Amnesia

Written by Rachel Barclay | Published on October 8, 2013
Medically Reviewed by George Krucik, MD, MBA on October 8, 2013

What Is Amnesia?

Amnesia is a form of memory loss. Some people with amnesia have difficulty forming new memories. Others cannot recall facts and past experiences. People with amnesia usually retain knowledge of their own identity, as well as motor skills.

Mild memory loss is a normal part of aging. Significant loss of existing memories, or the inability to form new memories, could indicate the presence of an amnestic disorder.

Types of Amnesia

There are multiple types of amnesia:

Retrograde Amnesia

Retrograde amnesia is when existing memories are lost. It frequently affects recently formed memories. Older memories are affected more slowly. Diseases such as dementia cause gradual retrograde amnesia.

Anterograde Amnesia

Anterograde amnesia is when a person cannot form new memories. This effect can be temporary, such as in a blackout caused by too much alcohol. It can also be permanent, such as when a person has suffered damage to the area of the brain known as the hippocampus (which plays an important role in forming memories).

Transient Global Amnesia

Transient global amnesia (TGA) is a poorly understood condition. It is when a person experiences confusion or agitation that comes and goes repeatedly over the course of several hours. The person may experience memory loss in the hours before the attack and usually has no lasting memory of the experience. Scientists think that TGA occurs as the result of seizure-like activity or of a brief blockage of the blood vessels supplying the brain.

Causes of Amnesia

A memory’s location in the brain is thought to depend on the memory’s age (Costandi, M., 2009). To lose old memories, a person must experience widespread brain deterioration, such as the progressive memory loss due to Alzheimer’s disease or other forms of dementia. People with dementia usually lose more-recent memories first and keep older memories longer.

Anoxia (a depletion of oxygen levels) can also affect the whole brain, although if it is not severe enough to cause brain damage, the memory loss it causes can be temporary.

The hippocampus is responsible for forming new narrative memories, retrieving recently formed memories, and sending these new memories to become associated with the rest of the brain. Its cells are some of the brain’s most energy-hungry and fragile. They are most easily disrupted by anoxia, general anesthetic, toxins, and other threats. While the hippocampus is impaired, a person will have difficulty forming new memories. Stroke, tumors, and infection can cause permanent damage to the brain, including permanent memory problems.

If a person suffers damage to the hippocampus in both halves of the brain, such as from encephalitis, he or she can develop complete anterograde amnesia, which is the inability to form any new narrative memories.

Concussions commonly disrupt memories of the hours, days, or weeks before and after the injury.

Short-term alcohol use can cause blackout, a temporary form of anterograde amnesia. Long-term alcoholism can cause Wernicke-Korsakoff Syndrome. A person with this condition will have difficulty forming new memories but may not be aware of the fact.

A person who receives electroconvulsive therapy for depression or other conditions will usually experience retrograde amnesia of the weeks or months before their treatment.

Severe trauma or stress can cause dissociative amnesia, in which the mind rejects thoughts, feelings, or information that the person is too overwhelmed to handle.

Most people are unable to remember the first three to five years of life. This common phenomenon is called Infantile or childhood amnesia. 

How Is Amnesia Diagnosed?

Amnesia can be diagnosed by a physician or neural specialist.

A person with amnesia will have difficulty recalling facts, events, places, or specific details, such as that morning’s breakfast or the name of the current president. They will still retain their motor skills, such as the ability to walk, as well as fluency in any languages they speak.

How Is Amnesia Treated?

Treatment for amnesia usually consists of treating the underlying condition.

Chemically induced amnesia can be resolved by letting the person detoxify from the drug. Amnesia from concussion or other mild head trauma usually resolves over time. Amnesia from severe head injury may not recede. Improvement is usually seen by six to nine months (Kolb, et. al, 2003).

People with persistent memory loss can get occupational therapy to learn new information and memory skills to replace the missing or broken connections. Therapy also teaches techniques for organizing information to make it easier to retrieve, as well as the use of memory aids.

Preventing Memory Loss

The following healthy life practices may aid in preventing memory loss:

  • Avoid heavy use of alcohol or drugs.
  • Use protective headgear when engaging in sports that are at high risk for causing concussion.
  • Keep mentally active throughout life. For instance, take classes, explore new places, read new books, and play mentally challenging games.
  • Stay physically active throughout life.
  • Eat a heart-healthy diet including fruits, vegetables, whole grains, and low-fat proteins.
  • Stay hydrated.
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