Perception is usually an active process by which action selects and affects sensory
information. During rodent active touch, whisker kinematics influences how objects
activate sensory receptors. In order to fully characterize whisker motion, we
reconstructed whisker position in 3D and decomposed whisker motion to all its degrees
of freedom. We found that, across behavioral modes, in both head-fixed and freely
moving rats, whisker motion is characterized by translational movements and three
rotary components: azimuth, elevation, and torsion. Whisker torsion, which has not
previously been described, was large (up to 100 degrees), and torsional angles were
highly correlated with whisker azimuths. The coupling of azimuth and torsion was
consistent across whisking epochs and rats and was similar along rows but
systematically varied across rows such that rows A and E counterrotated. Torsional
rotation of the whiskers enables contact information to be mapped onto the
circumference of the whisker follicles in a predictable manner across
protraction-retraction cycles.