Memory has been widely defined as the information that islearned and stored inside of our brains.
There are three different established processesthat allow the retention of a memory within the brain. The first process isencoding, which is where information is gathered, collected and processed indifferent ways; the main ways being visually, acoustically and semantically.The semantic form refers to the application and association of a memory to ameaning. The secondary process begins in which, the information is stored intothe short term memory, and it stays there for a duration of time – one whichvary from individual to individual. If the particular memory is rehearsed, itis transferred into the long term memory of the brain. Finally, the last stageis retrieval; where information that is stored within the long term memory isthen retrievable on demand. Contrastingly, Amnesia is a term which refers to acondition in which the memories are not easily retrievable. This inabilityextends beyond the everyday forgetfulness and shows a failure at a certainpoint of the memory retention process mentioned beforehand.
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Amnesia can occurfor various different reasons, including neurological causes such as physicalinjury and psychogenic causes, like mental disorders or post-traumatic stress,even from alcohol abuse known as Korsakoff’s syndrome. This essay willarticulate our understanding of the connection between memory and amnesia andthe latter shaped the former. As previously stated, the two major storage systems ofmemory are the short term and long term memory.
The short term memory storesinformation for a more restricted period of time with a quite limited capacity.As opposed to the long term memory, which stores information for asignificantly longer duration with a potentially unlimited capacity. The limitof the capacity of the long term memory is unmeasurable, as the typical brainstores a vast variety ranging from language, grammar, etiquette, social norms,education as well as personal memories.
We understand the immensity more, particularlyif we look at an extreme of the spectrum – at individuals with photographicmemories, all the information they gather is all stored into their long termmemories for their entire lives. The other end of this spectrum is representedby those with amnesia who are often unable to retain or collect memory at all.This understanding of memory would not exist in such detail if not for thestudies of patients with conditions such as amnesia, which has provided betterinsight of the functionality of memory. These findings by psychologists haveenabled us to divide amnesia into types. The first type of amnesia is referred to as retrogradeamnesia, which is the inability to remember or retrieve past memories alreadystored within both the brain’s short and long term memory. The type of amnesiaenables us to separate the three processes that aid retention, identify andpinpoint where the brain is failing. This appears to occur within the finalprocess of retention; retrieval. Due tothe trauma, instead of the brain to allow access to these particular memorieson demand, it fails to locate them leaving those with this condition in varyingstates.
Some have lost only recent memory, from a few weeks to months and someare left without memory going on years. This memory loss is not only limited topersonal memories, patients have presented themselves with loss of language andinability to use their bodies. It is interesting to note that these memoriesare often not lost but rather hidden, and how re-immersing patients intofamiliar settings can trigger retrieval. Contrastingly, anterograde amnesia is described as the inability toacquire and retain new information, after the development of amnesia. This typeof amnesia represents a breakdown of the established processes of retentionstarting from the second step, as the brain completely lacks the ability totransfer the information into the long term memory.
Patients are able to gatherinformation, but this is retained for a significantly shorter period of time,even as short of a few mere seconds. Albeit, this is the worse of the two typesas it has no cure, but simultaneously it is the more interesting aspect ofamnesia as we are able to explore the other capabilities of the brain. The two main distinctions of long term memory aredeclarative/explicit memory and non-declarative/implicit memory. The formerstores information that require a conscious recollection. This memory can befurther divided into two sub-divisions: episodic memory and semantic memory.Episodic refers to memories of personal experiences including their time andthe location of these events.
Whilst the semantic memory retains knowledge wehave obtained through education such as worldly facts and history. Studies andobservations into the sub-divisions by Spiers et al (2001) found that the twowere distinctively different. He examined 147 cases of patients with amnesiawith damage to the hippocampus area, and discovered that there were impairmentsto episodic memory in all cases, however no substantial damage to the semanticmemory. However why this occurs is still being explored. On the other hand, non-declarativememory stores learned skills that can be retrieved unconsciously, allowingindividuals to perform actions by rote. This can also be subdivided into twocategories: procedural memory and priming. Procedural memory pertains to skillssuch as riding a bicycle or tying your shoelaces, these motor actions do notrequire any conscious thought or effort in most cases. Finally, priming refersto how the prior exposure of a stimulus affects the processing of a laterstimulus, both which share a relation.
For example, an individual who ispresented with an auditory stimulus of a dog allows a later auditory stimulus ofa dog to become easier to recognise, due to their connection. Thus, the firstaudio would be referred to as the prime, which aids the processing of the audiowhen presented the second time. Henry Gustav Molaison (1926-2008), familiarly known as H.M wasa patient suffering from amnesia, from whom studies were developed that wereparticularly influential in the development of the understanding of memory. Thepatient suffered from extreme epilepsy, that resulted in the surgical removalof his medial temporal lobe and parts of the hippocampus and amygdala. Throughthe surgery his epilepsy improved, however the consequences came in the form ofanterograde amnesia, that comprised his abilitiesto create new memories.
Despite his difficulty in forming new declarativememories, his procedural and short-term memory that Alan Baddeley (1974) refersto as the working memory, remained intact. Brenda Milner (1957) also learnedthat his digit span was completely normal she observed this when she tested hisability to repeat the numbers that spoke, which he was able to do perfectly –however his retention of those numbers was only for a number of few seconds,due to damage to his brain. Milner alsoexamined H.M’s motor skills by presenting him with a mirror-tracing task, wherehe would draw the outline of the images in front of him by merely looking atthe mirror. His task performance gradually improved over time as he was able tounconsciously retrieve this skill memory, however he was unable to actuallyremember learning or practicing it each time. This shows that perhaps there issome leak from the short term memory to the long term memory, particularly whenit comes to unconscious learned skills.
The observation of HM resulted in thebelief that the removal of or damage to the hippocampus, can result to adeficit in the long-term memory, . H.M was able to provide us with some of theearliest insights into anterograde amnesia and the case study shows thatlong-term memory is not necessarily indefinitely and only stored in thehippocampus since H.M was able to recall memories prior to his surgery.
To conclude, the various studies of amnesia have provided uswith crucial information that is key to developing evidential theories aboutmemory. Psychologists and Neurologists alike, have been able to systemicallydivide and organise the different sectors that the memory consists of, theirdifferences and the distinct way in which they work together to retaininformation. It has also aided in the understanding of the functionality of thebrain in relation to memory. Nonetheless, as our knowledge is predominatelybased on case studies and their findings, it is difficult to then generalise tothe wider population, as these studies are largely based on unique individualcases.A double disassociation in this case is where the short-termmemory and long-term memory are connected in a way where both can undergodamage separately but with the other still intact. Patients with amnesia typicallyexperience damage to their long-term memory as opposed to their short-termmemory.
This is generally caused by damage to the medial temporal lobe andimpairments to the short-term memory with unimpaired long-term memory areusually caused by damage to a different section, which include the parietal andtemporal lobes (Shallice and Warrington, 1974).