Amnesia (from Greek ἀμνησία from ἀ- meaning "without" and μνήμη memory)
is a deficit in memory caused by brain damage,
disease, or psychological trauma.
Essentially, amnesia is loss
of memory.
The memory can be either
wholly or partially lost due to the extent of damage that was caused.
There are two main types of
amnesia: retrograde amnesia and anterograde amnesia.
Retrograde amnesia is the
inability to retrieve information that was acquired before a particular date,
usually the date of an accident or operation.
In some cases the memory loss
can extend back decades, while in others the person 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 this type of
amnesia cannot remember things for long periods of time. These two types are
not mutually exclusive. Both can occur within a patient at one time.
Case studies, such as that
of patient R.B., show that both types of amnesia
can occur simultaneously.
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.
In people suffering with
amnesia, the ability to recall immediate information is still
retained, 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.
Patients can learn new
procedural knowledge.
In addition, priming (both
perceptual and conceptual) can assist amnesiacs in the learning of fresh non-declarative knowledge.
Amnesic patients also retain
substantial intellectual, linguistic, and social skills despite profound
impairments in the ability to recall specific information encountered in prior
learning episodes
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