The fundamental mammalian behaviours of perception, recognition, recollection, and all other psychological phenomena are intrinsically related to the basic cognitive tasks of memorisation and association. Based on Hebb's Cell Assembly (CA) theory, it is believed that concepts are encoded as neuronal CAs in mammalian cortical areas. This paper describes a series of simulations that demonstrate various associative memory tasks using CAs based on biologically plausible fatiguing, Leaky, Integrate and Fire neurons. The simulations show the ability of CAs to form, retain and recollect basic concepts and multiple and sequential associations.