Regional variability in spontaneous firing properties of dimorphic terminals. (A and B) Representative examples of dimorphic terminals that fired with regular (A) and irregular (B) patterns. (C) Percentage of dimorphic terminals that were spontaneously active at rest as a function of region. (D) Firing rate was calculated for calyx terminals with spontaneous activity. The firing rate was significantly lower in the central region than in the periphery. Error bars indicate mean ± SEM. (E and F) Peripheral dimorphic terminals fired with greater regularity than centrally located dimorphic terminals. The CV was calculated by dividing the standard deviation of the interspike interval by the mean. Regular is indicated by the broken line at <0.25. *, P < 0.05. The number of samples is shown inside the bars for each condition.