Function of the laryngeal mechanoreceptors during vocalization

Area of Science:

• Neuroscience
• Physiology

Background:

• The superior laryngeal nerve (SLN) plays a critical role in laryngeal function, including sensation and motor control.
• Mechanoreceptors within the larynx are essential for coordinating breathing and vocalization.
• Previous classification of SLN mechanoreceptors relied primarily on respiratory-driven stimuli.

Purpose of the Study:

• To compare the activity of SLN mechanoreceptors using a respiration-based protocol versus a vocalization-based protocol in adult cats.
• To determine if a respiration-only classification adequately captures the functional roles of laryngeal mechanoreceptors.

Main Methods:

• Single fiber action potentials from the internal branch of the SLN were recorded in decerebrated cats.
• Mechanoreceptors were initially classified using a respiration-based protocol (pressure, flow, drive receptors).
• The same fibers were subsequently classified using a vocalization-based protocol (peak prephonatory, frequency-following, frequency-nonfollowing, inspiratory-modulated, or mixed) evoked by electrical midbrain stimulation.

Main Results:

• Data from five single fibers in three cats were analyzed.
• Two flow receptors showed peak activity post-vocalization during inspiration.
• A drive receptor was active during all airway maneuvers and phonation.
• Two receptors, frequency-following and frequency-nonfollowing, were exclusively active during phonation.

Conclusions:

• A respiration-based classification alone is insufficient for fully characterizing SLN mechanoreceptors.
• Vocalization is a significant stimulus that activates specific laryngeal mechanoreceptors.
• Frequency-following and frequency-nonfollowing receptors, active only during phonation, would be missed without vocalization stimuli.