Fig. 4. Biological neuron behavior modeling and experimental measurement.

a Four dynamical events during the electrical impulse (1–4) are marked. 1 Resting state, both Na⁺ and K⁺ channels are closed. 2 Depolarization, the hyperpolarization caused by the activation of Na⁺ channels make the membrane potential move in the negative direction. 3 Re- and hyper-polarization, the depolarization caused by the activation of K⁺ channel drives the membrane potential to the positive direction. 4, Refractory period, neurons are recovering and have no response to another stimulus. b–d The relationship between input voltage and output voltage of FN neuron circuit. e The relationship between effective voltage and output frequency when the series inductance is different. f–n The experiment demonstrated 9 biological neuron spike behaviors in FN neuron circuits based on NDR memristors. f phasic spiking, g anodal break excitation, h spike accommodation, i subthreshold oscillations, j class 1 excitable, k all or nothing firing, l tonic bursting, m refractory period, n accommodation.