Discovery
French psychologist Theodule-Armand Ribot was
among the first scientists to study amnesia.
He proposed Ribot's Law which
states that there is a time gradient in retrograde amnesia.
The law follows a
logical progression of memory-loss due to disease.
First, a patient loses the
recent memories, then personal memories, and finally intellectual memories.
He
implied that the most recent memories were lost first.
Important Case Studies
Case studies have played a
large role in the discovery of amnesia and the parts of the brain that were
affected.
The studies gave important insight into how amnesia affects the
brain.
The studies also gave scientists the resources into improving their
knowledge about amnesia and insight into a cure or prevention.
There are
several extremely important case studies: Henry Molaison, R.B, and G.D.
Henry Molaison
Henry Molaison,
formerly known as H.M., changed the way people thought of memory.
He was a
patient who suffered from severe epilepsy.
Physicians were unable to control
his seizures with drugs, so they tried a new approach involving brain surgery.
Doctors removed his medial temporal lobe bilaterally by doing a temporal
lobectomy.
His epilepsy did improve, but Molaison lost the ability to form new
long-term memories (anterograde amnesia).
He exhibited normal short-term memory
ability.
If he was given a list of words, he would forget them in about a
minute's time. In fact, he would forget that he was even given a list in the
first place.
Once Molaison stopped thinking
about the lists he was unable to recall them again from long term memory.
This
gave researchers evidence that short-term and long-term memory are in fact two
different processes.
Even though he forgot about the
lists, he was still able to learn things through his implicit memory.
The psychologists would ask him to draw something on a piece of paper, but to
look at the paper using a mirror.
Though he could never remember ever doing
that task, he would improve after doing it over and over again.
This showed the
psychologists that he was learning and remembering things unconsciously.
Studies were completed
consistently throughout Molaison’s lifetime to discover more about amnesia.
Researchers did a 14-year follow-up
study on Molaison.
They studied him for a period of two weeks to learn more
about his amnesia.
After 14 years, Molaison still could not recall things that
have happened since his surgery.
However, he could still remember things that
happened prior to the operation.
Researchers also found that, when asked,
Molaison could answer questions about national or international events, but he
could not remember his own personal memories.
After his death Molaison
donated his brain to science, where they were able to discover the areas of the
brain that had the lesions which caused his amnesia.
This case study provided
important insight to the areas of the brain that are affected in anterograde
amnesia, as well as how amnesia works.
Patient R.B.
Patient R.B. was a normally
functioning man up until the age of 52.
At Age 50 he had been diagnosed with
angina and had surgery for heart problems on two occasions.
After an ischemic
episode (reduction of blood to the brain) that was caused from a heart bypass
surgery, R.B. demonstrated a loss of anterograde memory, but almost no loss of
retrograde memory, with the exception of a couple of years before his surgery,
and presented no sign of any other cognitive impairment.
It wasn't until after
his death that researchers had the chance to examine his brain, when they found
his lesions were restricted to the CA1 portion of the hippocampus.
This case
study led to important research involving the role of the hippocampus and the
function of memory.
Patient G.D.
Patient G.D. was a white male
born in 1940 who served in the Navy. He was diagnosed with chronic renal
failure and received hemodialysis treatment for the rest of his life.
In 1983,
he went to the hospital for elective parathyroidectomy.
He also had a left thyroid
lobectomy because of the severe loss of blood in his left lobe.
He began having
cardiac problems as a result of the surgery and became very agitated.
Even five
days after being released from the hospital he was unable to remember what had
happened to him.
Aside from memory impairment, none of his other cognitive
processes seemed to be affected. He did not want to be involved in much
research, however, through memory tests he took with doctors, they were able to
ascertain that his memory problems were present for the next 9.5 years until
his death.
After he died, his brain was donated to science, photographed, and
preserved for future study.
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