Does the cochlea compromise on sensitivity and frequency selectivity?

A tenet of cochlear physiology is that sharp tuning and sensitivity are directly interrelated. Here we show a reciprocal interdependence between tuning and sensitivity in the mammalian cochlea from measurements of basilar membrane (BM) mechanical tuning and neural suppression tuning curves of wild-type (Tectb^+/+) and β-tectorin mutant (Tectb^-/-) mice. The tectorial membrane (TM) of the mutants lacks striated-sheet matrix, which is likely to decrease longitudinal elastic coupling. Mechanical and neural tuning curves recorded in mutants are slightly less sensitive, although more sharply tuned. The inverse relationship between sensitivity and tuning observed in the mutants could be attributed to smaller numbers of the outer hair cells responding in synchrony due to reduced longitudinal coupling in the TM. We suggest that frequency tuning and high sensitivity are not necessarily concomitant but reciprocal properties of the cochlea.