Figure 9.

Timing of activation of motor neurons B7 and B10 affects magnitude and speed of inward movement and dorsal tube rotation. A, The B7 and B10 neurons were both activated simultaneously, and the magnitude of the inward movement and dorsal rotation was measured. B, The B7 neuron was activated 1 s before the B10 neuron. C, The B7 neuron was activated 2 s before the B10 neuron. The largest, fastest, and smoothest inward movement and dorsal rotation occurred when B7 was activated 1 s before B10 (n = 4). At a separation of 0 s between the onset of B7 and B10, the net inward movement was 4.8 ± 0.5 mm. At a separation of 1 s, the net inward movement was 6.5 ± 0.6 mm. At a separation of 2 s, the net inward movement was 4.5 ± 0.6 mm. Overall ANOVA was significant (p < .002), and the net inward movement with 1 s separation was significantly greater than either 0 s separation (p < 0.004) or 2 s separation (p < 0.003). The net inward movements at 0 s separation and 2 s separation were not significantly different from one another. D, A scatter plot of average angular velocity (in degrees per second) versus average inward velocity (in millimeters per second) for delay of 0 s from B7 to B10 activation (black dots), 1 s (open circles), and 2 s (gray dots). Note that the data from the 1 s delay are significantly separated from the other two datasets. Overall MANOVA is significant (p < 0.001), and post hoc differences between 1 s and either 0 or 2 s are significant (p < 0.001), but differences between 0 and 2 s are not.