Cochlear Microcircuits

The mammalian cochlea functions as a sensitive frequency analyzer of the acoustic world. To a large extent, this operation is intrinsic to the peripheral organ itself, resulting from the exquisitely differentiated mechanics of the sensory epithelium that encodes sound onto cochlear afferents. The precise arrangement of afferent innervation further refines and differentiates that coding. In addition, cochlear operation is modulated by feedback from efferent neurons making contact with hair cells and afferent neurons. In this way, microcircuits of the auditory periphery involve an intricate interplay of micromechanics and cellular integration. This chapter will describe that interplay, with an emphasis on the synaptic connections of sensory hair cells with afferent and efferent neurons. To do so requires an understanding of the peripheral transduction pathway, which begins with an overview of cochlear function.