Alzheimer's disease (AD), the most common form of neurodegenerative disorder in the elderly, is characterised pathologically by extracellular amyloid plaques and intracellular neurofibrillary tangles, pathophysiologically by synaptic dysfunction, and clinically by a progressive decline in cognition. Currently, AD has no cure and its prevalence is predicted to triple by 2050 with the rapid increase in the ageing population, unless more effective prevention/treatments are developed. Since the publication of the third book volume, the rapid progress in the research fields of AD and dementia continues through the intensive efforts of research scientists world-wide. This fourth book volume contains 12 chapters, bringing together a presentation of scientific frontiers in current AD/dementia research. The topics include emotional memory in AD, amyloid-B clearance, synaptic transmission-mediated regulation of amyloid-B dynamics, anti-AD immunotherapy, clinical trials of AD therapeutics using AD transgenic mouse models, roles of apolipoprotein E, chronic inflammation, cathepsins, and gelsolin in AD pathogenesis and as anti-AD therapeutic targets/agents, declarative memory impairment and hippocampal atrophy in Parkinson's disease, fronto-temporal dementia, and cognitive impairment in schizophrenia. These chapters cover current advances in our understanding of the pathogenic mechanisms underlying AD and dementia, in the diagnosis of early AD and dementia, and in the development of therapeutic agents that target memory-relevant AD pathogenesis. The book will be highly valuable to students and scientists world-wide who are interested in the scientific research progress in AD and memory disorders.