Who am I?
Especially in comedies, characters often suffer from "amnesia"
after being bopped on the head. Typically, the person regains
consciousness with a puzzled expression and asks, "Who
am I? Where am I? How did I get there?"
Memento perpetuates the myth that amnesia is marked by a loss
of identity. In his travels, Shelby encounters a number of people
to whom he must explain his "condition." He tells
one of them, "I don't have amnesia. I know who I am. I
just can't form new memories." Although people with amnesia
do lose the ability to form memories-technically known as anterograde
amnesia-they do not forget who they are.
There is, however, a rare psychological phenomenon associated
with a loss of one's identity-so rare that some experts doubt
that it even exists. It's called fugue
state, defined in the textbooks as an "inability to
recall one's past and assumption of a new identity, which may
be partial or complete." Amnesia is about memory, not identity.
What is anterograde amnesia?
Leonard Shelby suffers from profound anterograde amnesia, which
is depicted accurately in the film. The disorder is marked by
an inability to create memories of facts and events. This is
often referred to as
declarative memory, consisting of what happened to you yesterday,
the name of someone you met on the street, the town you just
arrived in the previous day.
These are all examples of information that you recall and describe
(declare). To make up for his loss of declarative memory, Shelby
has facts essential to his investigation tattooed on his chest
and snaps numerous Polaroid photos of important places he's
been, people he has met, and things he has seen.
The memory bins
In explaining his condition, Shelby says he has "no short-term
memory." That's true:
Short-term memory is the bin in which we store recent experiences
and perceptions for minutes to hours while they are "consolidated"
into more enduring "long-term"
memories.
But what Shelby does have is working
memory: the bin that holds experiences for moments to seconds.
That means he can hold a conversation-as long as the other person
doesn't go on speaking for too long. In that case, Shelby might
forget where the conversation started, and become confused.
But like other people with anterograde amnesia, Shelby maintains
his intelligence, his ability to reason, make logical arguments,
express his thoughts, read a map, or keep a telephone number
"in mind" long enough to dial it.
The ghost of Patient HM
Shelby's predicament is familiar to anyone acquainted with the
famous case of "Patient HM." This man-his name is
kept confidential to protect his privacy-lost his ability to
form new memories in 1959. HM suffered from intractable epileptic
seizures in a region of the brain called the medial-temporal
lobes. To stop the dangerous electrical storms in HM's brain,
surgeons removed part of his medial-temporal lobes where the
storms originated.
In the process, HM lost two-thirds of his hippocampus,
a pair of pinkie-sized structures that are critical to the formation
of new memories. Like Leonard Shelby, patient HM wakes every
day with no memory of what took place the day before. He has,
however, maintained his older memories, those dating back to
before his operation.
Injured memories
Unlike patient HM, Shelby acquired his anterograde amnesia through
an accidental brain injury. This does happen, but it's much
more common for people to develop anterograde amnesia from a
stroke,
viral encephalitis,
chronic epilepsy,
or the interruption of the brain's oxygen supply due to near-drowning
or strangulation (hypoxia
or anoxia). These all may result in damage to the hippocampus,
which appears to be especially vulnerable to damage from oxygen
starvation. While it is conceivable that a blow to the head
could completely disable the hippocampus, it's not the way it
usually happens in real life.
Losing the past: retrograde amnesia
Another plot point in Memento that doesn't quite ring true is
his vivid memory of the physical attack in which he was injured.
People with anterograde amnesia often cannot remember the trauma
that caused their memory loss as well as some memories of events
just before the trauma. Scientists theorize that this loss of
past memories, or retrograde
amnesia, occurs because harm to the hippocampus has disrupted
the process of consolidation, by which recent memories are gradually
transformed into enduring long-term memories. The combination
of anterograde amnesia plus partial retrograde amnesia is quite
common. Collectively, it's often known as simply "amnesia."
Following procedure
One form of memory left intact in both Patient HM and the fictional
Shelby is the ability to learn skills. Called procedural
memory, it's what allows us to learn how to ride a bike,
play the piano, or swing a golf club properly. By performing
sets of actions (procedures), the brain forms a kind of unconscious
memory of the skills that you "just know how to do."
Areas of the brain outside the medial-temporal lobes are involved
in procedural memory, which is why an injury that results in
anterograde amnesia doesn't affect procedural memory.
Procedural memory is central to a subplot in Memento in which
Shelby flashes back to an insurance investigation he carried
out before his injury on a man claiming amnesia. Shelby wanted
to make sure the man wasn't "faking" his memory disorder.
The man, Sammy, undergoes a test in which he receives a small
electrical shock when he picks up a block of a certain shape.
In the film, Sammy repeatedly picks up the electrified block,
suggesting that his mind does not respond to what Shelby calls
"conditioning."
Even if he had amnesia, Sammy would typically associate something
negative with the shock block and avoid touching it, even though
he might not have been able to articulate exactly why. But Sammy
does not appear to have procedural memory. Shelby concluded
that Sammy's memory loss must have been psychological in nature,
not the result of a physical brain injury.
There is such a thing as psychological, or "psychogenic,"
memory loss. In response to a traumatic event-witnessing the
death of a loved one, being attacked-some people may "block
out" memory of the event as a coping mechanism. This usually
resolves with time and perhaps
psychotherapy.
Faking it
Real psychologists use a test for procedural memory to distinguish
between people with real amnesia and people who may be pretending
to have it. Fortunately it doesn't involve electric shocks-understandably,
a practice not allowed in real scientific research. The test
subject is given a list of words to read. Then after a short
delay, the tester asks the subject to recall the words. A person
with amnesia (or pretending to have amnesia) would naturally
be unable to remember the words accurately.
Then, the person is shown another list-one in which some of
the words from the previous list are intermixed with new words-and
asked if he recognizes any of them. A person with anterograde
amnesia will have poor word recall but will have near-normal
recognition of words seen previously.
Hollywood vs. Reality
To be fair, amnesia is often no more than a secondary plot device
in films, used to set up a mystery and draw the viewer in. But
in the real world, it's a rare and fascinating disorder that
has taught scientists much about the workings of human memory.
For all its minor technical mistakes, Memento is a high point
in the history of amnesia in film-if for no other reason that
it shows so dramatically the devastating effect of losing one's
ability to remember even the most mundane events of daily life.
FURTHER READING
Coping with Mild Traumatic Brain Injury, by
Diane Roberts Stoler and Barbara Albers Hill. (Avery Penguin
Putnam, 1998 (paperback), 284 pp., $14.95). This manual explains
the diagnosis, treatment, and rehabilitation of brain-injured
people and offers practical suggestions for coping with physical
and emotional consequences of brain injuries.
Brain Injury Association
105 N. Alfred Street
Alexandria VA 22314
800-444-6443
www.biausa.org
See the BIA's series of seven brochures, "The Road to
Rehabilitation,"
available free by request or on the organization's website.
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