How memories form, fade, and persist over time - CNN.com
http://www.cnn.com/2009/HEALTH/01/28/memory.research/index.html

We all suffer occasional lapses in memory. Some people suffer severe neurological conditions, such as Alzheimer's, that rob them of their ability to form memories or remember recent events. Three new studies shed light on the way the brain forms, stores and retrieves memories. Experts say they could have implications for people with certain mental disorders.