(a) Schematic of a synaptic Si-NC phototransistor. (b) IPSC induced by a 1342 nm laser spike. (c) IPSC (EPSC) induced by a –50 mV (+50 mV) electrical spike. (d) Dependence of the STDP-induced synaptic weight change (ΔW) on the interval time between the presynaptic and postsynaptic spikes (Δt_pre-post). ΔW is calculated by using ΔW = ΔPSC/PSC1, where ΔPSC results from the subtraction of the postsynaptic current of the first spike (PSC1) from that of the last spike. (e) Implementation of taste aversion learning with a synaptic Si-NC phototransistor. (f) Example images in the MNIST database after the binarization with a pixel threshold of 50. (g) The architecture of the SNN. (h) Receptive fields of all output neurons in the network. Reproduced with permission from Ref. [99]. Copyright 2019, Elsevier Ltd.