Figure 4. Implementation of SRDP in the inorganic memristor.

(a) Dependence of synaptic modification on the frequency of the postsynaptic firing rate induced by 50 repetitive stimulations. For postsynaptic firing rates below f_θ (50 kHz), the synapse is depressed, while synaptic potentiation can be observed beyond f_θ. The presynaptic rate is fixed at 50 kHz. (b) Changes in synaptic conductance following potentiation (upper) or depression (lower) stimulation. The synaptic efficacy remains stable over 2200 s, indicating a long-term modification. In the tests, all spikes are triangle voltage pulses with 5 μs rising time and 5 μs falling time. The voltage amplitudes are 1.2 V for the presynaptic spikes and 0.8 V for the postsynaptic spikes.