Human middle-ear muscles rarely contract in anticipation of acoustic impulses: Implications for hearing risk assessments
| Autor: | Nathaniel T. Greene, William A. Ahroon, Heath G. Jones |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Adult
Male 0301 basic medicine medicine.medical_specialty Tympanic Membrane Movement media_common.quotation_subject Population Audiology Young Adult 03 medical and health sciences 0302 clinical medicine Hearing Predictive Value of Tests Conditioning Psychological Laser-Doppler Flowmetry medicine Humans Acoustic reflex education media_common education.field_of_study business.industry Hearing Tests Reproducibility of Results Classical conditioning Stapedius Middle Aged Anticipation Psychological Anticipation Reflex Acoustic Sensory Systems 030104 developmental biology medicine.anatomical_structure Acoustic Stimulation Impulse (psychology) Middle ear Conditioning Female Tensor Tympani business Risk assessment 030217 neurology & neurosurgery Muscle Contraction |
| Zdroj: | Hearing Research. 378:53-62 |
| ISSN: | 0378-5955 |
| DOI: | 10.1016/j.heares.2018.11.006 |
| Popis: | The current study addressed the existence of an anticipatory middle-ear muscle contraction (MEMC) as a protective mechanism found in recent damage-risk criteria for impulse noise exposure. Specifically, the experiments reported here tested instances when an exposed individual was aware of and could anticipate the arrival of an acoustic impulse. In order to detect MEMCs in human subjects, a laser-Doppler vibrometer (LDV) was used to measure tympanic membrane (TM) motion in response to a probe tone. Here we directly measured the time course and relative magnitude changes of TM velocity in response to an acoustic reflex-eliciting (i.e. MEMC eliciting) impulse in 59 subjects with clinically assessable MEMCs. After verifying the presence of the MEMC, we used a classical conditioning paradigm pairing reflex-eliciting acoustic impulses (unconditioned stimulus, UCS) with various preceding stimuli (conditioned stimulus, CS). Changes in the time-course of the MEMC following conditioning were considered evidence of MEMC conditioning, and any indication of an MEMC prior to the onset of the acoustic elicitor was considered an anticipatory response. Nine subjects did not produce a MEMC measurable via LDV. For those subjects with an observable MEMC (n = 50), 48 subjects (96%) did not show evidence of an anticipatory response after conditioning, whereas only 2 subjects (4%) did. These findings reveal that MEMCs are not readily conditioned in most individuals, suggesting that anticipatory MEMCs are not prevalent within the general population. The prevalence of anticipatory MEMCs does not appear to be sufficient to justify inclusion as a protective mechanism in auditory injury risk assessments. |
| Databáze: | OpenAIRE |
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