Natural Whisking. Focus on 'Variability in Velocity Profiles During Free-Air Whisking Behavior of Unrestrained Rats

摘要

The rat whisker system is inherently an active sensory system (Mehta et al. 2007). The whiskers move through space to locate and palpate objects in the environment, varying amplitude, frequency and angular direction as they do so (Fee et al. 1997). The earliest studies by Welker (1964) described coordination between vibrissae, nose, head, and sniffing movements. Importantly, Welker suggested that the animal's whisking behavior is dependent on the task and that whisking during exploratory behaviors was different from whisking during discriminative behaviors. Discrimination is an important sensory task, and several studies have examined whisking behaviors during tactile-discrimination tasks that necessarily require intense training of the animals and constrain the way in which the animal contacts the discriminandum (Carvell and Simons 1990, 1995; Guic-Robles et al. 1989; Harvey et al. 2001). Therefore the type of stimulation presented to the animal was far more limited than the broad range of trajectories, amplitudes, and velocities in which rats might typically move their whiskers (Berg and Kleinfeld 2003; Bermejo et al. 1996, 2002, 2005; Brecht et al. 1997; Gao et al. 2001, 2003; Hattox et al. 2003; Mitchinson et al. 2007; O'Connor et al. 2002; Sachdev et al. 2001-2003; Simons 1983, 2003). This in turn limits the information conveyed to the brain, limiting our understanding of neural encoding strategies. The relationship between the design of sensory organs, the kinematics of how those sensory organs are used by the organism and the neural substrates within the brain that process this information are not well understood. A major reason for this is a lack of understanding of how animals naturally explore their environment. A recent article by Towal and Hartmann (2008) provides an important examination of natural whisker movements as a significant first step to understanding the kinematics of how the rat uses its whiskers in space to find targets#