Limit cycles for speech
This resolves a long-standing problem in understanding the fundamental motor organization of speech, which is incremental in revealing rhythmicity at the individual action level.
The study tackled the tension between rhythmicity and discreteness in speech movements by demonstrating a pervasive limit cycle organization in articulatory actions, revealing previously inaccessible rhythmic structure.
Rhythmic fluctuations in acoustic energy and accompanying neuronal excitations in cortical oscillations are characteristic of human speech, yet whether a corresponding rhythmicity inheres in the articulatory movements that generate speech remains unclear. The received understanding of speech movements as discrete, goal-oriented actions struggles to make contact with the rhythmicity findings. In this work, we demonstrate that an unintuitive -- but no less principled than the conventional -- representation for discrete movements reveals a pervasive limit cycle organization and unlocks the recovery of previously inaccessible rhythmic structure underlying the motor activity of speech. These results help resolve a time-honored tension between the ubiquity of biological rhythmicity and discreteness in speech, the quintessential human higher function, by revealing a rhythmic organization at the most fundamental level of individual articulatory actions.