Complex textures evoke resonance in vibrissae. A, Experimental setup of the texture wheel driving vibrissa motion. Under natural conditions, rats may contact the stimulus at the tip, in the middle, or close to the base of the vibrissa (Brecht et al., 1997; Hartmann, 2001) and frequently sample textures with the vibrissae pressed against the sensory surface (one study observed typical contact points at ∼15 mm from the face) (Carvell and Simons, 1990, 1995). This stimulation emulates features of this configuration, because the vibrissae were pinned against the complex surface with a contact point on the wheel at ∼15 mm from face. B, C, The model (B) and experimental (C) measurements of the rms temporal spectra of the motion of an A4 vibrissa driven by a periodic grating at different velocities. The texture was presented at velocities from 155 to 2200 mm/sec. The brightness of the color scale represents the predicted amplitude of the motion of the vibrissa, given the texture presented at a specific velocity. C, Corresponding measurements were made with a grating mounted on a wheel and spun past an in vivo A4 vibrissa. The velocities ranged from 200 to 2000 mm/sec. Note the presence of a horizontal band (resonant motion) and diagonal bands (prominent driving frequencies of sandpaper texture) (see Materials and Methods for details). D, Amplitude temporal spectrum of the A4 vibrissa in response to the periodic grating (same as in C) and in response to a smooth texture presented by the wheel at 440 and 880 mm/sec (the measured regions are marked with vertical bands in C). E, Trace of vibrissa motion when presented with the periodic grating at 220, 440, and 660 mm/msec. Note the prominent increase in vibrissa motion at the FRF during contact with the textured stimulus (red line marks texture onset) at 440 mm/msec, at which the velocity of the grating applied the FRF to the vibrissa. F, G, The model and experimental measurements of the temporal spectra of the motion of the C4 vibrissa when presented with sandpaper (40 grit) at different velocities. Same axes as in B and C. H, Power spectra of the C4 vibrissa in response to the sandpaper and in response to a smooth texture presented (similar to D) at 715 and 1375 mm/sec (vertical bands in G).