Figure S18. (a) Excitatory post-synaptic currents of the vertical type memristors with Mw = 10000 and 23000 gmol-1, under electric stimuli. (b) Paired-pulse facilitation (PPF) index as a function of a time interval value between two successive voltage pulses (1.5 V, 10 μs), in the vertical type memristor with Mw = 23000 gmol-1.