Electrophysiological characteristics of mature iPSC-derived neurons. (A) Capacitance, resting membrane potential (RMP), action potential (AP) firing threshold, and voltage peak were identical across all neurons analyzed (P >0.05, Kruskal-Wallis test); error bars indicate S.E.M. (B) Representative traces of AP trains triggered by a 500-ms depolarizing current at the indicated intensities. Transverse dotted lines demark 0 mV membrane potential. Scale bars: 20 mV vs. 100 ms. (C) Action potential (AP) decrement at current intensities triggering >10 APs calculated as a percentage: 10th/1st AP amplitude. Control vs. D1-1 (P = 0.078) and D1-6 (*P = 0.045, ANOVA); D1-1 vs. D1-6 (P = 0.839) (D) Total number of APs during the 500-ms stimulation period vs. current injection intensity. When exposed to strong current injections, both patient-derived cell lines produced significantly fewer APs compared to the control (the slope of AP numbers at ≥50 pA, P = 0.0102 and 0.0011 for D1-1 and D1-6, respectively, ANCOVA, *P <0.05 for D1-6 only, **P <0.05 for both D1-1 and D1-6, Wilcoxon rank-sum test).