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 inherent 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 methodology. We removed the contribution of the source of the periodic structure, the glottal excitation produced by the vocal folds, from vowel stimuli and found that electromagnetic responses generated in the auditory cortex reflect this removal. The N1(m) amplitude decreased even though the rest of the acoustical features of the stimuli were identical. Thus, we conclude that speech production mechanisms have significant effects on human brain dynamics as reflected by magnetoencephalography and electroencephalograph. (C) 2001 Published by Elsevier Science Ireland Ltd.