Memory memory and long-term memory. The short-term memory stores

Memory is information that is learned and stored in the
brain. There are three processes of remembering a memory. The first is
encoding, where information is gathered and processed in a visual, acoustic and
semantic form whereby you apply the memory with a meaning. The memory is then
stored in the short-term memory and if rehearsed, it is transferred into the
long-term memory. The last stage is retrieval; information that is in the
long-term memory can then be retrieved.


The two major storage systems for memory are the short-term
memory and long-term memory. The short-term memory stores information for only
a short amount of time with a limited capacity, whereas the long-term memory
stores information for a longer duration and with an unlimited capacity, this
includes a range of personal memories to general knowledge such as ability to
read and write.

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Amnesia is a condition that causes losses in the memory; it
may be the result of brain damage, neurological disease or even drug and
alcohol abuse known as Korsakoff’s syndrome.


Studying patients with brain damage such as amnesia has
provided psychologists with significant evidence and knowledge towards
developing a better insight of memory and its functions.


There are two main types of amnesia: retrograde amnesia and
anterograde amnesia. Retrograde amnesia is the inability to remember and
retrieve past memories. The memory loss varies between patients; some are
unable to recall information from only a short time ago e.g. a few weeks or
months, and others are unable to recall memories from years back. Anterograde
amnesia on the other hand is the inability to acquire and remember new
information after developing amnesia.


There are also two main distinctions of long-term memory:
declarative/explicit memory and non-declarative/implicit memory. Declarative
memory stores facts and events that require a conscious recollection. This
memory can also be further divided into two sub-divisions: episodic memory and
semantic memory. Episodic memory involves memories of personal experiences and
the time and place of specific events. Whereas, the semantic memory stores
facts and knowledge about the world that we have obtained. Non-declarative
memory stores learned skills that can be retrieved unconsciously, allowing
individuals to perform actions by rote. This can also be subdivided into two
categories: procedural memory and priming. Procedural memory includes skills
such as riding a bicycle, typing on a keyboard or tying your shoelaces, these
motor actions do not require any conscious thought or effort. Priming refers to
how the prior exposure of a stimulus affects the processing of a later
stimulus, both, which share a relation. For example, an individual who is
presented with an auditory stimulus of a dog allows a later auditory stimulus
of a dog easier to recognise, due to their connection. Thus, the first audio
would be referred to as the prime, which aids the processing of the audio when
presented the second time.


Henry Gustav Molaison (1926-2008) otherwise known as H.M was
an amnesic patient who was studied closely and was particularly influential in
the development of understanding memory. H.M suffered from extreme epilepsy,
which resulted in the surgical removal of the medial temporal lobe and parts of
the hippocampus and amygdala. Although his epilepsy improved, the surgery
created further complications HM was diagnosed with anterograde amnesia, which
causes impairments in creating future memories. Though he had difficulties in
forming new declarative memories and was unable to remember anyone after the
surgery, H.M’s procedural and short-term memory or as Alan Baddeley (1974)
refers to as ‘working memory’ remained unimpaired. Brenda Milner (1957) found
that he was able to immediately recall the exact numbers repeated by Milner,
however only for a number of seconds due to the short-term memory duration. Milner
also examined H.M’s motor skills by presenting him with a mirror-tracing task,
where he would draw the outline of the images in front of him by merely looking
at the mirror. His task performance gradually improved over time as he was able
to unconsciously retrieve this skill memory, however he was unable to actually
remember learning or practicing it each time. Therefore, the surgery that was
performed on H.M and the consequences he experienced subsequently allowed
greater understanding and the discovery of how specific areas of the brain are
related to certain memory types and the differences in memories. It is
suggested that the removal of or damage to the hippocampus can result to a
deficit in the long-term memory, however the case study of H.M shows that
long-term memory is not necessarily indefinitely stored in the hippocampus
since H.M was able to recall memories prior to his surgery.


As mentioned earlier, the two subdivisions that make up
declarative memory are episodic and semantic memory. Spiers et al (2001) found
that these two memories were distinctively different. He examined 147 cases of patients
with amnesia with damage to the hippocampus, and discovered that there were
impairments to episodic memory in all cases, however no substantial damage to
semantic memory.