Experimental results of 6 neuron VLSI circuit of lamprey unit pattern generator

The lamprey, an eel-like fish, has 100 segments in the spinal cord. Each segment, called the unit Pattern Generator (uPG), is capable of generating self-sustained oscillations for locomotion, i.e. swimming. The authors have designed, built, and tested an electronic circuit model of the uPG using analog VLSI CMOS circuits. Their neuromorphic single-segment model utilizes 6 neurons, 4 excitatory synapses, 8 inhibitory synapses, and 6 tonic synapses with simplified biophysical properties. In this paper, the authors present the experimental results of the chip and compare to the simulated chip behavior. They present the operation under varying conductances, then consider the entrainment of the segment to an external signal with varying frequency and magnitude.