Feedback control of the auditory periphery: Anti-masking effects of middle ear muscles vs. olivocochlear efferents

• Published in: Journal of communication disorders Vol. 31; no. 6; pp. 471 - 483
• Main Authors: Liberman, M.Charles, Guinan, John J.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY Elsevier Inc 01.11.1998; Elsevier Science
• Subjects: Animals; Cats; Cochlea - physiology; Ear, Middle - physiology; Feedback; Humans; Noise - adverse effects; Perceptual Masking; Reflex - physiology; Stapedius - physiology
• ISSN: 0021-9924; 1873-7994
• DOI: 10.1016/S0021-9924(98)00019-7

Both MEM and MOC systems are sound-evoked reflexes to the auditory periphery which can be elicited by sound in either ear. Both MEM and MOC systems can increase thresholds in the auditory periphery: the MEM system acts by stiffening the ossicular chain, the MOC system by decreasing outer hair cell amplification of sound-induced motion in the inner ear. MEM-induced attenuations are largest for low frequency stimuli, MOC-induced attenuations are largest for mid- to high-frequency sounds. Both MEM and MOC systems can have anti-masking effects. The MEM reflex can decrease the masking of high-frequency signals by low-frequency noise (i.e., the upward spread of masking). The MOC reflex is complementary in that it minimizes masking of high-frequency transient signals by high-frequency continuous noise. MEM anti-masking arises by reducing suppressive masking and can improve masked thresholds at high frequencies. MOC anti-masking arises by counteracting excitatory masking. It does not improve masked thresholds, but can improve the detectability of small suprathreshold intensity increments. Anti-masking effects of both MEM and MOC systems should be reduced in cases of sensorineural hearing loss.