SYMPTOMS OF ALZHEIMER’S DISEASE: TEMPORAL LOBE CHANGES
April 2nd, 2009This is the part of the brain that appears to bear the brunt of the disease process and in many ways it often seems as if it is the seat of the abnormal changes which eventually spread out from here to involve the other structures. The earliest symptom of Alzheimer’s disease is usually memory loss and it is the temporal lobe and in particular a special structure within it called the hippocampus that are particularly associated with memory.
Memory is often divided into two types, classified as short-term and long-term memory by most people working in this field. It may be more accurate to use a slightly different concept, that of recent and remote memory. In this discussion recent or short-term memory will be used to refer to memory processes relating to the preceding hours or days, occasionally a little longer, while long-term or remote memory can go back as far as childhood.
The way in which memory is affected in Alzheimer’s disease is, in trade union manner, ‘last in, first out’. A quite severely demented person, particularly with Alzheimer’s, can often remember in detail activities that happened in childhood while having forgotten what he or she had for lunch, even though that may have been only half an hour earlier. Some people use short-term memory to refer to the type of memory that only lasts a few seconds and this also is severely affected.
It would seem as if memory normally works by transferring information from very short-term memory processes to longer-term memory processes and the major defect in Alzheimer’s disease may be an inability to store any new information. Not only is it more difficult to put it into the long-term memory store, but once there it doesn’t seem to last as long as information that was put there years before.
The consequence of this memory problem is the familiar picture of a sufferer from Alzheimer’s disease being unable to grasp what is said to him or her, needing to have items repeated, needing to write lists, forgetting to keep appointments, and so on. This can often lead to hazards in the home and as the dementing process advances it is not uncommon for relatives to discover that saucepans are put on the stove and allowed to boil dry, or gas taps turned on but not lit.
An example of this kind of behaviour is the person suffering from Alzheimer’s disease who went shopping in a nearby town, having driven ten miles from the village in which he lived. After completing as many of the purchases as he could remember and having got into difficulty in working out the change, he then set out to find his car to make the return journey home. Unfortunately, he could not find his car anywhere, decided it had been stolen, and managed to walk all the way home, turning up several hours late, having caused much distress to his wife. This example illustrates two aspects of memory. On the one hand he was unable to remember where he had parked his car, which was in fact only about thirty seconds’ walk from the store in which he had done most of his shopping; on the other hand the long journey home was sufficiently familiar to enable him to arrive back safely, although rather late. When questioned he said that he hadn’t been able to telephone his wife as he couldn’t remember their telephone number and he hadn’t been able to take a bus because he couldn’t remember the name of the village in which he lived; being unfamiliar with the bus service, he was unable to ask someone which bus he should take.
The pattern of memory loss, particularly the differentiation between very short-term (lasting only a few seconds) and longer but still relatively recent memory function, changes as the disease progresses, with the very short-term memory traces becoming more disturbed as the disease advances, whereas early on in the condition it is memory loss over a period of a few minutes or so that is most marked.
Doctors often try to test memory by asking questions that test the subjects’ ability to place themselves in the correct environment — space or time. The former is particularly affected by the context in which the question is asked. For instance questioning an Alzheimer’s disease sufferer after he or she has been moved to a hospital, clinic, or ward will frequently reveal disorientation in space, while the same question asked of him or her at home may elicit the correct answer.
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