Speech is a complex process that requires the coordination of multiple structures of the phonatory system regulated by the central nervous system. Specifically, the larynx is the key point necessary for the vocal folds to come into contact to convert the air that comes out of our lungs into sound. Vocal emission involves the genesis of a precise and prolonged expiration that provides an adequate pressure/air flow component to generate a subglottic pressure compatible with vocalization. The starting point for voluntary vocal production is the laryngeal motor cortex (LMC), a common structure in mammals, although the specific location within the cortex differs in humans. LCM projects to the periaqueductal gray matter (PGM), which leads to pontomedullary structures to locate the generators of laryngeal-respiratory motor patterns, necessary for vocal emission. All these regions present a high expression of FOXP2 transcription factor, necessary for brain and lung development that is closely related to vocalization. These central structures have in common that not only convey cardiorespiratory responses to environmental stress but also support vocalization. At clinical level, recent studies show that central circuits responsible for vocalization present an overactivity in certain speech disorders such as spasmodic dysphonia due to laryngeal dystonia.
Part of the book: Autonomic Nervous System