The physiology of the organ of Corti

The cochlea resolves low-level acoustic signals into their individual frequency components and converts these into the auditory neural code. Vibrations of the basilar membrane excite the hair cells through displacements of the stereocilia. These displacements directly control the opening of non-selective membrane channels so that when the stereocilia are displaced in the direction of their tallest row, receptor current is driven into the hair cells by the potential difference between the positive endocochlear potential and the negative hair cell membrane potential. The inner hair cells (IHCs) appear to have a primary sensory role: their dynamic range and frequency selectivity are similar to those of the numerous afferent fibres with which they form synapses. Outer hair cells (OHCs), on the other hand, while sharply tuned, receive few afferent fibres and a massive efferent innervation. There is strong evidence that OHCs play an active motile role in producing the exquisite sensitivity and frequency selectivity of the cochlea.