What is the role of the efferent olivocochlear system in hearing?

• A. It projects to the auditory cortex to modulate perception directly.
• B. It regulates outer hair cell gain to adjust sensitivity and protect from damage.
• C. It inhibits inner hair cell transduction completely to reduce noise.
• D. It modulates outer hair cell gain to adjust sensitivity and protect from damage.

Answer: (D)

The efferent olivocochlear system provides a feedback control that tunes cochlear amplification by modulating outer hair cell activity. Medial efferent fibers release signals onto outer hair cells, reducing their electromotility and, as a result, lowering the gain of the cochlear amplifier. This dampens basilar membrane motion, decreases auditory nerve responses, and helps protect the ear from loud sounds while also aiding in detecting signals in noise. It does not send direct projections to the cortex to shape perception, and its main action is on outer hair cells rather than completely suppressing inner hair cell transduction.