Fast-rising mEPSCs at thalamocortical synapses are mediated by a single component, where as evoked EPSCs at the same input a redual component. A, Example averaged eEPSC (in 2.5 mm Ca²⁺, 0 mm Sr²⁺) and double-exponential fit to the decay (gray). All data in A-D are from the same cell. B, Examples of two traces (not averaged) in the presence of Sr²⁺ (0 mm Ca²⁺, 2 mm EGTA) showing the synchronized eEPSC followed by evoked mEPSC_fast. C, Aligned and superimposed mEPSC_fast events (top) and average of these (bottom). The gray line is a single-exponential fit to the decay. D, Averaged mEPSC_fast (same trace as in C) and averaged eEPSC (same trace as in A) from the same cell aligned, peak scaled, and superimposed. The gray lines are single (for mEPSC_fast) and double (for eEPSC) exponential fits to the decay. E, Summary data of τ_decay plotted versus 10-90% rise time for mEPSC_fast (filled circles; n = 42), for dual-component eEPSCs (open diamonds, fast τ_decay; filled squares, slow τ_decay; n = 29), and for eEPSC with only a fast component (open triangles; n = 13).