The Laryngeal Auditory Startle Reflex (LASR): A New Component of the Auditory Startle Response

The human startle response is a generalized flexion response elicited by an unexpected stimulus, whether auditory, somatosensory, vestibular, or visual in nature. This is the first report of a laryngeal component to the human auditory startle response, termed the laryngeal auditory startle reflex (LASR).

Case series of seven subjects (five females, two males; mean age 41 ± 12 years). Intralaryngeal hook wire electrodes were inserted specifically into the lateral cricoarytenoid (LCA) muscles to collect electromyographic (EMG) data. Surface EMG data were collected from masseter, mentalis, orbicularis oculi, sternomastoid, strap musculature, and abductor pollicis brevis. A sudden, loud auditory stimulus was time-locked with EMG recording equipment.

Activation of LCA muscles in response to the auditory stimulus was obtained in all subjects. Mean laryngeal response latency was 56 ms versus 61 ms for the sternocleidomastoid. Amplitude and duration varied across all muscles. All subjects displayed LASR habituation over time. Distraction techniques enhanced the startle reflex in all groups. One subject exhibited distinct early and late laryngeal components, with the late component occurring at 97 ms.

The human larynx exhibits an adductor startle reflex response to auditory stimuli, which is modulated by central pathways. This laryngeal behavior may serve various purposes depending on developmental age and may contribute to diseases involving inappropriate and prolonged laryngeal adduction.

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