A Mixed-Signal Structured AdEx Neuron for Accelerated Neuromorphic Cores

Here we describe a multi-compartment neuron circuit based on the Adaptive-Exponential I&F (AdEx) model, developed for the second-generation BrainScaleS hardware. Based on an existing modular Leaky Integrate-and-Fire (LIF) architecture designed in 65 nm CMOS, the circuit features exponential spike generation, neuronal adaptation, inter-compartmental connections as well as a conductance-based reset. The design reproduces a diverse set of firing patterns observed in cortical pyramidal neurons. Further, it enables the emulation of sodium and calcium spikes, as well as N-Methyl-D-Aspartate (NMDA) plateau potentials known from apical and thin dendrites. We characterize the AdEx circuit extensions and exemplify how the interplay between passive and non-linear active signal processing enhances the computational capabilities of single (but structured) on-chip neurons. Keywords—Analog integrated circuits, Neuromorphic, Leaky, Integrate-and-Fire, 65 nm CMOS, Spiking, Bursting, Neuron, Adaptation, Exponential, LIF, AdEx, Multi-compartment, Dendrites, NMDA