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Main characteristics

Alzheimer's disease

Memory loss

Loss of memory can have consequences on daily life in many ways, leading to communication problems, safety hazards and behavioural problems. In order to understand how memory is affected by dementia, it is useful to consider the different kinds of memory.

Episodic Memory

This is the memory people have of events in their life ranging from the most mundane to the most personally significant. Within episodic memory, there are memories classed as short term (having happened in the last hour) and those classed as long term (having occurred more than an hour ago). People with Alzheimer's disease, at the beginning of the illness, do not seem to have any difficulty remembering distant events but may, for example, forget having done something five minutes ago. Memories of distant events although not greatly affected tend to interfere with present activities. This can sometimes result in the person acting out routines from the past which are no longer relevant.

Semantic Memory

This category covers the memory of what words mean, e.g. a flower or a dog. Unlike episodic memory, it is not personal, but rather common to all those who speak the same language. It is the shared understanding of what a word means, which enables people to having meaningful conversations. As episodic and semantic memory are not located in the same place in the brain, one may be affected and the other not.

Procedural Memory

Procedural Memory This is the memory of how to carry out actions both physically and mentally, for example, how to use a knife and fork or play chess. The loss of procedural memory can result in difficulties carrying out routine activities such as dressing, washing and cooking. This includes things which have become automatic. For this reason, some patients who have difficulty finding their words can still sing fairly well. Their procedural memory is still intact whereas their semantic memory (the meaning of words) has been damaged.

The Syndrome Apraxia - Aphasia - Agnosia


is the term used to describe the inability to carry out voluntary and purposeful movements despite the fact that muscular power, sensibility and coordination are intact. In everyday terms this might include the inability to tie shoelaces, turn a tap on, fasten buttons or switch on a radio.


is the term used to describe a difficulty or loss of the ability to speak or understand spoken, written or sign language as a result of damage to the corresponding nervous centre. This can become apparent in a number of ways. It might involve substituting a word which is linked by meaning (e.g. time instead of clock), using the wrong word but one which sounds similar (e.g. boat instead of coat) or use a completely different word with no apparent link. When accompanied by echolalia (the involuntary repetition of words or phrases spoken by another person) and the constant repetition of a word or phrase, the result can be a form of speech which is difficult for others to understand or a kind of jargon.


is the term used to describe the loss of the ability to recognise what objects are and what they are used for. For example, a person with agnosia might attempt to use a fork instead of a spoon, a shoe instead of a cup or a knife instead of a pencil etc. With regard to people, this might involve failing to recognise who people are, not due to memory loss but rather as a result of the brain not working out the identity of a person on the basis of the information supplied by the eyes.


People with Alzheimer's disease have difficulties both in the production and comprehension of language which in turn lead to other problems. Many patients also lose the ability to read and the ability to interpret signs.

Personality changes

People with Alzheimer's disease might behave totally out of character. A person who has always been quiet, polite and friendly might behave in an aggressive and ill-mannered way. Brusque and frequent mood changes are common.


A common symptom of Alzheimer's disease is wandering, both during the day and at night. There are a number of possible reasons for this wandering but due to communication problems, it is often impossible to find out what they are. Other symptoms affecting behaviour include incontinence, aggressive behaviour and disorientation in time and space

Physical changes

Weight loss can occur even when the normal intake of food is maintained. It can also occur as a result of the person forgetting to chew or how to swallow, particularly in the later stages of the illness. Another consequence of Alzheimer's disease is the wasting away of muscles and once bed-ridden there is the problem of bed sores. As people age, their vulnerability to infection increases. As a result of this increased vulnerability, many people with Alzheimer's disease die from pneumonia.



Last Updated: Wednesday 05 August 2009