Figure 7.

Most of the experimentally observed inter-trial variability can be explained by synapse amplitude variability, spontaneous events and measurement noise. The average (n = 18) RMSE_rel of inter-trial variability of spontaneous activity alone (including measurement noise), derived from experimentally recorded membrane potential fluctuations prior to stimulation, was calculated to be 22% (spontaneous), which is approximately half of the experimentally measured RMSE_rel (experiments). Simulated membrane potential fluctuations with realistic synaptic variability values alone (without noise) produced a RMSE_rel of 27% (stimulated). When spontaneous activity – including spontaneous presynaptic events, spontaneous releases and measurement noise – was added (RMSE_rel = 51%), more than 85% of the average amplitude variability was explained. Red cross denotes one outlier.