COGNITIVE NEUROSCIENCE AND NEUROPSYCHOLOGY NEUROREPORT 0959-4965 & Lippincott Williams & Wilkins Vol 12 No 11 8 August 2001 2583 Cerebral mechanisms underlying orienting of attention towards auditory frequency changes Elena Yago, 1 Carles Escera, 1,CA Kimmo Alho, 1,2 and Marie-He Âle Áne Giard 3 1 Neurodynamics Laboratory, Department of Psychiatry and Clinical Psychobiology, University of Barcelona, P. Vall d'Hebron 171, 08035-Barcelona, Catalonia, Spain; 2 Cognitive Brain Research Unit, Department of Psychology, PO Box 13, FIN-00014 University of Helsinki, Finland; 3 Mental Process and Brain Activation, INSERM-U280, 151, cours Albert-Thomas, 69424 Lyon cedex 03, France CA Corresponding Author Received 23 May 2001; accepted 5 June 2001 Brain mechanisms underlying detection of auditory frequency changes were studied with event-related potentials (ERPs) in 14 human subjects discriminating visual stimuli. Scalp-current density mapping revealed bilateral components of mismatch negativity (MMN) in frontal and auditory cortices. Deviance- related activations in frontal and temporal cortex began to be signi®cant at 94 ms and 154 ms in the right hemisphere, and at 128 ms and 132 ms in the left hemisphere. The magnitude of MMN-neuroelectric currents from the left temporal cortex correlated signi®cantly (r 0.56, p , 0.05) with distraction caused by MMN-eliciting deviant tones. These results suggest a complex cerebral circuitry involved in frequency change detec- tion and strongly support the role of this circuitry in driving attention involuntarily towards potentially relevant frequency changes in the acoustic environment. NeuroReport 12:2583± 2587 & 2001 Lippincott Williams & Wilkins. Key words: Audition; Current density; Event-related brain potentials; Human; Mismatch negativity; Orienting response; Source analysis INTRODUCTION Detecting potentially relevant changes occurring in the unattended environment and the subsequent orienting of attention is a fundamental function for biological survival. In the auditory modality, a modality-speci®c change-detec- tor mechanism has been proposed to play a crucial role in driving attention involuntarily towards unattended acous- tic changes [1]. This mechanism is re¯ected in an event- related brain potential (ERP) called mismatch negativity [2] (MMN). MMN generation is based on a sensory memory system detecting acoustic irregularities by comparison of each new afferent stimulus with a neural trace of the preceding repetitive auditory stimulation [1]. The func- tional role of MMN generator processes in involuntary attention switching is strongly supported by recent studies showing deterioration of task performance, i.e. increased reaction time and decreased hit rate to target stimuli delivered after irrelevant MMN-eliciting, deviant sounds occurring in a task-irrelevant sound sequence [3±5]. Source localization of electrically and magnetically re- corded MMNs, as well as intracranial recordings in cats, monkeys, and humans have shown that MMN has bilat- eral generators in the primary auditory cortex or its vicinity (for a review, see [6]). In addition, scalp current density mapping of deviance-related negativities [7±9] has suggested a frontal contribution to MMN generation. A frontal contribution to MMN generation is also supported by studies showing attenuation of its amplitude in pa- tients with lesions in the dorsolateral prefrontal cortex [10,11]. According to the current theory [1], the supratem- poral MMN component is related to the analysis of the stimulus features and to the sensory memory trace pro- cesses involved in MMN generation [12,13], whereas the frontal MMN component is apparently a ®rm candidate to represent the neuroelectric signal triggering the attention switching response [1,7]. Recent evidence supports that frontal and temporal MMN generators may indeed have different functional roles [9,14]. These later authors found that increasing the standard stimulus probability enhanced the frontal MMN component, whereas the temporal MMN component remained unaffected. This result suggests that the frontal component of MMN may be involved in the processing of the unfamiliarity of deviant stimuli, and thus in the initiation of attention switching. These assump- tions on the functional roles of MMN subcomponents have been supported by a recent study of Rinne et al. [15] in which the temporal dynamics of the activations under- lying MMN generation were addressed. By using mini- mum-norm estimate analysis of deviance-related EEG and MEG responses, these authors found that the frontal MMN generators to duration deviant tones activated on average by 8 ms after the supratemporal auditory cortex ones. To further investigate the cerebral networks underlying