Topography of whisking II: Interaction of whisker and pad

Abstract

The peripheral effector system mediating rodent whisking produces protraction/retraction movements of the whiskers and translation movements of the collagenous mystacial pad. To examine the interaction of these movements during whisking in air we used high-resolution, optoelectronic methods for two-dimensional monitoring of whisker and pad movements in head-fixed rats. Under these testing conditions (1) whisker movements on the same side of the face are synchronous and of similar amplitude; (2) pad movements exhibit the characteristic ‘exploratory’ rhythm (6–12 Hz) of whisking but their movements often have a low frequency (1–2 Hz) component; (3) Pad movements occur in both antero-posterior and dorso-ventral planes but there are considerable variations in the amplitude and topography of movement parameters in the two planes. We conclude that (a) both whisker and pad receive input from a common central rhythm generator; (b) differences in whisker and pad amplitude and topography probably reflect differences in the biomechanical properties of the structures receiving that input; (c) pad movements make a significant contribution to the kinematics of whisking behavior and (d) the two-dimensional nature of pad translation movements significantly increases the rat's flexible control of its mobile sensor.

• Whisking
• motor system
• movement
• whisker
• pad
• topography

Notes

Notes

1. A recent study from Ahissar's laboratory confirms the fact that measurements within the length of the marker do not introduce errors into calculations of whisker kinematics (Knutsen et al. 2004).

2. The laser beam of the monitoring device intersects both the pad and whisker markers at the same distance from the face.

3. Although a whisker position of 90° is arbitrarily taken as the midpoint of the whisking range during calibration, in the behaving animal pad movements may shift the starting point over time.