Effects of Suprasegmental Features on the Processing of Spoken Words in the Human Brain: Evidence from Mismatch Negativity (MMN)

The study reported in the present paper aimed to determine the effect of prosodic cues on automatic word processing in the brain by comparing the mismatch negativity (MMN) component of the event-related potentials (ERP) elicited by isolated words and pseudowords. More specifically, it attempted to explore the influence of changes in certain suprasegmental cues such as fundamental frequency and intensity on the perception of linguistic stress patterns by native speakers of American English. The material chosen was a pair of English words in which a change of function from noun to verb is commonly associated with a shift of stress from the first to the second syllable. Neurophysiological brain activity was recorded to series of frequent (standard) stimuli and three types of rare (deviant) stimuli differing from the standard in one of three different ways: frequency, intensity, or in both features, and the mismatch negativity (MMN) component of event-related potentials (ERP), a brain correlate of automatic preattentive auditory processing, was computed. The results of the experiment showed that in both word and pseudoword conditions, deviants elicited MMNs in a biphasic nature; one with a time course of 110-160 ms and another with a time course of 200-300 ms. These negative deflections could be interpreted to reflect the deviation of a sound from the transient auditory memory trace of the standard. However, it was unclear whether the MMNs were elicited by a change of word stress as a linguistic pattern and, ergo, lexical activation or just changes in acoustic features. Additionally, the results of the experiment showed intensity, fundamental frequency, and combination of them contributed differentially to the prosodic information and hence, differed in their MMN amplitudes. Statistical analysis showed that the combination of the two acoustic dimensions is the most effective cue for stress perception