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, 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. 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. 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.