Limit cycles for speech

TL;DR

This paper uncovers a fundamental rhythmic organization in speech articulatory movements by revealing limit cycle dynamics, bridging the gap between the rhythmicity observed in acoustic and neuronal activity and the traditionally discrete view of speech movements.

Contribution

It introduces a novel representation of speech movements that reveals underlying limit cycle organization, providing new insights into speech motor control.

Findings

Revealed limit cycle organization in speech articulatory movements

Uncovered rhythmic structure in speech motor activity

Reconciled biological rhythmicity with discrete speech actions

Abstract

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.