Memory has been widely defined as the information that islearned and stored inside of our brains. Attkinson and Shiffron (1968) putforward the initial basic structure of the memory. It included three majorstores: the sensory store; short-term store and long-term store in whichinformation is passed through linearly. There are three different established processesby Melton (1963) that allow the retention of a memory within the brain.
Thefirst process is encoding, which is where information is gathered, collectedand processed in different ways; the main ways being visually, acoustically andsemantically. The semantic form refers to the application and association of amemory to a meaning. The secondary process begins in which, the information isstored into the short term memory, and it stays there for a duration of time –one which vary from individual to individual. If the particular memory isrehearsed, it is transferred into the long term memory of the brain. Finally,the last stage is retrieval; where information that is stored within the longterm memory is then retrievable on demand. Contrastingly, Amnesia is a termwhich refers to a condition in which the memories are not easily retrievable.This inability extends beyond the everyday forgetfulness and shows a failure ata certain point of the memory retention process mentioned beforehand. Amnesiacan occur for various different reasons, including neurological causes such asphysical injury and psychogenic causes, like mental disorders or post-traumaticstress, 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. The typeof amnesia enables us to separate the three processes that aid retention,identify and pinpoint where the brain is failing. This appears to occur withinthe final process of retention; retrieval.
Due to the trauma, instead of the brain to allow access to theseparticular memories on demand, it fails to locate them leaving those with thiscondition in varying states. Some have lost only recent memory, from a fewweeks to months and some are left without memory going on years. It isinteresting to note that these memories are often not lost but rather hidden,and how re-immersing patients into familiar settings can trigger retrieval.
Contrastingly, anterograde amnesia isdescribed as the inability to acquire and retain new information, after thedevelopment of amnesia. This type of amnesia represents a breakdown of theestablished processes of retention starting from the second step, as the braincompletely lacks the ability to transfer the information into the long termmemory. Patients are able to gather information, but this is retained for asignificantly shorter period of time, even as short of a few mere seconds.
Albeit, this is the worse of the two types as it has no cure, butsimultaneously it is the more interesting aspect of amnesia as we are able toexplore 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 stimulusof a dog to become easier to recognise, due to their connection. Thus, thefirst audio would be referred to as the prime, which aids the processing of theaudio when presented the second time. Henry Gustav Molaison (1926-2008), familiarly known as H.Mwas a patient suffering from amnesia, from whom studies were developed thatwere particularly influential in the development of the understanding ofmemory. The patient suffered from extreme epilepsy, that resulted in thesurgical removal of his medial temporal lobe and parts of the hippocampus andamygdala. Through the surgery his epilepsy improved, however the consequencescame in the form of anterograde amnesia, thatcomprised his abilities to create new memories. Despite his difficulty informing new declarative memories, his procedural and short-term memory thatAlan Baddeley (1974) refers to as the working memory, remained intact.
BrendaMilner (1957) also learned that his digit span was completely normal sheobserved this when she tested his ability to repeat the numbers that spoke,which he was able to do perfectly – however his retention of those numbers wasonly for a number of few seconds, due to damage to his brain. Milner also examined H.M’s motor skills bypresenting him with a mirror-tracing task, where he would draw the outline ofthe images in front of him by merely looking at the mirror. His taskperformance gradually improved over time as he was able to unconsciouslyretrieve this skill memory, however he was unable to actually remember learningor practicing it each time. This shows that perhaps there is some leak from theshort term memory to the long term memory, particularly when it comes tounconscious learned skills. The observation of HM resulted in the belief that theremoval of or damage to the hippocampus, can result to a deficit in thelong-term memory, . H.
M was able to provide us with some of the earliestinsights into anterograde amnesia and the case study shows that long-termmemory is not necessarily indefinitely and only stored in the hippocampus sinceH.M was able to recall memories prior to his surgery. A double disassociation was also established through thestudies of amnesia, in this case it is where the short-term memory andlong-term memory are connected in a way where both can undergo damage but withthe other still intact. Patients with amnesia typically experience damage totheir long-term memory with either little or no impairment to their short-termmemory. This is generally caused by damage to the medial temporal lobe andhippocampus, hence effecting episodic memory. It can also occur converselyhowever it is more rare; patients can undergo damage to the short-term memorywith unimpaired long-term memory.
This is usually caused by damage to theparietal and temporal lobes. In addition, semantic dementia patients lacksemantic memory retrieval whereas their episodic memory is unaffected. Incontrast amnesic patients have deficiency in episodic memory however theirsemantic memory remains rather in tact. 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.