The Rat Vibrissal Array as a Model Sensorimotor System

The rat whisker (vibrissal) system has neural processing pathways that are analogous to human tactile pathways through the spinal cord. Rats use rhythmic (5-25 Hz) movements of their whiskers to tactually extract object features, including size, shape, orientation, and texture. In this talk, I will describe our efforts to characterize whisker mechanical properties and to determine the set of mechanical variables that could potentially be sensed by the rat. We have also developed a hardware array of artificial whiskers that makes use of these variables to successfully extract 3-dimensional object features. On the behavioral side, we have developed a laser light sheet to visualize whisker-object contact patterns during natural exploratory behavior and have used this technique to examine the relative roles of head and whisker movements in generating patterns of mechanosensory input across the array during natural exploratory sequences. Finally, we are developing a simulation environment that integrates our knowledge of whisker mechanics with our knowledge of head and whisker motion to enable the user to model the rat's interactions with various objects in the environment. Our goal is to predict the contact patterns – and resulting forces and moments – at each whisker base for a given exploratory sequence, and then to predict the resulting responses of trigeminal ganglion neurons.