Figure 2.

Fictive swimming motor pattern in embryos. A, Schematic on the left illustrates the position from which motor nerve recordings illustrated on the right are taken (7th and 13th body segments). An electrical stimulus delivered to the tail was used to elicit swimming (artifact at asterisk). Top right, Single episode of swimming on a slower time base; bottom right, illustration, on a faster time base, of motor bursts that would drive cyclical bending. Transparent gray boxes illustrate the head-to-tail delay of motor bursts. B, Plot of motor nerve burst frequency (measured from the tail) with respect to the cycle in the episode from three electrically evoked episodes in the same embryo. C, Plot of head–tail motor burst delay versus cycle period in a single embryo. These data are compiled from one episode of electrical stimulus-induced swimming from one embryo. Correlation values: r = −0.08, p = 0.10, n = 406 cycles.