This lecture provides an overview of dementia, focusing on its various types and the underlying neurobiological mechanisms. It begins with a clinical case presentation of Clive Wearing, who suffers from severe memory loss due to herpes encephalitis, illustrating the profound effects of memory disorders. The lecture then discusses learning disorders such as dyslexia, dysgraphia, and dyscalculia, highlighting their impact on cognitive function. It contrasts healthy aging with minimal cognitive impairment and delves into the typical changes in the brain associated with aging and dementia, particularly Alzheimer's disease. The instructor explains the symptoms of dementia, including memory loss, language problems, and disorientation, emphasizing that dementia is not a normal part of aging. The lecture concludes with a discussion on the pathophysiology of Alzheimer's disease, including amyloid plaques and tau tangles, and the importance of early diagnosis and intervention. Overall, the lecture aims to enhance understanding of dementia and its implications for individuals and society.