Research Report Two separate mechanisms underlie auditory change detection and involuntary control of attention Teemu Rinne a,b, ⁎ , Anna Särkkä c , Alexander Degerman a , Erich Schröger d , Kimmo Alho a a Department of Psychology, University of Helsinki, Finland b Human Cognitive Neurophysiology Laboratory, UC Davis and VANCHCS, Martinez, CA 95616, USA c Cognitive Brain Research Unit, Department of Psychology, University of Helsinki, Finland d Institute for Psychology, University of Leipzig, Germany ARTICLE INFO ABSTRACT Article history: Accepted 11 January 2006 Available online 20 February 2006 We used behavioral and event-related potential (ERP) measures to study the neural mechanisms of involuntary attention switching to changes in unattended sounds. Our subjects discriminated two equiprobable sounds differing in frequency (fundamental frequency 186 or 196 Hz) while task-irrelevant intensity decrements or increments (-3, -6, -9, +3, +6, or +9 dB, standard intensity 60 dB HL) infrequently occurred in the same sounds. In line with the results of previous studies, discrimination performance deteriorated with increasing magnitude of the task-irrelevant intensity change. However, these distraction effects were dissimilar for intensity increments and decrements: while there were no differences in reaction time (RT) between intensity decrements and increments, hit rates (HR) were lower for large intensity increments than for large decrements. ERPs to task- irrelevant intensity increments and decrements were also distinctly different: the response to intensity increments consisted of an N1 enhancement, mismatch negativity (MMN), and P3a, while the response to intensity decrements consisted only of MMN. These results are consistent with the assumption that two separate mechanisms (indexed by N1 and MMN) underlie auditory change detection. However, the finding that distinct distraction effects were obtained for both intensity decrements and increments but that the P3a is elicited only by the intensity increments seems to suggest that P3a may not be regarded as a general index of attentional shift but rather it is only generated in conditions in which an enhanced N1 is elicited, too. © 2006 Elsevier B.V. All rights reserved. Keywords: Auditory change detection Distraction Event-related potential N1 MMN P3a 1. Introduction Sudden changes in unattended sounds may distract perfor- mance of an ongoing task as attention is involuntarily captured away from the task to the previously disregarded sounds. Such stimulus-driven control of attentional resources is referred to as involuntary attention. Based on the results of previous studies recording event-related potentials (ERP) to infrequent changes in repetitive acoustic stimulation, it has been suggested that involuntary attention is triggered by two distinct auditory cortex change detection mechanisms that respond to different information about the preceding acoustic input (Escera et al., 1998; Näätänen, 1992; Picton et al., 2000). The first mechanism, reflected in the N1 component of the ERP, detects acoustic changes based on activation of new neural units when a sound is presented in silence (i.e., after a BRAIN RESEARCH 1077 (2006) 135 – 143 ⁎ Corresponding author. Department of Psychology, P.O. Box 9, FI-00014 University of Helsinki, Finland. E-mail address: teemu.rinne@helsinki.fi (T. Rinne). 0006-8993/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2006.01.043 available at www.sciencedirect.com www.elsevier.com/locate/brainres