The mismatch-negativity (MMN) component of the auditory event-related potential to violations of abstract regularities: a review

The mismatch-negativity (MMN) component of the event-related potential (ERP) has been extensively used to study the preattentive processing and storage of regularities in basic physical stimulus features (e.g., frequency, intensity, spatial location). However, studies reviewed in the present article reveal that the auditory analysis reflected by MMN also includes the detection and use of more complex, "abstract", regularities based, for example, on relationships between various physical features of the stimuli or in patterns present in the auditory stream. When these regularities are violated, then MMN is elicited. Thus, the central auditory system performs even at the pre-attentive, auditory-cortex level surprisingly "cognitive" operations, such as generalization leading to simple concept formation, rule extraction and prediction of future stimuli. The information extracted often seems to be in an implicit form, not directly available to conscious processes and difficult to express verbally. It can nevertheless influence the behavior of the subject, for example, the regularity violations can temporarily impair performance in the primary task. Neural, behavioral and cognitive events associated with the development of the regularity representations are discussed.