Experimental setup.

(A) Top-down view of a freestanding hair bundle with a glass probe (black line positioned vertically across the image) attached to the tallest row of stereocillia. Because of light piping, the stereocillia appear much brighter than the background. Scale bar: 2.5 m. (B) Schematic diagram showing a side view of a hair bundle with a probe attached. The piezoelectric actuator displaces the probe's base in the direction of the bundle's axis of sensitivity indicated by the arrow in the figure. (C) Top-down view of hair bundles coupled to the otolithic membrane. The pits in the membrane into which the bundles protrude give rise to the bright ellipses around each bundle. The shadow of the probe's tip has been highlighted with the dashed line. Scale bar: 5 m. (D) Schematic diagram of a side view of hair bundles coupled to the otolithic membrane and stimulated with a probe. In the actual experiment, the probe's tip is embedded a few microns into the otolithic membrane. Note than in C and D, the probes have not been drawn to scale; in particular, the cantilever arms are typically a few hundred microns in length.