Middle Ear Muscle Contractions in Response to Non-Acoustic Stimuli: The Role of Voluntary Motor Activity
Abstract
Middle ear muscle contractions (MEMCs) are most commonly considered a response to high-level acoustic stimuli. However, MEMCs have also been observed in the absence of sound, either as a response to somatosensory stimulation or in concert with other motor activity. The relationship between MEMCs and non-acoustic sources is not well understood. This study examined the occurrence rate of MEMCs associated with different levels of voluntary eye closure effort while controlling for demographic and clinical factors in a large group of participants (N=190) with the presence of acoustic reflexes and excellent hearing sensitivity. MEMCs were detected via changes in total energy reflected in the ear using a filtered (0.2 to 8 kHz) click train. Participants were instructed to voluntarily close the eye ipsilateral to the MEMC detection probe at three levels of effort. Muscle activity associated with eye closure was measured using surface electromyography. Results revealed that MEMCs commonly occur in association with voluntary eye closure and that the likelihood of observation increases with eye closure effort level and associated orbicularis oculi muscle activity. MEMC occurrence rates for eye closure were higher than for high level brief acoustic stimuli in the same participant pool, suggesting that motor activity may be a more robust elicitor of MEMCs than acoustic stimuli. Thus, motor activity can serve as a confounding factor for auditory exposure studies. Finally, these results complicate the interpretation of impulsive noise damage risk criteria that assume MEMCs serve a consistent, uniform protective function.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 17, 2020
- Accession Number
- AD1109757
Entities
People
- Gregory A. Flamme
- Heath G. Jones
- Kristy K. Geiters
- Madeline V. Smith
- Nathaniel T. Greene
- Stephen M. Tasko
- William A. Ahroon
- William J. Murphy
Organizations
- United States Army Aeromedical Research Lab