PRE-ATTENTIVE PROCESSING OF SPECTRALLY COMPLEX SOUNDS WITH ASYNCHRONOUS ONSETS - AN EVENT-RELATED POTENTIAL STUDY WITH HUMAN-SUBJECTS

Neuronal mechanisms involved in the processing of complex sounds with asynchronous onsets were studied in reading subjects. The sound onset asynchrony (SOA) between the leading partial and the remaining complex tone was varied between 0 and 360 ms. Infrequently occurring deviant sounds (in which one out of 10 harmonics was different in pitch relati ve to the frequently occurring standard sound) elicited the mismatch n egativity (MMN), a change-specific cortical event-related potential (E RP) component. This indicates that the pitch of standard stimuli had b een pre-attentively coded by sensory-memory traces. Moreover, when the complex-tone onset fell within temporal integration window initiated by the leading-partial onset, the deviants elicited the N2b component. This indexes that involuntary attention switch towards the sound chan ge occurred. In summary, the present results support the existence of pre-perceptual integration mechanism of 100-200 ms duration and emphas ize its importance in switching attention towards the stimulus change. (C) 1997 Elsevier Science Ireland Ltd.