Long-term potentiation (LTP) is the most dominant model for neuronal changes that might encode memory. LTP is an elegant concept that meets many criteria set up by theoreticians long before the model's discovery, and also fits the anatomical data of learning-dependent synapse changes. Since the discovery of LTP, the question has remained regarding how closely LTP produced in vitro by artificial stimulation of neurons actually models putative learning-induced synaptic changes. A number of recent investigations have tried to correlate synaptic changes observed after learning with changes produced by artificial stimulation of neurons. Some of these studies have failed to find a correlation between the two forms of synaptic plasticity, signalling a need to discuss the concept of LTP and possible alternate processes that could fit the available data. This book presents a selection of ideas that range from supporters of the LTP theory to different novel concepts that have yet to be investigated. This volume will prepare the ground for research in this area in the new millennium.