Disorders of memory

The following account concerns the approach to memory disorder adopted in clinical psychopathology. The psychology of memory disorder is discussed in Chapter

Memory may be differentiated into short-term or recent memory and long-term or remote memory. Furthermore, ultra-short-term memory may be distinguished from short-term memory. Ultra-short-term memory encompasses immediate registration within the span of attention. Short-term memory reflects new learning. Long-term memory is usually associated with earlier data or other information that has been stored for months or years.

A variety of additional terms are used to describe memory functions; for example, the contrasting terms of declarative and procedural memory appear to be useful. Declarative memory contains facts which may be consciously recalled, whereas procedural memory contains skills and automatic activities. In dementia—both degenerative (Alzheimer type) and vascular (multi-infarct dementia)—recent memory is usually impaired earlier than remote memory.

Biographical memory is the recall of events in a person's past which have an emotional loading and therefore has an impact on understanding depression.

Amnesia is a period of time which cannot be recalled and it may be global or partial. With regard to time it may be retrograde—an expression derived from the idea that one is looking backwards from an event (such as brain trauma or electroconvulsive therapy) to find the period before the event to be deleted. Correspondingly, anterograde amnesia means a period of deleted memory after an event. Although it is difficult to distinguish between types of amnesia, focal lesions in the hippocampus seem to affect remote memory less than recent memory, whereas diffuse brain disease often affects both. In psychogenic amnesia it is sometimes possible to recognize specific personal meaning in the events which cannot be recalled. (67) Bonhoeffer(68> regarded amnestic disorders to be 'purely exogenous', i.e. highly specific for a cerebral disorder. Although this is not true of psychogenic amnesia, amnestic disorders should nevertheless strongly alert the examiner to the possibility of cerebral pathology.

Disorders of memory are closely connected with other disorders, such as disorders of consciousness; there is often amnesia for episodes of disturbed consciousness.

Some patients are aware of memory disorder and complain about it; others tend to neglect their memory deficits and manifest secondary signs such as confabulations. Confabulations are inventions which substitute for missing contents in gaps of memory; the patient is not aware that they are not true memories.

A disorder of short-term memory, as in Korsakoff's syndrome or transient global amnesia, is often neglected by the patient. Behaviour appears normal, and one might say that the facade of personality is intact. Apparently, such a patient is engaged in lively conversation or seemingly purposeful actions, and only after further investigation does it become obvious that these activities are not based on facts. These forms of memory disorder can be assessed directly by examining the patient. Other forms become apparent retrospectively on taking the patient's history. In these cases the patient complains about periods of global or partial amnesia. Memory of certain events may have faded or become covered by layers of other events (palimpsest), which is typical of repeated amnestic periods following bouts of drinking. In mood disorder there may be complaints about impaired memory, although no memory deficit is found in objective tests. An example of false memories (paramnesia) is déjà vu, an erroneous feeling of familiarity with, for example, a person or a room. Déjà vu may occur in temporal lobe epilepsy, although it is not specific for that disorder. Delusional memories are also examples of paramnesia.

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