What Garcia Got Right: Understanding Cortical Signaling of the Glottis

Abstract

Phonation is a wonder of physics and physiology. In reductionist terms, the mechanics of the glottis can be viewed as a valve system: the streaming airflow from the lungs is passed through a dynamic and complex structure which is constantly changing aperture and configuration. The resulting pressure waves from air passing through the glottis are ultimately shaped and refined by the vocal tract giving rise to our unique voices. The nuance of this is extraordinary: as we sing and speak the vocal fold configuration is constantly changing in length and degree of contact under pressure conditions which are not always predictable. Yet the folds remain remarkably diligent in their ability to maintain equilibrium throughout these rapid changes. Without such discipline of this mechanism, we wouldn’t be capable of getting stability in any sound. Large, distal muscles of respiration are not designed to regulate such nuance at the millisecond level. So it is left to the larynx and vocal folds to balance the source sound of the system.This installment of “Minding the Gap” will be about how the brain controls this valve element at the center of our instrument: the intricate behaviors of the glottis. Neuroscience has shown that voicing, pitch, and phrasing are all signaled independently through the two laryngeal motor cortices which are a hallmark of our vocal learning abilities. Understanding these elements can help singers and teachers design targeted pedagogical strategies.