TY - JOUR
T1 - Biomechanical models for radial distance determination by the rat vibrissal system
AU - Birdwell, J. Alexander
AU - Solomon, Joseph H.
AU - Thajchayapong, Montakan
AU - Taylor, Michael A.
AU - Cheely, Matthew
AU - Towal, R. Blythe
AU - Conradt, Jorg
AU - Hartmann, Mitra J Z
PY - 2007/10
Y1 - 2007/10
N2 - Rats use active, rhythmic movements of their whiskers to acquire tactile information about three-dimensional object features. There are no receptors along the length of the whisker; therefore all tactile information must be mechanically transduced back to receptors at the whisker base. This raises the question: how might the rat determine the radial contact position of an object along the whisker? We developed two complementary biomechanical models that show that the rat could determine radial object distance by monitoring the rate of change of moment (or equivalently, the rate of change of curvature) at the whisker base. The first model is used to explore the effects of taper and inherent whisker curvature on whisker deformation and used to predict the shapes of real rat whiskers during deflections at different radial distances. Predicted shapes closely matched experimental measurements. The second model describes the relationship between radial object distance and the rate of change of moment at the base of a tapered, inherently curved whisker. Together, these models can account for recent recordings showing that some trigeminal ganglion (Vg) neurons encode closer radial distances with increased firing rates. The models also suggest that four and only four physical variables at the whisker base - angular position, angular velocity, moment, and rate of change of moment - are needed to describe the dynamic state of a whisker. We interpret these results in the context of our evolving hypothesis that neural responses in Vg can be represented using a state-encoding scheme that includes combinations of these four variables.
AB - Rats use active, rhythmic movements of their whiskers to acquire tactile information about three-dimensional object features. There are no receptors along the length of the whisker; therefore all tactile information must be mechanically transduced back to receptors at the whisker base. This raises the question: how might the rat determine the radial contact position of an object along the whisker? We developed two complementary biomechanical models that show that the rat could determine radial object distance by monitoring the rate of change of moment (or equivalently, the rate of change of curvature) at the whisker base. The first model is used to explore the effects of taper and inherent whisker curvature on whisker deformation and used to predict the shapes of real rat whiskers during deflections at different radial distances. Predicted shapes closely matched experimental measurements. The second model describes the relationship between radial object distance and the rate of change of moment at the base of a tapered, inherently curved whisker. Together, these models can account for recent recordings showing that some trigeminal ganglion (Vg) neurons encode closer radial distances with increased firing rates. The models also suggest that four and only four physical variables at the whisker base - angular position, angular velocity, moment, and rate of change of moment - are needed to describe the dynamic state of a whisker. We interpret these results in the context of our evolving hypothesis that neural responses in Vg can be represented using a state-encoding scheme that includes combinations of these four variables.
UR - http://www.scopus.com/inward/record.url?scp=35348871944&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=35348871944&partnerID=8YFLogxK
U2 - 10.1152/jn.00707.2006
DO - 10.1152/jn.00707.2006
M3 - Article
C2 - 17553946
AN - SCOPUS:35348871944
SN - 0022-3077
VL - 98
SP - 2439
EP - 2455
JO - Journal of neurophysiology
JF - Journal of neurophysiology
IS - 4
ER -