In most models of the mammalian cochlea, either mathematical or conceptual, the sensitivity of the BM to low level acoustic stimulus is explained by the presence of outer hair cell (OHC) somatic motility. However, recent experimental evidence indicates that OHC hair bundle (HB) motility can operate with submillisecond time constants. In this paper, we implement a simple phenomenological mathematical model of HB motility, based on the ansatz that HB forcing adds mechanical energy to the system. Our preliminary predictions using models that combine HB and somatic OHC motility indicate that HB motility is not necessary for cochlear amplification while OHC somatic motility is necessary. However we show how HB motility could work in synergy with OHC somatic motility to improve the sensitivity of the cochlea. Experiments to test and elaborate our claims are discussed.
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