Poster #: 110
Topic: Speech and language (incl. deficits)
Thursday, Sep 10, 2015
Temporal integration of speech sound probed with mismatch negativity
1Neuropsychiatry, Ohara General Hospital, Fukushima, Japan
2Neuropsychiatry, Fukushima Medical University, Fukushima, Japan
Deviant sounds occurring in a sequence of standard sounds, in the absence of attention, elicit an event-related potential known as mismatch negativity (MMN). Standard sounds are encoded in auditory sensory memory trace and processed as a single unit within 160 -170 ms, where each unitary event stored is closely related to the temporal window of integration (TWI). The TWI of pure tone sound has already been reported. There are no reported correlations, however, between speech sounds and a temporal unit. It is well known that pure tone sounds are predominantly recognized in the right hemisphere, while speech sounds are recognized in the left. The goal of this study was to examine whether speech sounds were processed as a temporal unit like pure tone sounds, and if there were differences between right and left ear stimuli. Twenty-five healthy Japanese males participated. Stimuli consisted of the vowel /a/ spoken by a Japanese female, and the stimuli sequences were randomized from short standard sounds and three types of long duration deviant sounds. The stimuli were presented to both ears, separately. All bilateral stimuli induced definite MMN with similar peak latencies. The MMN peak amplitudes were gradually enhanced from the short to long duration deviant at Fz. No significant difference of peak amplitude at between T5 and T6 was observed. There were no differences in MMN between the right and left ear stimuli at Fz ,T5 and T6. These findings also show that bilateral deviant speech sounds were processed equally as a temporal unit.