Occurrence of spontaneous minis at individual synapses. A, Minis recorded from one hippocampal synapse with synaptic loose patch. Notice how trains of minis, each one marked by a dot, can occur in short intervals of time (right, expanded traces). B, Log-binned histogram of mini-intervals from the same single-bouton recording experiment as in A. Multiple exponentials were always required for best fit of interval distributions, indicating a divergence from simple Poisson statistics. The histogram presented was best fitted by the sum (solid line) of three decaying exponentials (dotted lines) (p < 10⁻⁴, τ_fast = 42.18 msec, τ_medium = 402.24 msec, τ_slow = 21.54 sec; relative areas, 51, 33, and 16%; n = 165 events). C, Ensemble plot from n = 6 single-synapse experiments illustrating the lack of inhibition at very short intervals. Each bin plots the mean ± SD of the difference between the bin entry and the fit value (error bars). The dotted lines plot the 5% confidence limits for a single-exponential distribution obtained with Monte Carlo random sampling methods (n = 11).