Effects of Reflex Middle-Ear Muscle Contractions on Cochlear Responses to Bone-Conducted Sound

Abstract

The effects of contralaterally elicited middle-ear muscle (MEM) reflexes on cochlear microphonic responses to air- and bone-conducted tones were examined in decerebrate cats. Stapedius effects on bone conduction were almost identical in configuration and amplitude to those on air conduction at all frequencies. However, tensor tympani effects were more complex, the configuration of the bone-conduction effects varying with the location of the transducer on the skull and with frequency. The relative contributions of the two muscles to the effects of joint contractions varied markedly between animals. It is suggested that non-reflex MEM contractions associated with activity of the facial musculature might provide protection against masking of environmental sounds by the low-frequency bone-conducted sound generated by such activity

Key Words:

• Middle-ear muscles
• Stapedial-muscle reflex
• Tensor tympani reflex
• Bone conduction
• Air conduction
• Cochlear microphonic response
• Decerebrate cat