Neuronal Adaptation and Formant Transition Direction in Vowels: An MMN Study

Abstract

Examined was whether the mismatch negativity (MMN) varied predictably in response to changes in the direction of frequency-modulated tone glides and equivalent second formant transitions in vowels (e.g., /ɪ/ as in “bit” and /e/ as in “bate”). A novel stimulus presentation paradigm was designed to distinguish the MMN from the N1 component. 10 normal-hearing adults with no neurological diseases were recruited and presented stimuli via insert earphones while they watched a silent, subtitled movie. Event-related potentials (ERPs) were recorded from 128 scalp electrodes. The MMN was successfully distinguished from the N1, marking participants’ ability to discriminate vowel stimuli only. A significant early P2 component, which decreased in size with successive stimulus presentations, was also elicited for vowels only and is believed to reflect formant encoding. Discrepancies between vowel and tone results are discussed along with clinical implications and contributions to the fields of ERP and vowel research.