Neurodynamics in simple cyclic Hopfield neural network under external electromagnetic radiation and stimulating current inputs

External stimuli can influence the electrical activities of neurons, inducing complex and diverse neurodynamic behaviors through coordination and interaction among neurons. This article investigates the neurodynamics of a simple cyclic Hopfield neural network (SCHNN) with unidirectional connections and no autapse, under external electromagnetic radiation and stimulating current inputs. Numerical analyses show that, when SCHNN is exposed only to electromagnetic radiation, it has eight unstable equilibria and can produce homogeneous/heterogeneous multistability, amplitude control and different types of firing patterns, e.g., periodic/chaotic spiking and bursting firing. When SCHNN is affected jointly by electromagnetic radiation and stimulating current inputs, it exhibits diverse types of firing multistability, such as resting and periodic spiking as well as chaotic and periodic spiking. Interestingly, neurons in SCHNN also exhibit controllable frequency bursting firing behavior with varying electromagnetic radiation parameters in huge scales. Finally, a digital hardware implementation platform is designed and physically realized to reproduce the neurodynamics observed from numerical simulations.