Memory is information that is learned and stored in thebrain. There are three processes of remembering a memory. The first isencoding, where information is gathered and processed in a visual, acoustic andsemantic form whereby you apply the memory with a meaning.
The memory is thenstored in the short-term memory and if rehearsed, it is transferred into thelong-term memory. The last stage is retrieval; information that is in thelong-term memory can then be retrieved. The two major storage systems for memory are the short-termmemory and long-term memory. The short-term memory stores information for onlya short amount of time with a limited capacity, whereas the long-term memorystores information for a longer duration and with an unlimited capacity, thisincludes a range of personal memories to general knowledge such as ability toread and write.
Amnesia is a condition that causes losses in the memory; itmay be the result of brain damage, neurological disease or even drug andalcohol abuse known as Korsakoff’s syndrome. Studying patients with brain damage such as amnesia hasprovided psychologists with significant evidence and knowledge towardsdeveloping a better insight of memory and its functions. There are two main types of amnesia: retrograde amnesia andanterograde amnesia.
Retrograde amnesia is the inability to remember andretrieve past memories. The memory loss varies between patients; some areunable to recall information from only a short time ago e.g. a few weeks ormonths, and others are unable to recall memories from years back. Anterogradeamnesia on the other hand is the inability to acquire and remember newinformation after developing amnesia. There are also two main distinctions of long-term memory:declarative/explicit memory and non-declarative/implicit memory.
Declarativememory stores facts and events that require a conscious recollection. Thismemory can also be further divided into two sub-divisions: episodic memory andsemantic memory. Episodic memory involves memories of personal experiences andthe time and place of specific events.
Whereas, the semantic memory storesfacts and knowledge about the world that we have obtained. 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 includes skillssuch as riding a bicycle, typing on a keyboard or tying your shoelaces, thesemotor actions do not require any conscious thought or effort. Priming refers tohow 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 easier to recognise, due to their connection. Thus, the first audiowould be referred to as the prime, which aids the processing of the audio whenpresented the second time.
Henry Gustav Molaison (1926-2008) otherwise known as H.M wasan amnesic patient who was studied closely and was particularly influential inthe development of understanding memory. H.M suffered from extreme epilepsy,which resulted in the surgical removal of the medial temporal lobe and parts ofthe hippocampus and amygdala.
Although his epilepsy improved, the surgerycreated further complications HM was diagnosed with anterograde amnesia, whichcauses impairments in creating future memories. Though he had difficulties informing new declarative memories and was unable to remember anyone after thesurgery, H.M’s procedural and short-term memory or as Alan Baddeley (1974)refers to as ‘working memory’ remained unimpaired. Brenda Milner (1957) foundthat 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.
Milneralso 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 lookingat the mirror. His task performance gradually improved over time as he was ableto unconsciously retrieve this skill memory, however he was unable to actuallyremember learning or practicing it each time. Therefore, the surgery that wasperformed on H.
M and the consequences he experienced subsequently allowedgreater understanding and the discovery of how specific areas of the brain arerelated to certain memory types and the differences in memories. It issuggested that the removal of or damage to the hippocampus can result to adeficit in the long-term memory, however the case study of H.M shows thatlong-term memory is not necessarily indefinitely stored in the hippocampussince H.M was able to recall memories prior to his surgery. As mentioned earlier, the two subdivisions that make updeclarative memory are episodic and semantic memory.
Spiers et al (2001) foundthat these two memories were distinctively different. He examined 147 cases of patientswith amnesia with damage to the hippocampus, and discovered that there wereimpairments to episodic memory in all cases, however no substantial damage tosemantic memory.
