Fig. 3. Emulation of synaptic plasticity and memory behaviors at 450 °C.

a Schematic diagram of a biological synapse. b Paired-pulse facilitation (PPF) index as a function of pulse interval (Δt). Inset: PPF measurement protocol, where A₁ and A₂ denote the amplitudes of the postsynaptic current (PSC) triggered by the first and second light pulses, respectively. c–f Short-term plasticity (STP) to long-term plasticity (LTP) transition at 450 °C induced by increasing pulse number (c), intensity (d), frequency (e), and width (f). g Schematic diagram of the “learning-forgetting-relearning” processes based on short-term memory (STM) and long-term memory (LTM). h Four consecutive “learning-forgetting-relearning” cycles measured at 450 °C, where ∆I_1-4 represent the current remnants extracted at the end of each forgetting phase, and the blue shaded areas represent the light stimulation periods.