The purpose of this book is to describe the memory system of the brain, taking into account all the levels of neural organization: molecule, cell, small network, and anatomical circuit. This synthetic approach is necessary for determining the real mechanisms among the potential ones, that is the neural bases of learning and memory in intact organisms functioning under normal conditions. For this purpose, data from molecular, cellular and behavioral neurobiology, neuropsychology, animal and human psychology, and neural modellization are comprehensively reviewed by leading specialists and brought together in an original synthesis.