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INNOVATIVE METHODOLOGY

Unsupervised Whisker Tracking in Unrestrained Behaving Animals

¹Undergraduate Program in Mathematics, University of Heidelberg, Heidelberg, Germany; ²Laboratory of Neural Circuits and Plasticity, Section of Neurobiology, University of Southern California, Los Angeles, CA; and ³Department of Cell Physiology, Max Planck Institute for Medical Research, Heidelberg, Germani

Submitted 5 January 2008; accepted in final form 3 May 2008

Understanding how whisker-based tactile information is represented in the nervous system requires quantification of sensory input and observation of neural activity during whisking and whisker touch. Chronic electrophysiological methods have long been available to study neural responses in awake and behaving animals; however, methods to quantify the sensory input on whiskers have not yet been developed. Here we describe an unsupervised algorithm to track whisker movements in high-speed video recordings and to quantify the statistics of the tactile information on whiskers in freely behaving animals during haptic object exploration. The algorithm does not require human identification of whiskers, nor does it assume the shape, location, orientation, length of whiskers, or direction of the whisker movements. The algorithm performs well on temporary loss of whisker visibility and under low-light/low-contrast conditions even with inherent anisotropic noise and non-Gaussian variability in the signal. Using this algorithm, we define the speed [protraction (P), 1,081 ± 322; retraction (R), 1,564 ± 549 °/s], duration (P, 34 ± 10; R, 24 ± 8 ms), amplitude (P = R, 40 ± 13°), and frequency (19 ± 7 Hz) of active whisking in freely behaving mice. We furthermore quantify whisker deflection induced changes in whisking kinematics and calculate the statistics (i.e., speed, amplitude and duration) of whisker touch and finally show that whisker deprivation does not alter whisking kinematics during haptic exploration.

This article has been cited by other articles:

				M. C. Stuttgen, S. Kullmann, and C. Schwarz Responses of Rat Trigeminal Ganglion Neurons to Longitudinal Whisker Stimulation J Neurophysiol, October 1, 2008; 100(4): 1879 - 1884. [Abstract] [Full Text] [PDF]