The Tragic Effect of Amnesia Examined
The term Amnesia is the name given to disorders of memory.
Amnesia normally involves severe forgetfulness which goes beyond the everyday forgetting observed in normal people, to the extent that it may interfere with the activities of normal life.
We are all prone to moments of forgetfulness, but most people with intact cognitive functioning can remember quite a lot about the events in their lives, especially their most recent experiences and events which are important to them. However, a person suffering from amnesia may be quite unable to remember any recent events in their lives, even the most important ones.
|Case Study: Ronald Reagan|
As president of the United States Ronald Reagan was probably one of the most successful and powerful people of all time. But in 1994, a few years after he had left office, he was told that he had the early signs of Alzheimer’s disease, a progressive dementia which first destroys the memory and then all other cognitive abilities.|
Ronald Reagan announced the news in a brief handwritten letter to the American public. He wrote: ‘I have recently been told that I am one of millions of Americans who will be afflicted with Alzheimer’s disease. I now begin the journey that will lead me into the sunset of my life.’
Within three years Ronald Reagan’s memory had deteriorated so badly that he no longer remembered that he had once been the President of the United States. He was unable to understand why people waved at him in the street and why strangers seemed to know him and wished to shake his hand. He was also no longer able to recognize friends or former aides.
In 1997 he was visited by George Schultz, his former Secretary of State, but Mr Reagan did not seem to recognize his visitor, despite their many years of working closely together. However, it is possible that some glimmer of recognition remained, perhaps a slight feeling of familiarity somewhere below the level of conscious recollection. At one point during the visit the former president had returned to the room where his wife Nancy was chatting with Mr Schultz. Mr Reagan turned to his nurse and said, ‘Who is that man sitting with Nancy on the couch? I know him. He is a very famous man.’
You can probably recall quite easily where you were five minutes ago, or the person you just chatted with, or even what you did yesterday evening. Many amnesics (i.e., persons with amnesia) would be unable to remember these simple things, and may have no idea of what they have done with their day so far.
In severe cases they may be quite unable to commit any new experiences to memory, and this can be very disruptive to their lives. Without an intact memory it can become impossible to keep a job, to keep up relationships with family and friends, or even to look after oneself and maintain an independent existence. In fact, it is clear from the study of severely amnesic patients that memory is quite crucial to our ability to function properly as human beings.
Amnesia is a very disruptive and distressing condition. However, it is also a disorder from which a great deal can be learned about the nature of memory function.
Organic and Psychogenic Amnesia
Organic amnesia is caused by physical damage inflicted on the brain. This may arise from a variety of different causes, including brain infections, accidental injuries, and degenerative disorders such as Alzheimer’s disease. Organic amnesias tend to be severe and disabling, and they are also irreversible in the majority of cases because the brain lesion does not heal.
Psychogenic amnesias are quite different in their origin, as the causes are psychological and tend to involve the repression of disturbing memories which are unacceptable to the patient at some deep subconscious level. Psychogenic amnesias can be disorientating and disruptive to the patient, but they are rarely completely disabling, and as there is no actual brain damage they are reversible and in most cases will eventually disappear.
The organic amnesias are far more serious, and since they are also particularly instructive in helping us to understand the nature of memory function they will provide the main substance of this study.
The Aetiology (Causes) of Organic Amnesia
The term ‘aetiology’ refers to the origins and causative factors of a disorder. The main aetiologies of organic amnesia are summarized below.
Alzheimer’s Disease (AD)
Alzheimer’s disease (AD) is the most common cause of amnesia. It is a degenerative brain disorder which first appears as an impairment of memory, but later develops into a more general dementia, affecting all aspects of cognition. AD occurs mostly in the elderly, and in fact it is the main cause of senile dementia, eventually affecting as many as 20 per cent of elderly people.
Although seen mainly in people who are at least 60 or 70 years old, in rare cases AD may affect younger people, when it is referred to as pre-senile dementia. It was first identified by Alois Alzheimer (1907), though the cases he described in fact concerned the pre-senile form. It was only later realized that the same basic degenerative disorder, with its characteristic pattern of tangled neural fibers, was also responsible for most senile dementias. Since the amnesic symptoms of general dementia, they do not present a particularly pure form of amnesia and for this reason they are not the most widely researched amnesic group.
Korsakoff’s syndrome is a brain disease which usually results from chronic alcoholism, and it is mainly characterized by a memory impairment. It was first fully described by Korsakoff (1887), and it has become one of the most frequently studied amnesic conditions, mainly because it presents as a relatively pure form of amnesia without the complication of extensive dementia. However, recent studies have suggested that other cognitive functions besides memory may be impaired, though not usually to the extent seen in Alzheimer’s cases.
Herpes Simplex Encephalitis (HSE)
Herpes Simplex Encephalitis (HSE) is a virus infection of the brain, which can leave the patient severely amnesic. One important characteristic of HSE amnesia is its relatively sudden onset, which means that in many cases the date of onset of amnesic symptoms is known fairly precisely, in contrast to the very gradual onset of degenerative disorders such as Korsakoff and Alzheimer cases.
Temporal Lobe Surgery
A very small number of patients have become amnesic as a result of brain lesions caused by deliberate surgical procedures, usually involving the temporal lobes. Such cases are fortunately very rare, but they have been extensively studied because they provide a particularly valuable source of knowledge about memory. This is because the precise moment of onset of their amnesia is known, and furthermore the location and extent of their lesions is also known fairly accurately. One individual suffering from such temporal lobe amnesia, H.M. Opens in new window, has probably been more extensively investigated than any other amnesic patient (Scoville & Milner, 1957, Milner, 1966).
ECT (Electroconvulsive therapy) is a treatment used to alleviate depression, usually in patients who have failed to respond to any alternative form of therapy. ECT involves the administering of an electric shock across the front of the patient’s head, and it has been found that a period of amnesia may follow the administering of the shock.
Although it is possible that post-ECT amnesias are different in nature to the true organic amnesias, they have been widely investigated because they represent a serious side-effect of a deliberately administered treatment. It is therefore important for ethical reasons to establish the severity and duration of post ECT amnesia as part of the evaluation of the treatment.
Other Cases of Organic Amnesia
Since any condition which damages the appropriate areas of the brain can cause amnesia, there are many other possible causes, though none of them have been as widely studied as those listed above. For example, strokes and tumors can occasionally lead to amnesia, as can head injuries, brain damage caused by cardiac arrest, HIV infection, and degenerative conditions such as Huntington’s chorea and Parkinson’s disease.
- David Groome, Hazel Dewart, An Introduction to Cognitive Psychology: Processes and Disorders (p. 136-39) "Amnesia"