Presentation
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Rate synchronization reveals a corresponding syllable rhythm in brain oscillations and speech productions
Poster C26 in Poster Session C, Friday, October 7, 10:15 am - 12:00 pm EDT, Millennium Hall
Deling He1, Eugene H Buder1, Gavin M Bidelman1,2; 1University of Memphis, 2Indiana University
Considerable research has highlighted that oscillatory brain activity contributes to speech processing via tracking quasi-periodic speech rhythms. Because the central syllable rhythm of the acoustic envelope is remarkably similar across languages (~4-5 Hz), we assumed that this intrinsic periodicity would reveal an organizing principle in both auditory and motor systems involved in speech. To assess relations between entrainment in the perceptual and production domains, we measured phase locking values for ongoing EEG signals to speech stimuli and simultaneous speech production synchronization to heard syllable rates between 2.5-8.5 Hz, values approximating to the ecological range of syllable rates across languages. Given that the origin of the intrinsic rhythm remains unclear, we also examined how accurately the rates were produced without concurrent auditory inputs, thereby isolating a more putative motor speech function. Our data from young adults revealed that neural synchronization flexibly adapts to the heard stimuli in a rate-dependent manner but that phase locking is boosted near ~4.5 Hz, the purported value of intrinsic rhythm. Audio-motor synchronization, which invokes simultaneous sensorimotor interaction, appeared to be optimal between 2.5-4.5 Hz. Linking auditory and motor systems, we found strong correlations between EEG and production synchronization abilities, which imply that individuals with stronger auditory-perceptual entrainment better match speech rhythms motorically. We further observed critical evidence that participants most precisely generated rates at 4.5 and 5.5 Hz in “pure” motor productions. Together, our findings support an intimate link between syllable rhythmic processing around 4-5 Hz in both the auditory and motor systems. The simultaneous speech synchronization demonstrated a low frequency constraint emerging on account of the direct sensorimotor integration. Our data are suggestive of an intrinsic syllable rhythm near 4-5 Hz that probably results from dynamics of the speech motor system coupled with experience-dependent tuning of the auditory perceptual system via the interface of perception-action.
Topic Areas: Perception: Auditory, Language Production