What is amnesia?

Amnesia is loss of ability to memorise information and / or to recall information stored in memory. What we call memory, the ability to recollect our life’s experiences, is a very complex process within the brain. Researchers are only beginning to understand what exactly happens when we commit something to memory or when we try to remember it.

Not all memories are permanent, so merely being a little forgetful is not the same as having amnesia. Amnesia is a large-scale loss of memories that otherwise would be unlikely to be forgotten, such as important life experiences and people, or things you have just been taught or told.

Amnesia is often the symptom of a degenerative brain disease, such as Alzheimer’s disease, or may result from a traumatic injury to the brain. There has been much debate over whether the brain "blocks out" particularly traumatic memories.

What causes amnesia?

Amnesia is most commonly associated with either brain damage through injury or degeneration of brain cells in dementia. In both cases, brain cells are lost, and due to the complex network connecting cells within the human brain, they cannot be replaced. Most significant brain damage occurs when the brain is injured, such as in a car accident or as the result of a fall or blow. These traumas tend to cause a state of confusion, and some memory is often lost.

Infections that affect the brain, such as herpes or encephalitis may also cause memory loss. Severe alcohol or drug abuse, and malnutrition, act to deprive the brain of nutrients causing the death of brain cells. This can also cause significant loss of memories. Memory loss may sometimes result from stroke, if it affects the area of the brain concerned with memory functions.

Are there different types of amnesia?

Brain specialists tend to refer to three different types of amnesia:

  • Antegrade amnesia occurs when the patient cannot retain any new memories. This type of amnesia usually occurs after a brain injury, which forms the cut-off point for memories. The celebrated psychologist Oliver Sachs once had a patient who could not retain any memories after a brain operation in 1969. The patient had perfect recollection of his life before the operation, but could not retain any current memories and seemed frozen in the Sixties forever.
  • Retrograde amnesia is the case where, following a trauma, the patient is unable to recall important memories and information from before that event. The recent Hollywood movie, While You Were Sleeping, depicts a lawyer whose injury makes it difficult to recall events from before his accident.
  • Transient global amnesia is so-called because it only lasts for a short period of time, but affects a large portion of past memories. There is no known reason for such amnesiac attacks, but they can be extremely frightening for the patient, who may be without memories for up to 24 hours or more.

Most severe brain injuries cause a degree of retrograde amnesia and some post-traumatic confusion. The more severe the brain injury, the more serious the antegrade amnesia will be.

People suffering from Alzheimer’s disease commonly display deficiencies in their short term memories firstly. They may find it difficult to remember events that happened within the last few days while retaining excellent recall of events occurring earlier in their lives. This long term memory may be affected in advanced Alzheimer’s disease.

Can amnesia be cured?

Once brain cells die, they cannot be replaced. Depending on the cause of the amnesia, the brain may be able to recover many of its previous faculties, or may simply get worse. Those who have suffered brain loss as a result of an injury may see some improvement over time, as the brain attempts to heal itself. However, those whose amnesia is a symptom of a degenerative illness, such as Alzheimer’s disease, are unlikely to see an improvement.

Some forms of therapy have proven useful to amnesiacs in helping them to cope with their loss. Cognitive therapies in particular can help people regain skills that they have lost through amnesia.

The process of diagnosing the cause of amnesia involves conducting a series of tests. Anyone experiencing unexplained memory loss should consult their GP. If you suffer an accident that involves a blow to the brain, you should go to hospital immediately.

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