Detecting integration of top-down information using the mismatch negativity

Preliminary evidence from phoneme restoration

Abstract

The current study utilizes mismatch negativity in the phenomenon of phoneme restoration to investigate the critical debate regarding the integration of top down (lexical) and bottom up (acoustic) processing in spoken word recognition. Phoneme restoration, which occurs when phonemes missing from a speech signal are restored by the brain and may appear to be heard, was examined in a multi-standard oddball paradigm. Participants heard stimuli while watching a quiet animated film. Stimuli were divided into word and non- word conditions, with noise added to some stimuli to make them ambiguous. The many-to-one ratio of standards to deviants for generation of mismatch negativity (MMN) was achieved only if the brain could recover the missing phoneme in the ambiguous, noise-spliced stimuli. Both word and nonword conditions were compared to verify that an elicited MMN among words was contingent on involvement of the lexicon in the grouping of standards, and not some more general cognitive grouping procedure. Results from seven participants show preliminary support for the predicted effect: i.e., mismatch negativity for words but not for nonwords. This effect is contingent on phoneme restoration, and thus is consistent with recent literature suggesting that MMN is sensitive to higher information structures such as the mental lexicon. Keywords: phoneme restoration, MMN, lexical access, top-down information