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Amnesia
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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