Fig. 1: Neuromorphic spiking system emulating sensory coding and neuromodulation.

a Illustration representing sensory coding of light stimuli by the afferent neuron and dopamine-regulated neuromodulation by the interneuron. b Schematic of the modular neural pathway including the neuromorphic spiking neuron consisting of an inverter pair and a switch with their corresponding active materials. For sensory coding a physical receptor (an ambient light sensor) is connected and for neuromodulation a synaptic modulator, comprising a biohybrid synapse using PEDOT:PSS, is employed. c Sensory coding of light using an ambient light sensor as physical receptor showing an increasing spike frequency of the afferent neuron output with increasing light intensity and corresponding sensor output voltage (see Supplementary Discussion 1). The output frequency shows a 137% modulation with respect to the spike frequency (0.10 Hz) of the first (low) light condition. d Neuromodulation regulated by dopamine using the synaptic modulator circuit. The graph shows the input to the synaptic modulator and the modulation of the interneuron spike frequency depending on the dopamine concentration. The synaptic modulator output increases due to the oxidation of DA (red). The dotted lines are the experimental curves showing the presence of the spiking input. The solid lines emphasise the synaptic weight modulation. The spike frequency modulations are 28% and 26% for 0.1 mM DA (dark red) and 0.025 mM DA (light red), respectively, with respect to the spike frequency of PBS (black; 0.10 Hz).