Figure 5.

Zero contours of the muscle torque, β(u, t) (blue), and body curvatures, κ(u, t) (red), obtained from simulations in an agar-like medium and E = 100 kPa. Both positive and negative zero-crossings are included. (a) Under a model of feed-forward (CPG) control, the latency between activation and body bend grows linearly along the body. (b) Under a model of proprioceptive control with a diminishing proprioceptive range in the posterior half of the body, the curvature and muscle activation are tightly coupled in the anterior half; the increasing phase lag towards the tail arises from an accelerated neuromuscular wave speed of muscle torque in the posterior half of the body. (c) Kymograms of the body curvature corresponding to (b). Black and magenta lines show peak negative and positive values of muscle activation β(u, t), along the body, respectively.