Inferred response polarities of cochlear hair cells

Abstract

Single-fiber responses were recorded from the auditory nerves of kanamycin-treated gerbils whose cochleas were subsequently processed for histological examination. On the basis of their abnormal responses to inferred trapezoidal displacements of the basilar membrane, the contacted fibers were classified according to that direction of basilar-membrane deflection that was associated with their excitation. A frequency–distance map was constructed for the gerbil’s cochlea with the help of cochlear-microphonic recordings and was used to infer the location of the hair cells innervated by the contacted fibers. Our correlations indicate that fibers innervating cochlear regions substantially depleted of outer hair cells were abnormal and were scala-vestibuli excitatory. Furthermore, fibers innervating cochlear regions containing full or nearly full complements of both inner and outer hair cells were either abnormal and scala-tympani excitatory, or were normal. These response polarities are consistent with the previously proposed polarity-opposition model of interaction between inner and outer hair cells in the cochlea. Subject Classification: [43]65.28, [43]65.35, [43]65.40, [43]65.42, [43]65.59.