Memory disorders are a reduction or loss of the ability to encode, retain, recognize, and reproduce information. There are several types of memory disorders:
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Amnesia: a condition in which memory is absent. Depending on the characteristics of amnesia, the following types are distinguished:
- Retrograde amnesia: loss of memory for events that occurred before the onset of the disorder.
- Anterograde amnesia: inability to form new memories after the onset of the disorder.
- Anteroretrograde amnesia: a mixed form combining loss of memory for past events and inability to form new memories.
- Delayed amnesia: memory is lost over time after the events occurred.
- Fixation amnesia: inability to form stable memories.
- Progressive amnesia: worsening of memory over time.
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Hypomnesia: weakening of memory. This may be caused by various diseases or be congenital.
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Paramnesias: types of memory distortions that include the following:
- Pseudomemory: a false memory of events or information believed to be real.
- Cryptomnesia: cases in which information seems to be perceived for the first time, but in fact it was known previously.
- Recognition: a false assertion that something has already been seen or has happened before.
Memory disorders may manifest not only as memory loss, but also as an inability to recognize familiar objects, which may be associated with the syndrome of agnosia. For example:
- Facial agnosia (prosopagnosia): inability to recognize faces.
- Letter agnosia: inability to recognize letters or words.
- Finger agnosia: inability to recognize fingers.
Memory disorders may also manifest in perceptual processes, such as failure to recognize familiar objects, which is part of the agnosia syndrome.
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