Browsing by Author "Saarinen, Timo"

Periodicity is an intrinsic feature of behavior that can be observed also in human speech production. Periodic movements prefer certain spontaneously occurring rates that often settle at the 2 Hz frequency in human motor behavior. These rates can be viewed to reflect optimal movement timing. Yet, the special role of spontaneous rates is undercharacterized in neural motor control, particularly for articulatory control of speech. This MEG-EMG study examined how the spontaneous speech rate manifests in electrophysiological interaction between the cortex and the mouth muscle. This interaction was measured with corticomuscular coherence in which elevation reflects more efficiently coupled periodic signaling between the structures. Coherence was quantified at different articulatory rates (0.8–5 Hz) in a syllable repetition experiment. The electrical muscle signals showed 2–3 Hz periodicity in both spontaneous syllable repetition and natural speech. In the syllable repetition experiment, corticomuscular coherence was centered bilaterally at the primary sensorimotor mouth cortex. Maximal coherence aligned with the 2–3 Hz production frequencies and it correlated with the spontaneous articulatory rate. Thus, the spontaneous speech periodicity had a neural correlate in the electrophysiological cortex-muscle interaction. Periodicity has been thought as a key principle in the organization of speech and this study highlights the significance of 2–3 Hz temporal frame in neural control of speech.