Big and Powerful:. a Model of the Contribution of Bundle Motility to Mechanical Amplification in Hair Cells of the Bird Basilar Papilla

Stimulus amplification by hair cells contributes to sensitivity and frequency selectivity in all vertebrate hearing organs. Motility of the hair-cell bundle is likely to be an important contributor to this amplification; in non-mammalian hair cells, bundle motility is thought to be the sole amplification mechanism. The largest hair-cell bundles - in terms of stereovillar numbers - are found in the avian basilar papilla (cochlea). We examined these morphological data to evaluate the energy produced by the hair bundle, specifically by comparing this energy with the viscous loss in the subtectorial space. Hair-bundle forces are predicted to be effective into the kHz range and are thus a realistic candidate mechanism for the cochlear amplifier in birds. In contrast to the smaller bundles of mammalian hair cells, the effect of bundle motility should be considerably larger in birds.