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This Article Full Text Full Text (PDF) All Versions of this Article: 585/3/779    most recent jphysiol.2007.143438v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Henriquez, V. M. Articles by Ludlow, C. L. Search for Related Content PubMed PubMed Citation Articles by Henriquez, V. M. Articles by Ludlow, C. L. Related Collections Neuroscience

¹ Laryngeal and Speech, Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA

The laryngeal adductor response (LAR) is a protective reflex that prevents aspiration and can be elicited either by electrical stimulation of afferents in the superior laryngeal nerve (SLN) or by deflection of mechanoreceptors in the laryngeal mucosa. We hypothesized that because this reflex is life-sustaining, laryngeal muscle responses to sensory stimuli would not be suppressed during volitional laryngeal tasks when compared to quiet respiration. Unilateral electrical superior laryngeal nerve stimulation was used to elicit early (R1) and late (R2) responses in the ipsilateral thyroarytenoid muscle in 10 healthy subjects. The baseline levels of muscle activity before stimulation, R1 and R2 response occurrence and the integrals of responses were measured during each task: quiet inspiration, prolonged vowels, humming, forced inhalation and effort closure. We tested whether R1 response integrals during tasks were equal to either: (1) baseline muscle activity during the task added to the response integral at rest; (2) the response integral at rest minus the baseline muscle activity during the task; or (3) the response integral at rest. R1 response occurrence was not altered by task from rest while fewer R2 responses occurred only during effort closure and humming compared to rest. Because the R1 response integrals did not change from rest, task increases in motor neuron firing did not alter the LAR. These findings demonstrate that laryngeal motor neuron responses to sensory inputs are not gated during volitional tasks confirming the robust life-sustaining protective mechanisms provided by this airway reflex.

(Received 18 August 2007; accepted after revision 16 October 2007; first published online 25 October 2007)
Corresponding author C. L. Ludlow: Laryngeal and Speech Section, National Institute of Neurological Disorders and Stroke, Bldg. 10 Room 5D 38, 10 Center Drive MSC 1416, Bethesda, MD 20892-1416, USA. Email: ludlowc{at}ninds.nih.gov