This book aims to provide a state-of-the-art summary of what is currently known about brain glycogen metabolism, detailing the recent advances in our understanding of why glycogen is so critical for normal brain function. The role of glycogen in cellular neurophysiology remains largely unclear and its specific contribution to the energy demand of brain cells is still elusive.Glycogen is the sole cerebral glucose reserve and is emerging as a fundamental component of brain energy metabolism. Pharmacological or genetic manipulation of glycogen metabolism in the brain impairs memory formation and increases susceptibility to epileptic seizures and cortical spreading depression. Glycogen is also directly implicated in abnormal neuronal excitability and mental retardation that characterize brain disorders like Lafora disease and Pompe disease.