Abstract
Rodents use their whiskers to locate nearby objects with an extreme precision. To perform such tasks, they need to detect whisker/object contacts with a high temporal accuracy. This contact detection is conveyed by classes of mechanoreceptors whose neural activity is sensitive to either slow or fast time varying mechanical stresses acting at the base of the whiskers. We developed a biomimetic approach to separate and characterize slow quasi-static and fast vibrational stress signals acting on a whisker base in realistic exploratory phases, using experiments on both real and artificial whiskers. Both slow and fast mechanical inputs are successfully captured using a mechanical model of the whisker. We present and discuss consequences of the whisking process in purely mechanical terms and hypothesize that free whisking in air sets a mechanical threshold for contact detection. The time resolution and robustness of the contact detection strategies based on either slow or fast stress signals are determined. Contact detection based on the vibrational signal is faster and more robust to exploratory conditions than the slow quasi-static component, although both slow/fast components allow localizing the object.
Highlights
We continue this section by presenting how both quasi-static and dynamical components of the base torque vary with the radial distance d and by giving a detailed comparison of our measurements with the biomechanical model described earlier
To reproduce natural exploration tasks used by a rodent to detect and localize an object in its vicinity, a second set of experiments have been performed and are reported in the section “Whisking regime.”
These consisted in approaching an object to an oscillating whisker to mimic both the body motion and the whisking behavior
Summary
Rodents use their facial whiskers (vibrissa) to locate objects (Krupa et al, 2001; Knutsen, 2006; Mehta et al, 2007; O’Connor et al, 2010), apprehend their shape (Brecht et al, 1997; Polley et al, 2005; Anjum et al, 2006) and texture (Carvell and Simons, 1990; Lottem and Azouz, 2008; Boubenec et al, 2014) with an extreme precision. In a localization task (Krupa et al, 2001; Pammer et al, 2013; Voigts et al, 2015), contacts occur as a result of both rodent’s body or head movements, combined with periodic whisker retraction/protraction cycles elicited by an active motor pattern called whisking. SA mechanoreceptors respond to a steady applied stress while FA mechanoreceptors are triggered by rapid events. Such rapid events, produced for instance by contact-detachment (Szwed et al, 2003; Lottem and Azouz, 2009) and frictional stick-slip (Ritt et al, 2008) trigger enhanced neural activity along the trigeminal pathway
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