Processing of auditory deviants with changes in one versus two stimulus dimensions

Authors


  • This research was supported by the Max-Planck-Institute for Psychological Research. I thank Martin Eimer, Werner Schubö, Marie Hèlène Ciard, and two anonymous reviewers for helpful comments on earlier drafts of this paper and Anna Ruppl, Friederike Schlaghecken, Renate Tschakert, and Christian Wolff for their help in conducting the experiments.

Address reprint requests to: Erich Schröger, Institut für Psychologie, Universität München, Leopoldstr. 13, 80802 München, Germany.

Abstract

Auditory event-related potentials (ERPs) in response to 50-ms tones were recorded from the human scalp. A standard stimulus (p= .88) and three different deviants were randomly presented via earphones. There were two one-dimensional deviants (one frequency and one location deviant) and one two-dimensional deviant, with changes in both frequency and location. In one condition, subjects read a book and ignored the auditory stimuli, whereas in another condition they tried to discriminate deviants from standards. In the ignore condition, the two-dimensional deviant elicited an enhanced mismatch negativity (MMN) as compared with the MMNs elicited by the one-dimensional deviants. The temporal and the topographic distributions of the two-dimensional MMNs could be modeled by adding the one-dimensional MMNs. This additivity of the MMNs probably results from the independent activity of separate neural populations generating the frequency and the location MMN. In the attend condition, the deviance-related ERP effects were not additive in the N2b and P3 range, implicating that the neural processes involved in the conscious detection of changes in location and frequency were not independent.

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