Speech rhythm in the perception-action-cycle

Spoken language is a complex signal that evolves over time and conveys rhythm across multiple timescales. Beyond the signal level, there is rhythm in social aspects of speech communication such as joint-attention, gestures, or turn-taking. Neural oscillations have in many cases been shown to directly reflect the rhythmic features of speech. However, the knowledge about origins, specific functions, and potential interactions of different rhythms and their neural signatures is far from complete. An integrative perspective that builds on phylogenetic and ontogenetic developments can provide some of the missing components. Here we propose that speech production and perception engage evolutionary ancient temporal processing mechanisms that guide sensorimotor sequencing and the allocation of cognitive resources in time. Slow-wave (delta-to-theta band) oscillations are the designated common denominator of these mechanisms, which interact in a speech-specific variant of the perception-action-cycle with the goal to achieve optimal temporal coordination and predictive adaptation in speech communication.