Amnesia - Causes

Causes

There are three generalized categories in which amnesia could be acquired by a person. 

The three categories are head trauma (example: head injuries), traumatic events (example: seeing something devastating to the mind), or physical deficiencies (example: atrophy of the hippocampus). 

The majority of amnesia and related memory issues derive from the first two categories as these are more common and the third could be considered a sub category of the first.

Head trauma is a very broad range as it deals with any kind of injury or active action toward the brain which might cause amnesia. 

Retrograde and Anterograde amnesia are more often seen from events like this, an exact example of a cause of the two would be electroshock therapy, which would cause both briefly for the receiving patient.

Traumatic events are more subjective. What is traumatic is dependent on what the person finds to be traumatic. 

Regardless, a traumatic event is an event where something so distressing occurs that the mind chooses to forget rather than deal with the stress. 

A common example of amnesia that is caused by traumatic events is dissociative amnesia, which occurs when the person forgets an event that has deeply disturbed them.

An example would be a person forgetting a fatal and graphic car accident involving their loved ones.

Physical deficiencies are different from head trauma as physical lean more toward passive physical issues. 

The difference would be having surgery that removes part of your brain, this would be active and thus head trauma, while the surgery caused the surrounding areas to atrophy, which is passive. 

Henry Molaison is a great example of physical deficiencies as parts of his brain began to atrophy after his surgery.

Amongst specific causes of amnesia are the following:

Electroconvulsive therapy

in which seizures are electrically induced in patients for therapeutic effect can have acute effects including both retrograde and anterograde amnesia.

Alcohol 

can both cause blackouts and have deleterious effects on memory formation.

Sources:        http://www.ask.com/wiki/Amnesia?lang=en

                        http://en.wikipedia.org/wiki/Amnesia

Amnesia - Discovery And Case Studies

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.

Sources:        http://www.ask.com/wiki/Amnesia?lang=en

                        http://en.wikipedia.org/wiki/Amnesia

Amnesia – General Introduction

Amnesia (from Greek ἀμνησία from ἀ- meaning "without" and μνήμη memory) is a deficit in memory caused by brain damage, disease, or psychological trauma. 

Amnesia can also be caused temporarily by the use of various sedatives and hypnotic drugs.

Essentially, amnesia is loss of memory.

The memory can be either wholly or partially lost due to the extent of damage that was caused.

There are two main types of amnesia: retrograde amnesia and anterograde amnesia.

Retrograde amnesia is the inability to retrieve information that was acquired before a particular date, usually the date of an accident or operation.

In some cases the memory loss can extend back decades, while in others the person may lose only a few months of memory.

Anterograde amnesia is the inability to transfer new information from the short-term store into the long-term store.

People with this type of amnesia cannot remember things for long periods of time. These two types are not mutually exclusive. Both can occur within a patient at one time.

Case studies, such as that of patient R.B., show that both types of amnesia can occur simultaneously.

Case studies also show that amnesia is typically associated with damage to the medial temporal lobe. In addition, specific areas of the hippocampus (the CA1 region) are involved with memory.

Research has also shown that when areas of the diencephalon are damaged, amnesia can occur.

Recent studies have shown a correlation between deficiency of RbAp48 protein and memory loss.

Scientists were able to find that mice with damaged memory have a lower level of RbAp48 protein compared to normal, healthy mice.

In people suffering with amnesia, the ability to recall immediate information is still retained, and they may still be able to form new memories.

However, a severe reduction in the ability to learn new material and retrieve old information can be observed.

Patients can learn new procedural knowledge.

In addition, priming (both perceptual and conceptual) can assist amnesiacs in the learning of fresh non-declarative knowledge.

Amnesic patients also retain substantial intellectual, linguistic, and social skills despite profound impairments in the ability to recall specific information encountered in prior learning episodes

Sources:        http://www.ask.com/wiki/Amnesia?lang=en

                        http://en.wikipedia.org/wiki/Amnesia