Auditory processing that leads to conscious perception: A unique window to central auditory processing opened by the mismatch negativity and related responses RISTO NA ¨ A ¨ TA ¨ NEN, a,b,c TEIJA KUJALA, c and ISTVA ´ N WINKLER, c,d,e a Department of Psychology, University of Tartu, Tartu, Estonia b Centre of Integrative Neuroscience (CFIN), University of Aarhus, Aarhus, Denmark c Cognitive Brain Research Unit, Institute of Behavioural Sciences, University of Helsinki, Helsinki, Finland d Department of Experimental Psychology, Institute for Psychology, Hungarian Academy of Sciences, Budapest, Hungary e Institute of Psychology, University of Szeged, Hungary Abstract In this review, we will present a model of brain events leading to conscious perception in audition. This represents an updated version of Na¨ a¨ ta¨ nen’s previous model of automatic and attentive central auditory processing. This revised model is mainly based on the mismatch negativity (MMN) and N1 indices of automatic processing, the processing negativity (PN) index of selective attention, and their magnetoencephalographic (MEG) and functional magnetic resonance imaging (fMRI) equivalents. Special attention is paid to determining the neural processes that might underlie conscious perception and the borderline between automatic and attention-dependent processes in audition. Descriptors: Central auditory processing, Event-related potential (ERP), Mismatch negativity (MMN), N1 One of the most exciting issues of modern cognitive neuroscience is the division to, and borderline between, brain processes that underly or do not underly conscious experience. For example, how much of auditory processing occurs outside of our attention and conscious experience and, further, what are the brain mech- anisms that determine whether conscious perception occurs or not? These questions will be the scope of the present review which will present a model of preconscious and conscious processes in audition that aims at determining the functional borderline be- tween the two processing modes. This model is an extension of Na¨ a¨ ta¨ nen’s (1990) model on attention and automaticity in au- ditory processing. The principal tool that has developed this model is the mismatch negativity (MMN) (Na¨a¨ ta¨ nen, Gaillard, & Ma¨ ntysalo, 1978). The (auditory) MMN is a fronto–centrally negative event-related potential (ERP) component that is elicited by sounds that violate the automatic predictions of the central auditory system. The MMN and its magnetoencephalographic (MEG) equivalent, the MMNm (Hari et al., 1984) provide a unique window to preconscious central auditory processing. Re- sults obtained for the N1 (Na¨a¨ ta¨ nen & Picton, 1987) and the processing negativity (PN) described by Na¨ a¨ ta¨nen et al. (1978) will also be used in specifying this model.Before introducing the model, it is necessary to examine the functional significance and separability of these overlapping brain responses, because these are central to the model. Moreover, this discussion will help in interpreting the roles that the processes that generate these re- sponses play in the model. The mismatch negativity (MMN). The MMN was initially isolated from the ‘‘N2’’ (Ford, Kopell, et al., 1976a, 1976b; Simson, Vaughan, & Ritter, 1976, 1977; Squires, Squires, & Hillyard, 1975; Squires, Wickens, Squires, & Donchin, 1976;) and the ‘‘N2-P3a’’ (Snyder & Hillyard, 1976) wave complexes, that are typically elicited in auditory oddball sequences, by Na¨ a¨ ta¨ nen et al. (1978; see also Na¨ a¨ ta¨ nen, 1975) through the use of deviant- standard difference waveforms. In contrast, the N1, an obli- gatory fronto–centrally negative-polarity response that peaks at about 100 ms from sound onset, manifests as a separate ERP peak. The MMN and its magnetic counterpart MMNm usually become clearly visible only through a subtraction procedure, in which the ERP response to some control stimulus, such as the frequent stimulus (‘‘standard’’), is subtracted from the response elicited by the infrequent stimulus ‘‘deviant.’’ For a review of the proper control for deriving the MMN, see Kujala, Tervaniemi, and Schro¨ ger (2007). Further, Na¨ a¨ ta¨ nen, Simpson, and Loveless (1982) showed that, after the MMN (‘‘N2a’’) is removed from the N2 wave complex by subtraction, the remaining waveform can be identified as the ‘‘N2b’’ response. The N2b response has a somewhat posterior topography compared to the N1 and also to This research was supported by The Philips Nordic Prize for 2007 for Achieved and Continued Research Work on Neurodevelopmental Dis- orders, the Academy of Finland (projects 1122745 and 1128840), and the European Commission (ICT-FP7-231168). Address correspondence to: Risto Na¨ a¨ ta¨ nen, Cognitive Brain Re- search Unit, Institute of Behavioural Sciences, P. O. Box 9 (Silt- avuorenpenger 1B), 00014 University of Helsinki, Finland. E-mail: risto.naatanen@helsinki.fi Psychophysiology, 48 (2011), 4–22. Wiley Periodicals, Inc. Printed in the USA. Copyright r 2010 Society for Psychophysiological Research DOI: 10.1111/j.1469-8986.2010.01114.x 4