Figure 1.

(a) Video image of an OHC in the whole-cell patch configuration. The contact between the cell and the patch electrode is at the cell’s synaptic pole. A driven glass fiber is brought against the cell’s ciliated pole, and its motion is measured by using the photodiode. (b) The set up is similar to that shown in a, but the recording is made from one cell that is a part of a cluster of cells. (c) Equivalent mechanical circuit representation of the cell and the driven fiber. The aggregate of the putative molecular motors that produce cell contraction and elongation in response to a voltage command (V) is modeled by the displacement source G(V). The displacement G(V) represents the unloaded (“open circuit”) motile response of the cell. The displacement produced by the piezoelectric bimorph on the distal end of the fiber is signified by the displacement source x_o. The total driving–point stiffness of the cell, measured at its ciliated pole, is K, and the stiffness of the fiber is k_o. Both stiffnesses are represented as springs. The displacement measured by the photodiode is x.