Figure 4.

(a) An example of pulsing scheme for the realization of STDP learning rule. (b) A schematic illustration of synapse circuit to achieve dual coding learning scheme. (c) A typical STDP learning rule emulated using iron oxide memristor at 10 kHz presynaptic firing frequency. (d) A summary of learning rule integration when varying presynaptic firing frequency. It shows that STDP learning rule only happens at the moderate frequency region and other regions are dominated by the SRDP learning rule.