Figure 1. Ex vivo Vibrissa Micro-Motions.

A. (left) A torque motor was used to sweep vibrissae at realistic ‘whisk’ speeds across sensory surfaces. (right) Still frame of a vibrissa contacting sandpaper. Angular position was measured by the intersection of vibrissae with the red circle. B. The average of 6 vibrissa micro-motion traces shown for three sweep speeds over a periodic grating. Movement of the vibrissae at an intermediate sweep speed, 630°/sec, recruited larger amplitude oscillations than movement at slower or higher sweep speeds. This selective amplification indicates vibrissa resonance tuning, and highlights the impact that variations in sweep speed can have on the form of micro-motions generated by surface contact. C. Schematic of predicted dependence between intrinsic elastic properties of the vibrissa (fundamental resonance frequency, horizontal line) and the sweep speed of vibrissa motion (x axis) across frequency (y axis). Sweeping the vibrissa across a texture with given spatial frequencies will induce temporal responses (diagonal lines), with amplification (filled disk) at an appropriate sweep speed. D. Micro-motions from a vibrissa swept at two different velocities over sandpaper, with a fixed distance of 24.5mm from the base (vibrissa length 32mm). Each panel shows 8 repeated measurements of the same sweep conditions. The time bases are scaled in the ratio 540/720, to align micro-motions generated by the same surface features. Vibrissae generated micro-motion patterns with high consistency across sweeps, but micro-motion patterns changed substantially with a change in sweep speed.