Auditory mechanisms detecting sound-stream and categorical violations: A MEG mismatch study

摘要

Based on an MEG mismatch field measurement using an ever-ascending scale and a vowel sequence, the auditory mechanisms forming a coherent sound stream and detecting stream violations were investigated. For ten listening subjects, a seven-tone sequence forming an ever-ascending scale was repeatedly presented in Experiment I, and a three-vowel sequence was repeatedly presented in Experiment II. Two stream violations were contrasted; one was stream violation in which a member sound is presented at out-of-stream positions, and the other was categorical violation in which a non-member sound is presented in a random position. Both types of violations elicited a mismatch-like magnetic field (MMF). The categorical violation elicited a larger MMF with a shorter peak latency than the stream violation in the vowel sequence. The estimated ECD localized in the auditory cortex differed between the two violation conditions. These results suggest that formation and maintenance of a sound-stream is carried out in the auditory cortex. The neural resources maintaining vowel sound stream at least partially differ from those maintaining musical streams, and those detecting a stream violation partially differ from those detecting a categorical violation.