AR strength depended on the type of synaptic connections.

<p>(A) Overlay of unitary IPSCs in the postsynaptic PC evoked by single APs in the presynaptic FS neuron. (B) Example current traces (same FS-PC pair as in A) showing the dependence of AR strength at both autaptic and FS-PC synaptic connections on the stimulus intensity. Box, expanded trace for clarity. Note that AR could occur during (arrows) and after (arrowheads) the train of stimulation. (C) Group data showing the dependence of AR strength on the number and the frequency of presynaptic APs in FS-PC pairs (two-way ANOVA analysis, <i>p</i><0.001). (D) Cumulative frequency distribution indicates that FS autapses had longer PT-AR duration and more events than FS-PC synapses (<i>p</i><0.001 for both parameters). (E) Group data from FS-PC pairs (<i>n</i> = 22) that exhibited both autaptic and synaptic connections. (F) Group data showing that FS autapses had significantly higher PT-AR frequency than FS-PC synapses. (G) Bar plot of the normalized PT-AR duration (normalized to the average peak amplitude of unitary IPSCs). This normalization reveals the dependence of PT-AR duration on the synaptic strength. (H) Plot of the PT-AR duration as a function of synaptic strength. One outlier data point (688, 238) from autaptic connections has been excluded. Solid lines are linear fits (Black: r = 0.50, <i>p</i> = 0.07; red, r = 0.57, <i>p</i><0.001). * <i>p</i><0.05; ** <i>p</i><0.01; *** <i>p</i><0.001.