the predictions, nor does it involve the preparation of motor responses to the auditory stimuli. We will present a taxonomy of paradigms and resulting electrophysiological indicators for such automatic predictive processing in terms of event-related potential components and oscillatory activity. These indicators will include signals of fulfilled predictions (match signals such as N1 attenuation, repetition positivity, and early evoked gamma band response enhancement) as well as signals of violated predictions (mismatch signals such as the mismatch negativity and stimulus omission responses). We will show how recent approaches have revealed particularly early indicators of predictive processing down to the level of the auditory middle-latency responses. We will discuss the strength of the various indicators in terms of a truly predictive account of auditory processing (as opposed to, e.g., a retrospective verification of predictions). Finally, we will discuss the benefits of a predictive system within and beyond auditory processing. In conclusion, we argue in favor of the overwhelming evidence for predictions in audition, flexibly instantiated on different levels and timescales, and we aim to provide guidance along a variety of research paradigms illustrating the existence of these predictions.