Neuropsychologia 45 (2007) 1878–1888 Direct evidence for differential roles of temporal and frontal components of auditory change detection Shani Shalgi a , Leon Y. Deouell b,c,∗ a Department of Cognitive Science, The Hebrew University of Jerusalem, Jerusalem, Israel b Department of Psychology, The Hebrew University of Jerusalem, Jerusalem, Israel c Interdisciplinary Center for Neural Computation, The Hebrew University of Jerusalem, Jerusalem, Israel Received 21 July 2006; received in revised form 29 November 2006; accepted 29 November 2006 Available online 18 January 2007 Abstract Automatic change detection is a fundamental capacity of the human brain. In audition, this capacity is indexed by the mismatch negativity (MMN) event-related potential, which is putatively supported by a network consisting of superior temporal and frontal nodes. The aim of this study was to elucidate the roles of these nodes within the neural network of change detection. We used a dichotic paradigm in which subjects (N = 14) attended targets defined by either pitch or spatial location in one auditory stream while the MMN was measured in response to unattended deviants of pitch and spatial location in the other stream. The frontal and temporal components of the MMN were examined using current source density (CSD) measurements. Competition for processing resources nearly eliminated the temporal CSD mismatch response, in a highly feature-specific manner: the response to spatial location deviants was reduced when the target dimension was spatial location but not when it was pitch, whereas the reverse occurred for pitch deviants. In contrast, the frontal CSD mismatch response was neither affected by competition nor by general attention demands. Thus, within the network of change detection, the temporal generators are specifically associated with processing feature-specific information, whereas the role of the frontal generators remains unclear. Moreover, the results are inconsistent with a serial model in which the frontal generator is contingent on activation of the temporal generator. © 2006 Elsevier Ltd. All rights reserved. Keywords: Mismatch negativity; Current source densities; Biased competition; Pre-attentive; Sound localization Automatic detection of changes in the environment, which occur outside the focus of attention, is crucial for flexible behav- ior and survival. Understanding the neural underpinning of this function is a challenge for cognitive neuroscience. A window into this process is provided by the mismatch negativity (MMN; N¨ a¨ at¨ anen, Gaillard, & Mantysalo, 1978) event-related poten- tial, which is widely considered a physiological index of change detection (N¨ a¨ at¨ anen, Jacobsen, & Winkler, 2005; Schroger, 2005). Soon after the discovery of the MMN, N¨ a¨ at¨ anen and Michie (1979) suggested a model in which the neural activity underlying the MMN could be attributed to two sets of neural generators—a superior temporal generator, and a frontal gener- ator. They further suggested a functional dissociation between ∗ Corresponding author at: Department of Psychology, The Hebrew University of Jerusalem, Jerusalem 91905, Israel. Tel.: +972 506876075; fax: +972 25825659. E-mail address: Leon.Deouell@huji.ac.il (L.Y. Deouell). the two generators: the temporal generator was associated with establishment of memory traces and comparison with incoming stimulus attributes, whereas the frontal generator was related to involuntary triggering of attention invoked by the detected change. Substantial support for the dual generator model was provided by Giard and her colleagues (Deouell, Bentin, & Giard, 1998; Giard, Perrin, Pernier, & Bouchet, 1990), using current source density (CSD; Perrin, Pernier, Bertrand, & Echallier, 1989) mapping. These studies suggested a temporal generator which is predominantly activated in the hemisphere contralateral to the ear of stimulation, and a frontal generator involving mainly the right hemisphere. However, although Giard et al. (1990) adopted the idea of the functional division of labor between the two generators, they cautiously noted that “... nothing in our experimental paradigm allows us to attribute a definite func- tional role to each of these evoked potentials” (p. 638). Direct evidence for the suggested division of labor between the supe- rior temporal and frontal cortices is still lacking. Nevertheless, this model, to which we will refer below as the ‘canonical 0028-3932/$ – see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.neuropsychologia.2006.11.023