Cochlear Mechanics

  • The cochlea houses the sensory cells in the mammalian auditory system. An active process boosts vibrations in the cochlea arising from sound, which largely determine the signal sent to the brain, more than a thousandfold. Although absence of the active process results in profound hearing loss, there is no consensus as to its mechanism.

  • The active process in nonmammals likely arises from active hair-bundle motility. The outer hair cells of mammals possess a second form of motility, somatic motility, in which the cell body contracts (elongates) in response to membrane-potential depolarization (hyperpolarization) (see figure). Modelling reveals that somatic motility can increase the characteristic frequency and sensitivity of the cochlea by providing feedback to active hair bundles1. The effects of hair-bundle motility and somatic motility depend, however, on their environment in vivo2.

  • New experimental techniques have additionally revealed that the cochlea vibrates in a complex manner in response to sound. We use computational models to interpret these observations and to form hypotheses about how the cochlea works1,4.