Hydromechanical Structure of the Cochlea Supports the Backward Traveling Wave in the Cochlea In Vivo

Figure 3

Model of the cochlear passive hydromechanical structure. (a) Schematic of the model structure. The thick solid lines represent the fluid channel and the open rectangles represent the cochlear partition, or simply BM. In this lumped model, the fluid channel and the cochlear partition (or simply BM) were divided into a series of sections. The rectangle is wider and shorter at the base and thinner and longer at the apex, representing the BM stiffness gradient: stiffer at the base and softer at the apex. (b) Circuit analogy of each section. The fluid mass is analogous to a series of inductors; the fluid viscosity is analogous to a series of resistors; the stiffness of the partition is analogous to a capacitor. (c) At each section, the forward and backward waves experience the same low-pass filtering. (d) Schematic shows the low-pass filters that the traveling wave experiences during the forward and backward propagation. Note that the forward direction is towards the low frequency. The roll-off frequency at the basal, middle, and apical locations decreases.

(a)

(b)

(c)

(d)