Amnesia refers to the loss of memory. Memory loss may result from damage to parts of the brain vital for memory storage, processing, or recall (the limbic system, including the hippocampus in the medial temporal lobe). Amnesia can also be a symptom of neurodegenerative diseases. People whose primary symptom is memory loss (amnesiacs), typically retain their sense of self. They may even be aware that they suffer from a memory disorder.

Amnesia has several root causes. Most are traceable to brain injury related to physical trauma, disease, infection, drug and alcohol abuse, or reduced blood flow to the brain. In Wernicke-Korsakoff syndrome, for example, damage to the memory centers of the brain results from the use of alcohol or malnutrition. Infections that damage brain tissue, including encephalitis and herpes, can also cause amnesia. If the amnesia is thought to be of psychological origin, it is termed psychogenic. There...