A A Spiking Model of Cell Assemblies: Short Term and Associative Memory

Cell Assemblies are the neural basis of both long and short term memories. Cell Assemblies, whose neurons persistently fire, are active short term memories while the neurons are firing, and the memory ceases to be active when the neurons stop firing. This paper provides simulations of excitatory spiking neurons with small world topologies that persist for several hundred milliseconds. Extending this model to include short term depression allows the Cell Assemblies to persist for several seconds, a reasonable psychological duration. These Cell Assemblies are combined in a simple associative memory so that when three Cell Assemblies are associated, ignition of two causes the third to ignite, while pairs of un-associated Cell Assemblies do not lead to the ignition of other Cell Assemblies. This mechanism has a larger capacity than a Hopfield net. The simulations provide a simple neurally based simulation model of short term and associative memory. A discussion of the current psychological theories, other mechanisms for short term memory, the strengths and weaknesses of the paper's simulated models, and proposed challenges are also provided.