Memories and Amnesic Case Studies: Analytical Essay

Within this assignment, I will discuss how amnesic case studies and in-depth analysis of such studies have helped us understand more about amnesia and the brain processes that may cause it. Theories of amnesia will be discussed as well as analysis of case studies and their importance to our knowledge of amnesia and how different areas of our brain may be involved. Amnesia is the term used to describe the partial or total loss of memories- including people, memorable events and facts you may have been taught. It is a type of brain damage that may be caused due to brain injury or a traumatic experience and leads to the person being unable to recall certain information from the past or be unable to create new memories. There are two main types of amnesia: anterograde amnesia- the person cannot remember new things but can remember old memories from before the trauma, and retrograde amnesia- the person cannot remember old events that happened before their trauma but can make new memories after the trauma. (Amnesia: Causes, Symptoms, and Treatments, 2020)

Different research into amnesia has provided evidence into which brain structures may influence our memory. One area that is very important to processing memories is the temporal lobe, it works with the other parts of the limbic system (hippocampus and amygdala) to form and store both long term and short-term memories. It was found that “patients with damage to the mesial and anterior portions of the temporal lobes suffer from a memory impairment involving both anterograde and retrograde amnesia” (Buccione, Serra, Caltagirone, carlesimo, 2008) therefore showing us the significance of the temporal lobe when it comes to memory processing both in the long and short term. Another important brain structure when it comes to memory is the hippocampus, as I will later talk about, is a vital structure when it comes to amnesic case studies. It is particularly important in the consolidation of information from short term to long term memory and many amnesic case studies such as HM and Clive Wearing involve damage to this area. (Brandt, Gardiner, Vargha-Khadem, Baddeley & Mishkin, 2009) The amygdala plays an important part in the modulation of memory consolidation. It uses our feelings at the time of an event to strengthen the memory, therefore if a memory has a strong emotional link it will be remembered more clearly. Research has been done where rats learn to associate a shock with a piece of apparatus so knows to avoid it, and when a drug was injected to stimulate the amygdala the rat had a much better memory for the apparatus. (Hatfield, T, Spanis, C and McGaugh, J, 2010) showing that feeling things such as pain may strengthen a memory allowing us to remember It more clearly.

Case studies are the in depth, thorough investigation of a person or event. They are often used in situations that are unique one offs and would be unethical to recreate just to study. Case studies are often a once in a lifetime opportunity, so researchers often take the opportunity to learn as much as possible from each case. The person or event being studied is usually an extremely rare circumstance therefore information gathered is not always helpful to the population as a whole and results found may also not be generalisable to the wider population. However, using case studies allows us to collect in the natural environment of the person or event and many different techniques can be used, such as interviews and experiments, often making data more valid. Data is also often collected over an extended period of time so changes to the subject can be seen and studied therefore expanding our knowledge even further.

One of the most well known case studies of amnesia today is the case of Henry Molaison, otherwise known as HM, who suffered severe memory impairment due to undergoing a bilateral, medial temporal-lobe resection to reduce his seizures which he had been having since the age of 10. The surgery removed large sections of his temporal lobes- which includes his hippocampus and amygdala. The operation was successful in reducing his major seizures, however, now post-surgery, HM had acquired severe anterograde amnesia, meaning he could no longer make new memories but he also suffered temporally graded retrograde amnesia meaning he no longer remembered anything from an 11 year period before his surgery. HM would repeat comments, forget what day it was, and when someone would turn away during conversation, he would forget who he was talking to. He was literally living in the present. (Corkin, 1984) However, due to HM’s willingness to be studied over the next 55 years of his life, his case provided researchers amazing insight into how our brains work. Before HM’s case, neuroscientists had thought of memory as a single entity, but now it was clear that there is a distinction between long term and short-term memory and that each one used different brain regions. In HM’s case, he no longer had his hippocampus and could no longer make new memories however he could recall a series of numbers if he constantly rehearsed them, showing that his short-term memory was intact, but his long-term memory wasn’t. This shows that the hippocampus must play an important role in the consolidation of memories from short to long-term.

Our declarative memory is the memory of things we have learnt, things such as phone numbers and capital cities, whereas our procedural memory is a type of unconscious memory that is involved in being able to perform different actions and skills, such as drawing and kicking a ball. Experiments done by Milner on HM showed us that these are two separate types of memory relying on different areas of the brain. HM’s procedural memory was perfectly fine, he was able to pick up new motor skills, even though he had no recollection of ever practising, showing us that his unconscious memory was able to remember things his conscious memory could not. Showing us therefore, that the hippocampus must play a part in declarative memory but not procedural. (Scoville and Milner, 1957) HM has played a vital role in providing knowledge of how and where the brain processes different types of memory, and without him who knows if we would even have half the amount of information that we have now.

Thanks to HM we found out a lot of information on the role of the hippocampus in memory processing however the case of KC proved that maybe there’s more to it than we realised. KC was involved in a motorcycle crash where he suffered “widespread brain damage that includes large bilateral hippocampal lesions”. (Tulving, 1993) He lost most of his old memories and was no longer able to make new memories, however it was discovered that KC could remember some of his past memories perfectly fine and they all fell into one category- they were all facts and knowledge. Tulving called these types of memories “semantic memories”. However, KC had lost all his personal memories and experiences or “episodic memories”. (Tulving, 1993) This suggests that episodic and semantic memories may be formed and stored separately, and therefore processed by different regions of the brain. The hippocampus helps record both types of memories at first, and it holds them until they are transferred. The hippocampus also helps us access old personal memories in long-term storage in other parts of the brain. But to access old semantic memories, the brain seems to use the parahippocampus, an extension of the hippocampus on the brain’s southernmost surface. K.C., whose parahippocampus survived, could therefore remember semantic knowledge like the rules of football (semantic knowledge) even though he had no recollection of ever playing football throughout his life, (episodic knowledge). (Kean, 2020) KC was incredibly important for validating and extending our knowledge of human memory processes. Although his case was similar to HMs and information about the hippocampus’ vital role to memory processing was confirmed, a whole lot of new information was discovered about our episodic and semantic memories that had only ever been theorised about before this case.

There are many theories of why we forget things, according to interference theory, we forget due to different memories interfering with each other. The more similar the memories the higher the chances of interference occurring. Unique personal events such as birthdays and holidays are less likely to be forgotten than your day at work last week where nothing out of the ordinary happened. Baddeley & Hitch (1977) investigated interference in sport. They tested rugby players’ memory of the names of players they had played against in that season. The players had played in different numbers of games. They found that players who had played in fewer games recalled more names than those who had played in the most games. This was attributed this to interference, suggesting that new memories may in fact replace older memories. However, Tulving & Psotka (1971) found that interference disappears when participants are given cued recall i.e. given clues such as category names. They concluded that the words had not actually been replaced as interference suggests but had been temporally forgotten and just needed some help to be remembered. Encoding specificity principle could explain this as it suggests that forgetting is cue dependant and that we don’t really forget things we just need a cue to trigger the memory. Abernathy (1940) found that psychology students performed better when tested by their usual teacher in the same room as they had learned the material, in this case the room acts as a cue triggering the students memory of the information allowing them to perform better. Although these studies provide some evidence to why we forget, nothing can be definitively proven, this is why case studies are essential to our learning of such complicated topics like memory.

Overall is it safe to say that amnesic case studies have played a vital role to our understanding of memory processes in the brain. Research has shown us the importance to the hippocampus to retaining memories for the long term, without it or even damage to it can have drastic effects to our memory. HM’s case could be described as revolutionary for neuroscientists looking into memory processes as his case was truly a once in lifetime situation. His willingness to be studied provided a great amount of insight into short term, long term, procedural and declarative memory and has allowed studies to progress to provide further information on memory. Not forgetting KC’s importance of identifying the different storage of semantic and episodic memories even further expanding our knowledge. Although these cases are only specific to each individual and it may be difficult to prove that everyone’s memory works in the same way, it is still a big step forwards in understanding our brain.