Meeting Abstract

131.4  Monday, Jan. 7  Emergence of a Neuromechanical Phase Lag in a Resistive Force Dominated Medium DING, Y*; SHARPE, S.S.; GOLDMAN, D.I.; Georgia Tech; Georgia Tech; Georgia Tech dingyang@gatech.edu

Undulatory locomotion is a common gait used by organisms in fluids, on land, andeven within sand. This mode of locomotion relies on propagation of a traveling wave of body bending, producing thrust which propels the animal in the opposite direction. Many previous studies have shown that the wave of muscle activation progresses faster than the wave of curvature. This leads to an increasing phase lag between activation and curvature at more posterior segments, known as the neuromechanical phase lag. A number of multi-parameter neuromechanical models have been proposed to account for the phase lag, but are difficult to analyze to reveal basic principles. Here we demonstrate that in addition to kinematic similarities, undulatory sand-swimming of the sandfish lizard also neuromechancially resembles swimming in fluids. Using the simplest model of undulatory sand-swimming consisting of prescribed kinematics and granular resistive forces, we show that with no fitting parameters, the biological measurements quantitatively match model predicted phase lag between the local body curvature and torque exerted by granular resistive forces. Analyzing the model reveals the dominant mechanism responsible for the phase lag: different integration length over a traveling force pattern for different positions along the body. Our results demonstrate that movement in the non-inertial resistive force dominated granular mediumis a simple system for studying neuromechanics, allowing detailed comparisons between experiment and theory. Such comparison can give insight into principles that generate the neuromechanical phase lags in other environments.