100 Years after the discovery of Alzheimer's disease, neurological diseases and psychiatric disorders represent the largest and fastest growing unmet medical market with 2 billion affected people worldwide. Life expectancy of humans continues to increase, and the world population is aging. Advanced age may lead to deterioration of cognitive functions of the brain. There seems to be consensus that on the background of aging, several factors may render humans prone to dementia. Psychiatric and neurological disorders such as schizophrenia, bipolar disorder or Parkinson's disease may contribute to development of dementia. More people today are looking for help regarding their learning and memory capabilities. Although increasing knowledge on neuronal networks is transforming our view of the human brain and its function and we understand psychiatric and neurological diseases better today than ever before, novel therapies are needed to respond to the growing demand of patients for assistance with memory loss and learning impairment. In fact, it is expected that novel therapies aiming at the processing of amyloid, or at activation of glutamatergic or nicotinergic systems will demonstrate adequate efficacy in improving learning and memory disturbances. This publication stands as a comprehensive overview of the cellular and molecular mechanisms underlying the development of cognitive impairment. It integrates discoveries concerning dementia, such as mild cognitive impairment and Alzheimer's disease associated dementia, vascular dementia, retardation syndromes, and psychiatric and neurological disorders related cognitive impairments. This book will be useful to physicians, biologists, and those pursuing an interest or concerned with memory impairment.