Disorders of memory
Failure of memory is called amnesia. The related term dysmnesia is occasionally used, principally in the name of the dysmnesic syndrome, more often called the amnestic syndrome. Paramnesia is distortion of memory. Several kinds of disordered memory occur in psychiatric disorders, and it is usual to describe them in terms of two stages which approximate to the scheme of memory derived from psychological research but omit many of the details.
Immediate memory concerns the retention of information over a short period measured in minutes. It is tested clinically by asking the patient to remember a name and address (which they did not know before the test) and to recall it about 5 minutes later.
Recent memory concerns events in the last few days. It is tested clinically by asking about events in the patients daily life which are known also to the interviewer directly or via an informant (for example, what they have eaten) or in the wider environment (for example, well known news items).
Long term (remote) memory concerns events over longer periods of time. It is tested by asking about events before the presumed onset of memory disorder.
In testing any state of memory, a distinction is made between spontaneous recall and recognition of information. In some conditions, patients who cannot recall information can recognize it correctly.
Memory loss caused by organic conditions usually affects recall of recent events more than recall of distant ones, and it is not a total loss. Total loss of all memory including that of personal identity strongly suggests psychogenic causes or malingering. Some organic conditions give rise to an interesting partial effect known as amnestic disorder, in which the person is unable to remember events occurring a few minutes before, but can recall remote events. Some patients with memory disorder recall more when given cues. When this happens, it suggests that the disorder is concerned at least in part with retrieval.
After a period of unconsciousness, memory is impaired for the interval between the ending of complete unconsciousness and the restoration of full consciousness (anterograde amnesia). Some causes of unconsciousness (e.g. head injury and electroconvulsive therapy) lead also to inability to recall events before the onset of unconsciousness (retrograde amnesia).
Several disorders of recognition occur occasionally in neurological and psychiatric disorders:
. jamais vu is the failure to recognize events that have been encountered before;
. deja vu is the conviction that an event repeats one that has been experienced in the past when in fact it is novel;
. confabulation is the reporting as memories of events at one time, of events that took place at another time, or never involved the person.
Recall of events can be biased by the mood at the time of recall. Importantly, in depressive disorders, memories of unhappy events are recalled more readily than other events, a process which adds to the patient's low mood.