Shakespeare called memory "the warder of the brain," charged with keeping watch over an individual's personal account of being. If this sentry begins to fail, a person's own record of self is endangered. This is a frightening prospect for most people. Memory loss can range from age-related impairment (a normal degree of forgetfulness) to several types of dementia (a loss of intellectual abilities, including memory, judgment, and abstract thinking).

Alzheimer's disease, the most common form of dementia, affects 5.3 million Americans and is the sixth leading cause of death in the United States. According to the Alzheimer's Association, by the year 2030 as many as 7.7 million Americans will be living with Alzheimer's disease if no effective prevention strategy or cure is found. By 2050 the number is projected to skyrocket to between 11 million and 16 million. Ten million baby boomers are expected to develop the disease.

Although Alzheimer's disease is irreversible, memory impairment associated with other conditions, such as depression or thyroid problems, may be correctable. Recent research advances leading to improved treatments for Alzheimer's disease offer reassuring news on that front as well.


People with amnesia suffer severe memory loss but have normal intelligence. The exotic nature of amnesia has long fascinated scientists and the public. In fact, research on a patient with amnesia provided the first direct evidence that structures in the temporal lobe (where the hippocampus is located) play an important role in memory.

Amnesia is caused by damage to the temporal lobes resulting from an accident, severe alcoholism, prolonged low blood pressure, or viral inflammation of the brain. Brain damage from such injuries usually results in anterograde amnesia—an inability to remember anything occurring after the injury. Retrograde amnesia—a loss of memory from a time prior to the accident, such as childhood—is rare.

Publication Review By: Peter V. Rabins, M.D., M.P.H.

Published: 07 Mar 2011

Last Modified: 28 Jan 2015