Effect of spatial facilitation on neural network excitability

The time evolution of an asymmetrical form of the Hopfield neural network was simulated. The noise assigned to each neuron to represent spontaneous fluctuations of membrane potential had a translated gamma distribution. As a result, in comparison with the generally accepted Gaussian noise with the same mean and standard deviation, for each neuron the instantaneous sum of the noise and the input signals from other neurons could exceed a large threshold more frequently. This imitated the effect of long-term spatial facilitation, elevating the neurons' initial depolarization so that even weak inputs could cause firing. Such gamma-distributed noise increased the overall excitability of the neural network as a modeled subsystem of the central nervous system. As the mean of the translated gamma distribution increased, neuronal activity tended rapidly to the pacemaker bursting type.