Figure 4.

Simultaneous fluctuations about the mean period (a cycle period minus the mean period, measured in μs) of (A) EOD (EOD [i]) and (B) an impaled Pn neuron (Pn [i]). (C) EOD [i] vs. Pn [i] does not show obvious direct command by this neuron of cycle-by-cycle EOD fluctuations. (D) EOD [i+1] plotted against EOD [i]. Seen in many fish, a short period tended to be followed by a long one and vice versa, producing a bimodal distribution. (E) Pn [i+1] vs. Pn [i] plot also is skewed, with short periods tending to follow long ones and vice versa, although the resulting distribution is not bimodal. The common tendency to the same skewing suggests that the Pn neurons could collectively command cycle-by-cycle fluctuations about the mean period.