Synaptors connect silicon and brain neurons in hybrid network. (a) Sketch of the main components of the hybrid circuit and of the synaptors. ANpre and ANpost are silicon spiking neurons of a VLSI network28,35 (SNN), while MR1 and MR2 are Pt/TiOx/Pt memristors36. The capacitive Al/TiO2 electrode, CME, is an element of the multi electrode array, CMEA (Supplementary Fig. 1) where rat hippocampal neurons are cultured on the functionalized surface of the TiO2 thin film. One neuron is contacted by a patch-clamp pipette, P, for intracellular whole-cell recording. The two synaptors, ABsyn and BAsyn, connect the ‘presynaptic’ silicon neuron (ANpre) to the brain neuron (BN), and BN to the ‘postsynaptic’ silicon neuron, ANpost. The two memristors, MR1 and MR2, emulate plasticity in the two synaptors, whereas electronics-to-BN and BN-to-electronics signal transmission are mediated by the CME and the patch-clamp electrode. (b) Operational scheme. In ABsyn, changes in MR1 resistive states, R(t), are driven by ANpre and BN depolarisations rates according to an approximated BCM plasticity rule (Supplementary Table 1 and Supplementary Fig. 3) resulting in either LTP (red), LTD (blue) or no change. MR1 resistive states are translated into weighted voltage stimuli. These are delivered to BN through the CME capacitance (CCME) causing EPSP-like depolarisations, in turn leading to action potential firing (Supplementary Fig. 1). Similarly, in BAsyn, BN spikes are recorded by the patch-clamp electrode through its resistance, Rp, threshold-detected and then transmitted to ANpost as current injections that are adjusted via MR2 weights.