Figure 7.

Experiments on the network model. Following a stimulus (↓), swimming occurs (A) if all marginal zone axons have the same dorsoventral distributions as sensory pathway dlas, (B, C) CPG neuron dendrites are extended so they are contacted by all marginal zone axons, but synapse formation probability is reduced to 0.25. C shows spike times in all neurons and voltage traces from a subset. D, Longer model (as in B) shows clear head-to-tail delay in motoneuron spike firing (red lines). Earliest spikes are at ∼1100 μm (dotted line). E, Head-to-tail delay in motoneuron spikes (○ right and ● left sides; error bars are SDs). Regression line from 1100 μm gives a mean delay of 4.4 ms mm⁻¹; from 6 swimming cycles in 12 networks.