Amnesia

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Amnesia is a deficit in memory caused by brain damage or brain diseases,^[1] but it can also be temporarily caused by the use of various sedative and hypnotic drugs. The memory can be either wholly or partially lost due to the extent of damage that is caused.^[2]

There are two main types of amnesia:

• Retrograde amnesia is the inability to remember information that was acquired before a particular date, usually the date of an accident or operation.^[3] In some cases, the memory loss can extend back decades, while in other cases, people may lose only a few months of memory.
• Anterograde amnesia is the inability to transfer new information from the short-term store into the long-term store. People with anterograde amnesia cannot remember things for long periods of time.

These two types are not mutually exclusive; both can also occur simultaneously.^[4]

Case studies also show that amnesia is typically associated with damage to the medial temporal lobe. In addition, specific areas of the hippocampus (the CA1 region) are involved with memory. Research has also shown that when areas of the diencephalon are damaged, amnesia can occur. Recent studies have shown a correlation between deficiency of RbAp48 protein and memory loss. Scientists were able to find that mice with damaged memory have a lower level of RbAp48 protein compared to normal, healthy mice.^[5][6] In people with amnesia, the ability to recall immediate information is still retained,^[7][8][9] and they may still be able to form new memories. However, a severe reduction in the ability to learn new material and retrieve old information can be observed. People can learn new procedural knowledge. In addition, priming (both perceptual and conceptual) can assist amnesiacs in the learning of fresh non-declarative knowledge.^[1] Individuals with amnesia also retain substantial intellectual, linguistic, and social skills despite profound impairments in the ability to recall specific information encountered in prior learning episodes.^[10][11][12]

The term is from Ancient Greek 'forgetfulness'; from ἀ- (a-) 'without', and μνήσις (mnesis) 'memory'.