Figure 11.
Simulations suggest that spillover currents increase the reliability of MF signaling. Simulated EPSCs with quantal variance and spillover at –76 mV for three different MF-GC synaptic connections with mean amplitudes that were small (A1; N = 1, PR = 0.22, and QP =–14.7 pA), similar to the mean (B1; N = 5, PR = 0.46, and QP =–16.7 pA), and large (C1; N = 9, PR = 0.42, and QP =–16.5 pA). Values for quantal variability were CVQS = 0.26 and CVQII = 0.31. The gray traces in each panel show 30 individual EPSCs and failures; the black trace is the average. A2, B2, and C2 show simulated EPSPs for the same currents as in A1, B1, and C1 for a passive single-compartment model with a baseline membrane potential of –76 mV. A3, B3, and C3 show PV > Vthreshold as a function of the baseline voltage for the connections simulated above. Each symbol represents the probability over 1000 trials; filled circles show the relationship without spillover, and open triangles show the relationship in the presence of spillover. A4, B4, and C4 show the relationship between the SD of the times when the EPSC crossed a –50 mV threshold and the baseline voltage; each symbol represents the SD calculated over 1000 trials.