Supporting Evidence from Single Unit Experiments for the Cochlea as an Addressed Delay Line

WE have already outlined the principles of a theory of cochlear organization^{1, 2} whereby acoustic signal components in the low and mid frequency range—-that is to say, frequencies for which good or moderate phase locking of unit response is possible—are detected by the cochlea using an approximate cross-correlation mechanism which operates on the time varying signal displayed along the basilar membrane, the latter acting as an acoustic exponential delay line. The running correlations are performed using fixed patterns of control fibres addressed to the outer hair cells, the pattern of addressing for each control fibre group corresponding to an instantaneous wave pattern for a specific frequency defined by the location of the fibre system along the length of the membrane. The fibres of each control system synapse with the afferent dendrites associated with a definite inner hair cell and act as a frequency sensitive gate, the inner hair cell of the assembly providing generator current related to signal amplitude.