Effects of Temporal Expectancy on Motor Control and Cognitive Processes Supporting Speech Production.

Background/Objectives: This study investigated the effects of temporal predictability on electrocortical processes underlying speech motor control and cognition. Methods: Twenty-one adults completed an S1-S2 (prompt for speech) visually cued delayed speech production task. The task required saying noun phrases or switching to saying the noun at 1.5 s vs. 3 s inter-stimulus intervals (ISI). Event-related potential indexing attentional effort (Contingent Negative Variation, CNV), speech motor planning (Bereitschaftspotential), speech programming (Late Readiness Potential, LRP), and speech onset latencies were compared between the categories using mixed effects analysis. Results: At 400-600 ms before S2 cue onset and speech motor planning, the 1.5 s ISI condition showed significantly higher mean amplitude of CNV at bilateral anterior frontal, central, and parietal electrode sites. At 400-600 ms, the Bereitschaftspotential representing movement planning showed a larger mean amplitude in the 1.5 s ISI condition at anterior frontal and central electrode sites that was moderated by CNV as covariate. Significant differences were evident between the speak and response switch conditions in LRP and speech onset. Conclusions: ISI-based effects of temporal predictability on speech motor planning, speech onset, and the cognitive processes supporting speech production are discussed.