| Popis: |
The Auditory Hazard Assessment Algorithm for Humans (AHAAH) is an electrical equivalence model of the human ear designed to predict the risk for auditory injury from a given impulse noise exposure. One concern with the model is that the middle-ear muscle contraction (MEMC) associated with the acoustic reflex is implemented as a protective mechanism for certain instances in which a person is “warned” prior to the impulse. The current study tested the assumption that the MEMC can be elicited by a conditioning stimulus prior to sound exposure (i.e., a “warned” response). In order to quantify the MEMC, we used laser-Doppler vibrometry to measure tympanic membrane motion in response to a reflex-eliciting acoustic impulse. After verifying the MEMC, we attempted to classically condition the response by pairing the reflex-eliciting acoustic impulse (unconditioned stimulus, UCS) with various preceding stimuli (conditioned stimulus, CS). Changes in the magnitude and/or time-course of the MEMC following repeated UCS-CS pairings would be evidence of MEMC conditioning. Out of the 55 subjects tested so far, both non-conditioned (n = 53) and conditioned (n = 2) responses have been observed. These findings suggest that a “warned” MEMC may not be present in enough people to justify inclusion for being considered protective. |
