N 1 and the mismatch negativity are spatiotemporally distinct ERP components : Disruption of immediate memory by auditory distraction can be related to N 1 TOM

Event-related potentials (ERPs) were recorded for ignored tones presented during the retention interval of a delayed serial recall task. Themismatch negativity (MMN) andN1ERP components weremeasured to discern spatiotemporal and functional properties of their generation. A nine-token sequence with nine different tone pitches was more disruptive than an oddball (two-token) sequence, yet this oddball sequence was no more disruptive than a single repeating tone (one-token). Tones of the nine-token sequence elicited augmented N1 amplitudes compared to identical tones delivered in the one-token sequence, yet deviants elicited an additional component (MMN) with distinct temporal properties and topography. These results suggested that MMN and N1 are separate, functionally distinct components. Implications are discussed for the N1 hypothesis and the changing-state hypothesis of the disruption of serial recall performance by auditory distraction. Descriptors: Auditory mismatch-negativity MMN, Auditory N1, Irrelevant sound effect, Serial recall, Auditory distraction, Selective attention The mismatch negativity (MMN; Näätänen, Gaillard, & Mäntysalo, 1978) is a frontocentrally distributed, relatively long-lasting component of the auditory event-related potential (ERP) that occurs in response to ‘‘deviant’’ sounds that violate some acoustic regularity. The auditory oddball sequence is the simplest paradigm in which MMN is investigated. In this paradigm, low-probability deviant sounds are interspersed among a repeating sequence of a highly probable ‘‘standard’’ sound, from which the deviant sounds differs in one ormore acoustic features. Violation of some regularity in the preceding auditory stimulation, as occurs within an oddball sequence, is necessary for the elicitation of MMN (Näätänen & Winkler, 1999). In contrast, the auditoryN1 waveFa frontocentrally negative ERP response occurring approximately 100 ms after stimulus onset (Näätänen & Picton, 1987)Fis elicited by the onset of any abruptly commencing sound. The N1 amplitude is augmented by sound change evenwhen acoustic change does not violate any preceding regularity. For example, relative to a sequence containing one repeated sound, ERPs exhibit an N1 amplitude enhancement when recorded from sequences in which each sound differs from the preceding sound (Campbell, Winkler, & Kujala, 2005; Campbell, Winkler, Kujala, & Näätänen, 2003; Jacobsen, Schröger, Horenkamp, & Winkler, 2003). The auditory N1 and MMN usually overlap in time. The current investigation aimed at testing whether N1 and MMN exhibit distinct spatiotemporal and functional characteristics. This issue has become controversial once more, since a recently proposed explanation of MMN has cast this component as a temporally modulated N1 response that is subject to an adaptation process characterized by differential attenuation of two N1 subcomponents upon repeated stimulation (Jääskeläinen et al., 2004). Thus, the detection of auditory regularities would not be a necessary prerequisite for recording anMMN-like wave; rather an acoustic change would be sufficient for its elicitation. The adaptation process assumed by Jääskeläinen et al. only requires that a given neuronal element has been recently stimulated, such that this element has become less responsive upon subsequent stimulation (cf. ‘‘refractoriness’’; Alcaini, Giard, Thévenet, & Pernier, 1994; Barry, Cocker, Anderson, Gordon, & Rennie, 1992; Butler, 1968; Woods & Elmasian, 1986). Accordingly, rare ‘‘deviant’’ stimuli in an oddball sequence activate fresh afferent neuronal elements and thus result in an augmented This work was, in part, supported by aMarie Curie Fellowship of the European Community programme ‘‘Improving the Human Research Potential and the Socio-Economic Knowledge Base’’ under contract number HPMF-CT-2000-00902, the University of Helsinki, the Academy of Finland (200522), and by theHungarianNational Research Fund (OTKA T048383). Address reprint requests to: Tom Campbell, Helsinki Collegium for Advanced Studies, P.O. Box 4, FIN-00014 University of Helsinki, Finland. E-mail: tom. [email protected] Psychophysiology, 44 (2007), 530–540. Blackwell Publishing Inc. Printed in the USA. Copyright r 2007 Society for Psychophysiological Research DOI: 10.1111/j.1469-8986.2007.00529.x