ABSTRACT
Mismatch negativity (MMN) is an electrophysiological manifestation of pre-attentive processing in response to oddball stimuli (Kraus & Nää tä nen, 1995; Näätänen & Escera, 2000). Although MMN has been extensively studied through the use of auditory stimuli, there are some reports suggesting that it can be elicited in other modalities (e.g., Alho, Woods, Algazi, & Naatanen, 1992; Kekoni, Hämäläinen, McCloud, Reinikainen, & Näätänen, 1996; Krauel, Schott, Sojka, Pause, & Ferstl, 1999; Shinozaki, Yabe, Sutoh, Hiruma, & Kaneko, 1998; Tales, Newton, Troscianko, & Butler, 1999; Woods, Alho, & Algazi, 1992; for a review, see Näätänen & Alho, 1995; for animal studies see Astikainen, Ruusuvirta, & Korhonen, 2000). MMN is usually elicited using an oddball paradigm, whereby different types of occasional changes (in an otherwise recurrent stimulus sequence) are presented outside the focus of attention, and is regarded as an automatic change-detection response (Näätänen, Gaillard, & Mäntysalo, 1978). In a typical MMN odd-ball paradigm, a ‘'deviant” auditory stimulus is sporadically distributed within a sequence of “standard” auditory stimuli. The MMN is evident in the difference waveform obtained by subtracting the ERP elicited by the standard stimulus from that evoked by the deviant stimulus. The difference-waveform in adults is characterized by a negative-going component with a typical latency peaking between 100 and 250 ms from the onset of the deviant stimulus, and with an amplitude that depends on the magnitude of the deviance. MMN has been demonstrated by manipulating basic physical features of pure and harmonic tones, e.g., frequency, intensity, duration, inter-stimulus interval (ISI), and location (for a review, see Näätänen, 1992), as well as by more complex dimensions such as phonetic information, temporal order, or an abstract relation between pairs of tones (for a review, see Kraus & Cheour, 2000; Näätänen & Tiitinen, 1998; Näätänen & Winkler, 1999). Although other theoretical explanations exist (e.g., Winkler, Karmos, & Näätänen, 1996), MMN is generally viewed as an outcome of an alleged mechanism that compares current auditory input to memory traces formed by previous auditory inputs and signals at an incongruent occurrence (Cowan, Winkler, Teder, & Näätänen, 1993; Näätänen, 1990, 1992; Ritter, Deacon, Gomes, Javitt, & Vaughan, 1995).
