Burst onset timing is variable in individual neurons. Burst onset timing variability (A) is weakly, although significantly, anticorrelated with subsequent endogenous bursting (Kendall tau = −0,16; P < 0.0001). B: periburst first nth (for n = 1, 3, and 5; second axis) spike times for 10 randomly selected strong pacemakers confirms that burst onset in individual bursters can follow the population burst onset on many cycles.