The periodic structure of vowel sounds is reflected in human electromagnetic brain responses

Periodicity, which is caused by the vibration of the vocal folds, is an inh erent feature of vowel sounds. Whether this periodic structure is reflected in cerebral processing of vowels was addressed via the use of non-invasive brain research methods combined with advanced stimulus production methodol ogy. We removed the contribution of the source of the periodic structure, t he glottal excitation produced by the vocal folds, from vowel stimuli and f ound that electromagnetic responses generated in the auditory cortex reflec t this removal. The N1(m) amplitude decreased even though the rest of the a coustical features of the stimuli were identical. Thus, we conclude that sp eech production mechanisms have significant effects on human brain dynamics as reflected by magnetoencephalography and electroencephalograph. (C) 2001 Published by Elsevier Science Ireland Ltd.