Amnesia from brain trauma is part of the mechanism of memory formation.
Amnesia refers to the difficulty of retrieving stored information. There are three main types of amnesia: retrograde amnesia, anterograde amnesia, and infantile amnesia (general amnesia, whereby we lose old memories and have difficulty forming new ones, is very rare).
Brain trauma may be caused by injury, disease, malnutrition, stroke or alcohol/drug abuse, amongst other factors.
Retrograde amnesia results in the (partial) inability to retrieve information which has previously been stored. That is, memories from before the brain was damaged. Sufferers of retrograde amnesia are still capable of forming new memories. In general, more recent memories from before the damage become the hardest to retrieve. For example, an old man may have less difficulty in recounting his childhood than what he did two years ago – older memories have had longer to be encoded and effectively stored. Retrograde amnesia may be caused by stroke or brain tumours.
Comparatively, anterograde amnesia results in the (partial) inability to form new memories. That is, memories from after the brain was damaged. Sufferers of anterograde amnesia are still capable of retrieving old memories. Anterograde amnesia may be caused by damage to the temporal lobe or hippocampus.
Can you remember much from when you were aged one, two or three? Not many people can. If you do remember something very vividly from this time, it may be a reconstructed or ‘false’ memory. This is called infantile amnesia: the inability to recall memories from our early childhood. Infantile amnesia may be caused by the relatively slow development of the hippocampus.
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